SX1261 [SEMTECH]
Long Range, Low Power, sub-GHz RF Transceiver;
| 型号： | SX1261 |
| 厂家： | 
SEMTECH CORPORATION |
| 描述： | Long Range, Low Power, sub-GHz RF Transceiver |
| 文件： | 总107页 (文件大小：2366K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
SX1261/2
Long Range, Low Power, sub-GHz
RF Transceiver
Analog Front End & Data Conversion
TM
LoRa
Protocol
Engine
LNA
ADC
Modem
Matching
+
LPF
SPI
PA
PLL
FSK
Modem
Data
Buffer
OSC
DC-DC
LDO
Figure A: SX1261/2 Block Diagram
General Description
Applications
The level of integration and the low consumption within
SX1261/2 enable a new generation of Internet of Things
applications.
SX1261 and SX1262 sub-GHz radio transceivers are ideal for
long range wireless applications. Both devices are
designed for long battery life with just 4.2 mA of active
receive current consumption. The SX1261 can transmit up
to +15 dBm and the SX1262 can transmit up to +22 dBm
with highly efficient integrated power amplifiers.
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Smart meters
Supply chain and logistics
Building automation
Agricultural sensors
Smart cities
These devices support LoRa® modulation for LPWAN use
cases and (G)FSK modulation for legacy use cases. The
devices are highly configurable to meet different
application requirements utilizing the global LoRaWANTM
standard or proprietary protocols.
Retail store sensors
Asset tracking
The devices are designed to comply with the physical layer
requirements of the LoRaWANTM specification released by
Street lights
Parking sensors
the LoRa AllianceTM
.
Environmental sensors
Healthcare
The radio is suitable for systems targeting compliance with
radio regulations including but not limited to ETSI EN 300
220, FCC CFR 47 Part 15, China regulatory requirements
and the Japanese ARIB T-108. Continuous frequency
coverage from 150 MHz to 960 MHz allows the support of
all major sub-GHz ISM bands around the world.
Safety and security sensors
Remote control applications
SX1261/2
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Ordering Information
Part Number
Delivery
Minimum Order Quantity
SX1261IMLTRT
SX1262IMLTRT
Tape & Reel
Tape & Reel
3’000 pieces
3’000 pieces
QFN 24 Package, Pb-free, Halogen free, RoHS/WEEE compliant product.
Revision History
Version
ECO
Date
Modifications
1.0
039166
October 2017
First Release
Addition of a note “when using a TCXO" to explain the XTA cap value change
with TCXO in chapter 4.1.3 XTAL Control Block
New sub-chapter 5.1.5 “Considerations on the DC-DC Inductor Selection”
1.1
040046
December 2017
Addition of a note recommending 12 symbols of LoRa preamble for optimal
performances in chapter 6.1.1.1 Spreading Factor
Addition of a note on SetLoRaSymbNumTimeout in chapter 9.6 Receive Mode
Correction of RandomNumber Gen[] values in chapter 12.1 Register Map
SX1261/2
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Table of Contents
1. Architecture.....................................................................................................................................................................................................11
2. Pin Connection...............................................................................................................................................................................................12
2.1 I/O Description ..................................................................................................................................................................................12
2.2 Package View .....................................................................................................................................................................................13
3. Specifications..................................................................................................................................................................................................14
3.1 ESD Notice ...........................................................................................................................................................................................14
3.2 Absolute Maximum Ratings .........................................................................................................................................................14
3.3 Operating Range ...............................................................................................................................................................................14
3.4 Crystal Specifications ......................................................................................................................................................................15
3.5 Electrical Specifications ..................................................................................................................................................................15
3.5.1 Power Consumption ...........................................................................................................................................................16
3.5.2 General Specifications........................................................................................................................................................18
3.5.3 Receive Mode Specifications............................................................................................................................................19
3.5.4 Transmit Mode Specifications .........................................................................................................................................21
3.5.5 Digital I/O Specifications ...................................................................................................................................................21
4. Circuit Description.........................................................................................................................................................................................22
4.1 Clock References ...............................................................................................................................................................................22
4.1.1 RC Frequency References..................................................................................................................................................22
4.1.2 High-Precision Frequency Reference............................................................................................................................22
4.1.3 XTAL Control Block ..............................................................................................................................................................23
4.1.4 TCXO Control Block .............................................................................................................................................................24
4.2 Phase-Locked Loop (PLL) ...............................................................................................................................................................24
4.3 Receiver ................................................................................................................................................................................................25
4.3.1 Intermediate Frequencies.................................................................................................................................................25
4.4 Transmitter ..........................................................................................................................................................................................26
4.4.1 SX1261 Power Amplifier Specifics..................................................................................................................................27
4.4.2 SX1262 Power Amplifier Specifics..................................................................................................................................29
4.4.3 Power Amplifier Summary................................................................................................................................................31
5. Power Distribution........................................................................................................................................................................................32
5.1 Selecting DC-DC Converter or LDO Regulation ....................................................................................................................32
5.1.1 Option A: SX1261 with DC-DC Regulator ....................................................................................................................33
5.1.2 Option B: SX1261 with LDO Regulator .........................................................................................................................34
5.1.3 Option C: SX1262 with DC-DC Regulator ....................................................................................................................34
5.1.4 Option D: SX1262 with LDO Regulator.........................................................................................................................35
5.1.5 Consideration on the DC-DC Inductor Selection......................................................................................................35
5.2 Flexible DIO Supply .........................................................................................................................................................................36
6. Modems ............................................................................................................................................................................................................37
6.1 LoRa® Modem ....................................................................................................................................................................................37
6.1.1 Modulation Parameter .......................................................................................................................................................37
6.1.2 LoRa® Packet Engine ...........................................................................................................................................................39
6.1.3 LoRa® Frame...........................................................................................................................................................................40
6.1.4 LoRa® Time-on-Air................................................................................................................................................................41
6.1.5 LoRa® Channel Activity Detection (CAD) .....................................................................................................................41
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6.2 FSK Modem .........................................................................................................................................................................................42
6.2.1 Modulation Parameter .......................................................................................................................................................42
6.2.2 FSK Packet Engine................................................................................................................................................................43
6.2.3 FSK Packet Format ...............................................................................................................................................................44
7. Data Buffer .......................................................................................................................................................................................................47
7.1 Principle of Operation .....................................................................................................................................................................47
7.2 Data Buffer in Receive Mode ........................................................................................................................................................48
7.3 Data Buffer in Transmit Mode ......................................................................................................................................................48
7.4 Using the Data Buffer ......................................................................................................................................................................48
8. Digital Interface and Control.....................................................................................................................................................................49
8.1 Reset ......................................................................................................................................................................................................49
8.2 SPI Interface ........................................................................................................................................................................................49
8.2.1 SPI Timing When the Transceiver is in Active Mode................................................................................................49
8.2.2 SPI Timing When the Transceiver Leaves Sleep Mode ...........................................................................................50
8.3 Multi-Purpose Digital Input/Output (DIO) ..............................................................................................................................51
8.3.1 BUSY Control Line ................................................................................................................................................................51
8.3.2 Digital Input/Output ...........................................................................................................................................................53
8.4 Digital Interface Status versus Chip modes ............................................................................................................................53
8.5 IRQ Handling ......................................................................................................................................................................................54
9. Operational Modes .......................................................................................................................................................................................55
9.1 Startup ..................................................................................................................................................................................................55
9.2 Calibrate ...............................................................................................................................................................................................55
9.2.1 Image Calibration for Specific Frequency Bands......................................................................................................55
9.3 Sleep Mode .........................................................................................................................................................................................56
9.4 Standby (STDBY) Mode ..................................................................................................................................................................56
9.5 Frequency Synthesis (FS) Mode ..................................................................................................................................................57
9.6 Receive (RX) Mode ...........................................................................................................................................................................57
9.7 Transmit (TX) Mode .........................................................................................................................................................................58
9.7.1 PA Ramping............................................................................................................................................................................58
9.8 Active Mode Switching Time .......................................................................................................................................................58
9.9 Transceiver Circuit Modes Graphical Illustration ..................................................................................................................59
10. Host Controller Interface..........................................................................................................................................................................60
10.1 Command Structure .....................................................................................................................................................................60
10.2 Transaction Termination .............................................................................................................................................................60
11. List of Commands ......................................................................................................................................................................................61
11.1 Operational Modes Commands ................................................................................................................................................61
11.2 Register and Buffer Access Commands .................................................................................................................................62
11.3 DIO and IRQ Control ......................................................................................................................................................................62
11.4 RF, Modulation and Packet Commands .................................................................................................................................62
11.5 Status Commands ..........................................................................................................................................................................63
12. Register Map .................................................................................................................................................................................................64
12.1 Register Table ..................................................................................................................................................................................64
13. Commands Interface..................................................................................................................................................................................66
13.1 Operational Modes Functions ...................................................................................................................................................66
13.1.1 SetSleep.................................................................................................................................................................................66
13.1.2 SetStandby...........................................................................................................................................................................67
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13.1.3 SetFs........................................................................................................................................................................................67
13.1.4 SetTx .......................................................................................................................................................................................67
13.1.5 SetRx.......................................................................................................................................................................................68
13.1.6 StopTimerOnPreamble....................................................................................................................................................69
13.1.7 SetRxDutyCycle ..................................................................................................................................................................70
13.1.8 SetCAD...................................................................................................................................................................................72
13.1.9 SetTxContinuousWave.....................................................................................................................................................72
13.1.10 SetTxInfinitePreamble ...................................................................................................................................................73
13.1.11 SetRegulatorMode..........................................................................................................................................................73
13.1.12 Calibrate Function...........................................................................................................................................................73
13.1.13 CalibrateImage.................................................................................................................................................................74
13.1.14 SetPaConfig.......................................................................................................................................................................75
13.1.15 SetRxTxFallbackMode....................................................................................................................................................76
13.2 Registers and Buffer Access ........................................................................................................................................................77
13.2.1 WriteRegister Function....................................................................................................................................................77
13.2.2 ReadRegister Function.....................................................................................................................................................77
13.2.3 WriteBuffer Function ........................................................................................................................................................77
13.2.4 ReadBuffer Function.........................................................................................................................................................78
13.3 DIO and IRQ Control Functions .................................................................................................................................................78
13.3.1 SetDioIrqParams.................................................................................................................................................................78
13.3.2 IrqMask ..................................................................................................................................................................................78
13.3.3 GetIrqStatus.........................................................................................................................................................................79
13.3.4 ClearIrqStatus......................................................................................................................................................................80
13.3.5 SetDIO2AsRfSwitchCtrl....................................................................................................................................................80
13.3.6 SetDIO3AsTCXOCtrl ..........................................................................................................................................................80
13.4 RF Modulation and Packet-Related Functions ....................................................................................................................82
13.4.1 SetRfFrequency...................................................................................................................................................................82
13.4.2 SetPacketType.....................................................................................................................................................................82
13.4.3 GetPacketType....................................................................................................................................................................83
13.4.4 SetTxParams ........................................................................................................................................................................83
13.4.5 SetModulationParams......................................................................................................................................................84
13.4.6 SetPacketParams................................................................................................................................................................87
13.4.7 SetCadParams .....................................................................................................................................................................91
13.4.8 SetBufferBaseAddress ......................................................................................................................................................93
13.4.9 SetLoRaSymbNumTimeout............................................................................................................................................93
13.5 Communication Status Information .......................................................................................................................................94
13.5.1 GetStatus...............................................................................................................................................................................94
13.5.2 GetRxBufferStatus..............................................................................................................................................................95
13.5.3 GetPacketStatus .................................................................................................................................................................95
13.5.4 GetRssiInst ............................................................................................................................................................................96
13.5.5 GetStats .................................................................................................................................................................................96
13.5.6 ResetStats .............................................................................................................................................................................96
13.6 Miscellaneous ..................................................................................................................................................................................97
13.6.1 GetDeviceErrors..................................................................................................................................................................97
13.6.2 ClearDeviceErrors...............................................................................................................................................................97
14. Application ...................................................................................................................................................................................................98
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14.1 HOST API Basic Read Write Function ......................................................................................................................................98
14.2 Circuit Configuration for Basic Tx Operation .......................................................................................................................98
14.3 Circuit Configuration for Basic Rx Operation .......................................................................................................................99
14.4 Issuing Commands in the Right Order ...................................................................................................................................99
14.5 Application Schematics ............................................................................................................................................................ 100
14.5.1 Application Design of the SX1261 with RF Switch ............................................................................................. 100
14.5.2 Application Design of the SX1262 with RF Switch ............................................................................................. 100
15. Packaging Information........................................................................................................................................................................... 101
15.1 Package Outline Drawing ........................................................................................................................................................ 101
15.2 Package Marking ......................................................................................................................................................................... 102
15.3 Land Pattern ................................................................................................................................................................................. 102
15.4 Reflow Profiles .............................................................................................................................................................................. 103
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List of Figures
Figure 2-1: SX1261/2 Top View Pin Location QFN 4x4 24L................................................................................................................ 13
Figure 4-1: SX1261/2 Block Diagram.......................................................................................................................................................... 22
Figure 4-2: TCXO Control Block.................................................................................................................................................................... 24
Figure 4-3: PA Supply Scheme in DC-DC Mode ..................................................................................................................................... 27
Figure 4-4: VR_PA versus Output Power on the SX1261 .................................................................................................................... 27
Figure 4-5: Current versus Output Power with DC-DC Regulation on the SX1261................................................................... 28
Figure 4-6: Current versus Output Power with LDO Regulation on the SX1261........................................................................ 28
Figure 4-7: Power Linearity on the SX1261 with either LDO or DC-DC Regulation .................................................................. 29
Figure 4-8: VR_PA versus Output Power on the SX1262 .................................................................................................................... 29
Figure 4-9: Power Linearity on the SX1262.............................................................................................................................................. 30
Figure 4-10: Current versus Programmed Output Power on the SX1262 .................................................................................... 30
Figure 5-1: SX1261 Diagram with the DC-DC Regulator Power Option........................................................................................ 33
Figure 5-2: SX1261 Diagram with the LDO Regulator Power Option............................................................................................. 34
Figure 5-3: SX1262 Diagram with the DC-DC Regulator Power Option........................................................................................ 34
Figure 5-4: SX1262 Diagram with the LDO Regulator Power Option............................................................................................. 35
Figure 5-5: Separate DIO Supply.................................................................................................................................................................. 36
Figure 6-1: LoRa® Signal Bandwidth........................................................................................................................................................... 38
Figure 6-2: LoRa® Packet Format ................................................................................................................................................................. 40
Figure 6-3: Fixed-Length Packet Format .................................................................................................................................................. 44
Figure 6-4: Variable-Length Packet Format............................................................................................................................................. 44
Figure 6-5: Data Whitening LFSR................................................................................................................................................................. 45
Figure 7-1: Data Buffer Diagram .................................................................................................................................................................. 47
Figure 8-1: SPI Timing Diagram.................................................................................................................................................................... 49
Figure 8-2: SPI Timing Transition................................................................................................................................................................. 50
Figure 8-3: Switching Time Definition....................................................................................................................................................... 51
Figure 8-4: Switching Time Definition in Active Mode........................................................................................................................ 52
Figure 9-1: Transceiver Circuit Modes ....................................................................................................................................................... 59
Figure 13-1: Stopping Timer on Preamble or Header Detection..................................................................................................... 70
Figure 13-2: RX Duty Cycle Energy Profile................................................................................................................................................ 71
Figure 13-3: RX Duty Cycle when Receiving............................................................................................................................................ 72
Figure 14-1: Application Schematic of the SX1261 with RF Switch............................................................................................. 100
Figure 14-2: Application Schematic of the SX1262 with RF Switch............................................................................................. 100
Figure 15-1: QFN 4x4 Package Outline Drawing................................................................................................................................. 101
Figure 15-2: SX1261/2 Marking................................................................................................................................................................. 102
Figure 15-3: QFN 4x4mm Land Pattern.................................................................................................................................................. 102
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List of Tables
Table 2-1: SX1261/2 Pinout in QFN 4x4 24L ............................................................................................................................................ 12
Table 3-1: ESD and Latch-up Notice.......................................................................................................................................................... 14
Table 3-2: Absolute Maximum Ratings..................................................................................................................................................... 14
Table 3-3: Operating Range.......................................................................................................................................................................... 14
Table 3-4: Crystal Specifications ................................................................................................................................................................. 15
Table 3-5: Power Consumption.................................................................................................................................................................... 16
Table 3-6: Power Consumption in Transmit Mode ............................................................................................................................... 17
Table 3-7: General Specifications ................................................................................................................................................................ 18
Table 3-8: Receive Mode Specifications.................................................................................................................................................... 19
Table 3-9: Transmit Mode Specifications.................................................................................................................................................. 21
Table 3-10: Digital I/O Specifications ......................................................................................................................................................... 21
Table 4-1: Internal Foot Capacitor Configuration.................................................................................................................................. 23
Table 4-2: Intermediate Frequencies in FSK Mode ............................................................................................................................... 25
Table 4-3: Intermediate Frequencies in LoRa® Mode........................................................................................................................... 26
Table 4-4: Power Amplifier Summary ........................................................................................................................................................ 31
Table 5-1: Regulation Type versus Circuit Mode.................................................................................................................................... 32
Table 5-2: OCP Configuration ....................................................................................................................................................................... 32
Table 5-3: Typical 15 μH Inductors.............................................................................................................................................................. 35
Table 6-1: Range of Spreading Factors (SF) ............................................................................................................................................ 38
Table 6-2: Signal Bandwidth Setting in LoRa® Mode............................................................................................................................ 38
Table 6-3: Coding Rate Overhead ............................................................................................................................................................... 39
Table 6-4: Bandwidth Definition in FSK Packet Type ........................................................................................................................... 42
Table 6-5: Whitening Initial Value ............................................................................................................................................................... 45
Table 6-6: CRC Type Configuration............................................................................................................................................................. 46
Table 6-7: CRC Initial Value ............................................................................................................................................................................ 46
Table 6-8: CRC Polynomial............................................................................................................................................................................. 46
Table 8-1: SPI Timing Requirements........................................................................................................................................................... 50
Table 8-2: Switching Time.............................................................................................................................................................................. 52
Table 8-3: Digital Pads Configuration for each Chip Mode................................................................................................................ 53
Table 8-4: IRQ Status Registers..................................................................................................................................................................... 54
Table 9-1: SX1261/2 Operating Modes...................................................................................................................................................... 55
Table 9-2: Image Calibration Over the ISM Bands................................................................................................................................. 56
Table 9-3: Rx Gain Configuration................................................................................................................................................................. 57
Table 10-1: SPI Interface Command Sequence ...................................................................................................................................... 60
Table 11-1: Commands Selecting the Operating Modes of the Radio .......................................................................................... 61
Table 11-2: Commands to Access the Radio Registers and FIFO Buffer........................................................................................ 62
Table 11-3: Commands Controlling the Radio IRQs and DIOs.......................................................................................................... 62
Table 11-4: Commands Controlling the RF and Packets Settings ................................................................................................... 62
Table 11-5: Commands Returning the Radio Status............................................................................................................................. 63
Table 12-1: List of Registers ........................................................................................................................................................................... 64
Table 13-1: SetSleep SPI Transaction ......................................................................................................................................................... 66
Table 13-2: Sleep Mode Definition.............................................................................................................................................................. 66
Table 13-3: SetConfig SPI Transaction....................................................................................................................................................... 67
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Table 13-4: STDBY Mode Configuration ................................................................................................................................................... 67
Table 13-5: SetFs SPI Transaction ................................................................................................................................................................ 67
Table 13-6: SetTx SPI Transaction................................................................................................................................................................ 67
Table 13-7: SetTx Timeout Duration........................................................................................................................................................... 68
Table 13-8: SetRx SPI Transaction................................................................................................................................................................ 68
Table 13-9: SetRx Timeout Duration .......................................................................................................................................................... 69
Table 13-10: StopTimerOnPreamble SPI Transaction .......................................................................................................................... 69
Table 13-11: StopOnPreambParam Definition....................................................................................................................................... 69
Table 13-12: SetRxDutyCycle SPI Transaction......................................................................................................................................... 70
Table 13-13: SetCAD SPI Transaction......................................................................................................................................................... 72
Table 13-14: SetTxContinuousWave SPI Transaction........................................................................................................................... 72
Table 13-15: SendTxInfinitePreamble SPI Transaction........................................................................................................................ 73
Table 13-16: SetRegulatorMode SPI Transaction................................................................................................................................... 73
Table 13-17: Calibrate SPI Transaction ...................................................................................................................................................... 73
Table 13-18: Calibration Setting .................................................................................................................................................................. 74
Table 13-19: CalibrateImage SPI Transaction.......................................................................................................................................... 74
Table 13-20: SetPaConfig SPI Transaction................................................................................................................................................ 75
Table 13-21: PA Operating Modes with Optimal Settings.................................................................................................................. 75
Table 13-22: SetRxTxFallbackMode SPI Transaction ............................................................................................................................ 76
Table 13-23: Fallback Mode Definition...................................................................................................................................................... 76
Table 13-24: WriteRegister SPI Transaction ............................................................................................................................................. 77
Table 13-25: ReadRegister SPI Transaction.............................................................................................................................................. 77
Table 13-26: WriteBuffer SPI Transaction ................................................................................................................................................. 77
Table 13-27: ReadBuffer SPI Transaction .................................................................................................................................................. 78
Table 13-28: SetDioIrqParams SPI Transaction....................................................................................................................................... 78
Table 13-29: IRQ Registers.............................................................................................................................................................................. 79
Table 13-30: GetIrqStatus SPI Transaction ............................................................................................................................................... 79
Table 13-31: ClearIrqStatus SPI Transaction ............................................................................................................................................ 80
Table 13-32: SetDIO2AsRfSwitchCtrl SPI Transaction .......................................................................................................................... 80
Table 13-33: Enable Configuration Definition ........................................................................................................................................ 80
Table 13-34: SetDIO3asTCXOCtrl SPI Transaction ................................................................................................................................. 80
Table 13-35: tcxoVoltage Configuration Definition.............................................................................................................................. 81
Table 13-36: SetRfFrequency SPI Transaction......................................................................................................................................... 82
Table 13-37: SetPacketType SPI Transaction........................................................................................................................................... 82
Table 13-38: PacketType Definition............................................................................................................................................................ 82
Table 13-39: GetPacketType SPI Transaction.......................................................................................................................................... 83
Table 13-40: SetTxParams SPI Transaction............................................................................................................................................... 83
Table 13-41: RampTime Definition ............................................................................................................................................................. 83
Table 13-42: SetModulationParams SPI Transaction............................................................................................................................ 84
Table 13-43: GFSK ModParam1, ModParam2 & ModParam3 - br.................................................................................................... 84
Table 13-44: GFSK ModParam4 - PulseShape ......................................................................................................................................... 84
Table 13-45: GFSK ModParam5 - Bandwidth .......................................................................................................................................... 85
Table 13-46: GFSK ModParam6, ModParam7 & ModParam8 - Fdev .............................................................................................. 85
Table 13-47: LoRa® ModParam1- SF ........................................................................................................................................................... 86
Table 13-48: LoRa® ModParam2 - BW ........................................................................................................................................................ 86
Table 13-49: LoRa® ModParam3 - CR.......................................................................................................................................................... 86
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Table 13-51: SetPacketParams SPI Transaction...................................................................................................................................... 87
Table 13-52: GFSK PacketParam1 & PacketParam2 - PreambleLength......................................................................................... 87
Table 13-53: GFSK PacketParam3 - PreambleDetectorLength......................................................................................................... 87
Table 13-50: LoRa® ModParam4 - LowDataRateOptimize.................................................................................................................. 87
Table 13-54: GFSK PacketParam4 - SyncWordLength ......................................................................................................................... 88
Table 13-55: Sync Word Programming ..................................................................................................................................................... 88
Table 13-56: GFSK PacketParam5 - AddrComp...................................................................................................................................... 88
Table 13-57: Node Address Programming............................................................................................................................................... 88
Table 13-58: Broadcast Address Programming...................................................................................................................................... 89
Table 13-59: GFSK PacketParam6 - PacketType..................................................................................................................................... 89
Table 13-60: GFSK PacketParam7 - PayloadLength.............................................................................................................................. 89
Table 13-61: GFSK PacketParam8 - CRCType .......................................................................................................................................... 89
Table 13-62: CRC Initial Value Programming .......................................................................................................................................... 90
Table 13-63: CRC Polynomial Programming ........................................................................................................................................... 90
Table 13-64: GFSK PacketParam9 - Whitening ....................................................................................................................................... 90
Table 13-65: Whitening Initial Value .......................................................................................................................................................... 90
Table 13-66: LoRa® PacketParam1 & PacketParam2 - PreambleLength........................................................................................ 90
Table 13-67: LoRa® PacketParam3 - HeaderType .................................................................................................................................. 91
Table 13-68: LoRa® PacketParam4 - PayloadLength............................................................................................................................. 91
Table 13-69: LoRa® PacketParam5 - CRCType......................................................................................................................................... 91
Table 13-70: LoRa® PacketParam6 - InvertIQ........................................................................................................................................... 91
Table 13-71: SetCadParams SPI Transaction ........................................................................................................................................... 91
Table 13-72: CAD Number of Symbol Definition................................................................................................................................... 92
Table 13-73: Recommended Settings for cadDetPeak and cadDetMin with 4 Symbols Detection ................................... 92
Table 13-74: CAD Exit Mode Definition..................................................................................................................................................... 92
Table 13-75: SetBufferBaseAddress SPI Transaction ............................................................................................................................ 93
Table 13-76: SetLoRaSymbNumTimeout SPI Transaction.................................................................................................................. 93
Table 13-77: Status Bytes Definition........................................................................................................................................................... 94
Table 13-78: GetStatus SPI Transaction.................................................................................................................................................... 94
Table 13-79: GetRxBufferStatus SPI Transaction.................................................................................................................................... 95
Table 13-80: GetPacketStatus SPI Transaction ....................................................................................................................................... 95
Table 13-81: Status Bit ..................................................................................................................................................................................... 95
Table 13-82: GetRssiInst SPI Transaction .................................................................................................................................................. 96
Table 13-83: GetStats SPI Transaction ....................................................................................................................................................... 96
Table 13-84: GetDeviceErrors SPI Transaction........................................................................................................................................ 97
Table 13-85: OpError Bits................................................................................................................................................................................ 97
Table 13-86: ClearDeviceErrors SPI Transaction..................................................................................................................................... 97
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1. Architecture
The SX1261 and SX1262 (designated hereafter as “SX1261/2”) are half-duplex transceivers capable of low power operation
in the 150-960 MHz ISM frequency band. The radio comprises four main blocks:
1. Analog Front End: the transmit and receive chains, as well as the data converter interface to ensuing digital blocks.
The last stage of the transmit chain is different between the SX1261 and SX1262 chip versions. The SX1261 transceiver
is capable of outputting +14/15 dBm maximum output power under DC-DC converter or LDO supply. The SX1262
transceiver is capable of delivering up to +22 dBm under the battery supply.
2. Digital Modem Bank: a range of modulation options is available in the SX1261/2:
LoRa® Rx/Tx, BW = 7.8 - 500 kHz, SF5 to SF12, BR = 0.018 - 62.5 kb/s
(G)FSK Rx/Tx, with BR = 0.6 - 300 kb/s
3. Digital Interface and Control: this comprises all payload data and protocol processing as well as access to
configuration of the radio via the SPI interface.
4. Power Distribution: two forms of voltage regulation, DC-DC or linear regulator LDO, are available depending upon
the design priorities of the application.
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2. Pin Connection
2.1 I/O Description
Table 2-1: SX1261/2 Pinout in QFN 4x4 24L
Type
Pin
Pin
(I = input
Description
Number
Name
O = Ouptut)
0
1
GND
-
I
Exposed Ground pad
Input voltage for power amplifier regulator, VR_PA
SX1261: connected to pin 7
VDD_IN
SX1262: connected to pin 10
2
GND
XTA
-
Ground
3
-
Crystal oscillator connection, can be used to input external reference clock
4
XTB
-
Crystal oscillator connection
5
GND
-
Ground
6
DIO3
VREG
GND
I/O
Multipurpose digital I/O - external TCXO supply voltage
7
O
Regulated output voltage from the internal regulator LDO / DC-DC
8
-
Ground
9
DCC_SW
VBAT
VBAT_IO
DIO2
DIO1
BUSY
NRESET
MISO
MOSI
SCK
O
DC-DC Switcher Output
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
I
Supply for the RFIC
I
Supply for the Digital I/O interface pins (except DIO3)
I/O
Multipurpose digital I/O / RF Switch control
I/O
Multipurpose digital IO
I/O
Busy indicator
I/O
Reset signal, active low
O
I
SPI slave output
SPI slave input
I
SPI clock
NSS
I
SPI Slave Select
GND
-
Ground
RFI_P
RFI_N
RFO
I
RF receiver input
I
RF receiver input
O
-
RF transmitter output (SX1261 low power PA or SX1262 high power PA)
Regulated power amplifier supply
VR_PA
SX1261/2
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2.2 Package View
SCK
VDD_IN
GND
1
2
3
4
5
6
18
17
16
15
14
13
MOSI
MISO
XTA
0
GND
NRESET
XTB
BUSY
GND
DIO1
DIO3
Figure 2-1: SX1261/2 Top View Pin Location QFN 4x4 24L
SX1261/2
Data Sheet
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3. Specifications
3.1 ESD Notice
The SX1261/2 transceivers are high-performance radio frequency devices, with high ESD and latch-up resistance. The chip
should be handled with all the necessary ESD precautions to avoid any permanent damage.
Table 3-1: ESD and Latch-up Notice
Symbol
Description
Min
Typ
Max
Unit
Class 2 of ANSI/ESDA/JEDEC Standard JS-001-2014
(Human Body Model)
ESD_HBM
-
-
2.0
kV
ESD_CDM
LU
ESD Charged Device Model, JEDEC standard JESD22-C101D, class III
Latch-up, JEDEC standard JESD78 B, class I level A
-
-
-
-
1000
100
V
mA
3.2 Absolute Maximum Ratings
Stresses above the values listed below may cause permanent device failure. Exposure to absolute maximum ratings for
extended periods may affect device reliability, reducing product life time.
Table 3-2: Absolute Maximum Ratings
Symbol
Description
Min
Typ
Max
Unit
VDDmr
Tmr
Supply voltage, applies to VBAT and VBAT_IO
Temperature
-0.5
-55
-
-
-
-
3.9
125
10
V
°C
Pmr
RF Input level
dBm
3.3 Operating Range
Operating ranges define the limits for functional operation and parametric characteristics of the device. Functionality
outside these limits is not guaranteed.
Table 3-3: Operating Range
Symbol
Description
Min
Typ
Max
Unit
VDDop
Top
Supply voltage, applies to VBAT and VBAT_IO
Temperature under bias
1.8
-
-
-
-
-
3.7
85
V
°C
-40
Clop
ML
Load capacitance on digital ports
RF Input power
-
-
-
20
pF
dBm
-
0
VSWR
Voltage Standing Wave Ratio
10:1
SX1261/2
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3.4 Crystal Specifications
Table 3-4: Crystal Specifications
Symbol
Description
Min
Typ
Max
Unit
FXOSC
CLOAD
C0XTAL
RSXTAL
CMXTAL
DRIVE
Crystal oscillator frequency
Crystal load capacitance
Crystal shunt capacitance
Crystal series resistance
Crystal motional capacitance
Drive level
-
-
32
10
0.6
30
1.89
-
-
-
MHz
pF
0.3
-
2
pF
60
2.5
100
1.3
-
fF
W
The reference frequency accuracy is defined by the complete system, and should take into account precision of the
transmitter and the receiver, as well as environmental parameters such as extreme temperature limits. In a LoRaWANTM
system, the expected reference frequency accuracy on the end-device should be about +/- 30 ppm under all operating
conditions. This includes initial error, temperature drift and ageing over the lifetime of the product.
3.5 Electrical Specifications
The electrical specifications are given with the following conditions unless otherwise specified:
•
•
•
•
•
•
•
VBAT_IO = VBAT = 3.3 V, all current consumptions are given for VBAT connected to VBAT_IO
Temperature = 25 °C
FXOSC = 32 MHz, with specified crystal
FRF = 434/490/868/915 MHz
All RF impedances matched
Transmit mode output power defined in 50 load
FSK BER = 0.1%, 2-level FSK modulation without pre-filtering, BR = 4.8 kb/s, FDA = 5 kHz, BW_F = 20 kHz
double-sided
•
•
•
LoRa® PER = 1%, packet 64 bytes, preamble 8 symbols, CR = 4/5, CRC on payload enabled, explicit header mode
RX/TX specifications given using default RX gain step and direct tie connection between Rx and Tx
Blocking immunity, ACR and co-channel rejection are given for a single tone interferer and referenced to sensitivity +3
dB, blocking tests are performed with unmodulated signal
•
Optional TCXO and RF Switch power consumption always excluded
Caution!
Throughout this document, all receiver bandwidths are expressed as “double-sided bandwidth”. This is valid for
LoRa® and FSK modulations.
SX1261/2
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3.5.1 Power Consumption
Table 3-5: Power Consumption
Symbol
Mode
Conditions
Min
Typ
Max
Unit
OFF mode
(SLEEP mode
with cold start1)
IDDOFF
All blocks off
-
160
-
nA
SLEEP mode
(SLEEP mode
Configuration retained
-
-
600
1.2
-
-
nA
IDDSL
Configuration retained + RC64k
A
2
with warm start
)
IDDSBR
IDDSBX
STDBY_RC mode
RC13M, XOSC OFF
XOSC ON
-
-
0.6
0.8
-
-
mA
mA
STDBY_XOSC mode
Synthesizer mode
DC-DC mode used
LDO mode used
-
-
2.1
-
-
mA
mA
IDDFS
IDDRX
3.55
FSK 4.8 kb/s
-
-
-
-
4.2
4.6
4.8
5.3
-
-
-
-
mA
mA
mA
mA
LoRa® 125 kHz
Receive mode
Rx Boosted3, FSK 4.8 kb/s
Rx Boosted, LoRa® 125 kHz
DC-DC mode used
LoRa® 125 kHz, VBAT = 1.8 V
-
8.2
-
mA
FSK 4.8 kb/s
LoRa® 125 kHz
-
-
-
-
8
-
-
-
-
mA
mA
mA
mA
Receive mode
8.8
9.3
10.1
LDO mode used
Rx Boosted, FSK 4.8 kb/s
Rx Boosted, LoRa® 125 kHz
1. Cold start is equivalent to device at POR or when the device is waking up from Sleep mode with all blocks OFF, see Section 13.1.1 "SetSleep" on
page 66
2. Warm start is only happening when device is waking up from Sleep mode with its configuration retained, see Section 13.1.1 "SetSleep" on page
66
3. For more details on how to set the device in Rx Boosted gain mode, see Section 9.6 "Receive (RX) Mode" on page 57
SX1261/2
Data Sheet
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Table 3-6: Power Consumption in Transmit Mode
Symbol
Frequency Band
PA Match / Condition
Power Output
Typical
Unit
+14 dBm, VBAT = 3.3 V
+10 dBm VBAT = 3.3 V
+14 dBm, VBAT = 1.8 V
+10 dBm, VBAT = 1.8 V
25.5
18
mA
mA
mA
mA
+14 dBm
48
34
868/915 MHz
+15 dBm, VBAT = 3.3 V
+10 dBm VBAT = 3.3 V
+15 dBm, VBAT = 1.8 V
+10 dBm, VBAT = 1.8 V
32.5
15
mA
mA
mA
mA
+14 dBm / optimal settings 2
IDDTX
SX1261 1
60
29
+15 dBm, VBAT = 3.3 V
+14 dBm, VBAT = 3.3 V
+10 dBm, VBAT = 3.3 V
+15 dBm, VBAT = 1.8 V
+14 dBm, VBAT = 1.8 V
+10 dBm, VBAT = 1.8 V
25.5
21
mA
mA
mA
mA
mA
mA
14.5
46.5
39
434/490 MHz
+14 dBm
26
+22 dBm
+20 dBm
+17 dBm
+14 dBm
118
102
95
mA
mA
mA
mA
+22 dBm
90
868/915 MHz
+20 dBm / optimal settings 4
+17 dBm / optimal settings 4
+14 dBm / optimal settings 4
+20 dBm
+17 dBm
+14 dBm
84
58
45
mA
mA
mA
IDDTX
SX1262 3
+22 dBm
+20 dBm
+17 dBm
+14 dBm
107
90
mA
mA
mA
mA
+22 dBm
75
63
434/490 MHz
+20 dBm / optimal settings 4
+17 dBm / optimal settings 4
+14 dBm / optimal settings 4
+20 dBm
+17 dBm
+14 dBm
65
42
32
mA
mA
mA
1. For SX1261, DC-DC mode is used for the whole IC. For more details, see Section 5.1 "Selecting DC-DC Converter or LDO Regulation" on page 32.
2. For more details on optimal settings, see Section 13.1.14.1 "PA Optimal Settings" on page 75.
3. For SX1262, DC-DC mode is used for the IC core but the PA is supplied from VBAT. For more details, see Section 5.1 "Selecting DC-DC Converter or
LDO Regulation" on page 32.
4. Optimal settings adapted to the specified output power. For more details, see Section 13.1.14.1 "PA Optimal Settings" on page 75
SX1261/2
Data Sheet
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3.5.2 General Specifications
Table 3-7: General Specifications
Symbol
FR
Description
Conditions
Min
150
-
Typ
-
Max
960
-
Unit
MHz
Hz
Synthesizer frequency range
Synthesizer frequency step
SX1261
-
FSTEP
0.95
1 kHz offset
10 kHz offset
100 kHz offset
1MHz offset
10 MHz offset
-
-
-
-
-
-75
-95
-
-
-
-
-
dBc/Hz
dBc/Hz
dBc/Hz
dBc/Hz
dBc/Hz
Synthesizer phase noise
(for 868 / 915 MHz)
PHN1 2
-100
-120
-135
TS_FS
Synthesizer wake-up time
Synthesizer hop time
From STDBY_XOSC mode
10 MHz step
-
-
40
30
-
-
s
s
TS_HOP
Crystal oscillator
wake-up time
from STDBY_RC3
TS_OSC
-
150
-
-
s
Crystal oscillator trimming
range for crystal frequency
error compensation 4
OSC_TRM
min/max XTAL specifications
+/-15 +/-30
ppm
Programmable
300 5
200
BR_F
FDA
Bit rate, FSK
Frequency deviation, FSK
Bit rate LoRa®
0.6
0.6
-
-
-
kb/s
kHz
Minimum modulation index is 0.5
Programmable
FDA + BR_F / 2 250 kHz
Min. for SF12, BW_L = 7.8 kHz
Max. for SF5, BW_L = 500 kHz
62.5 6
BR_L
0.018
kb/s
500 6
12
BW_L
SF
Signal BW, LoRa®
Programmable
7.8
5
-
-
kHz
-
Spreading factor for LoRa®
Programmable, chips/symbol = 2^SF
Min/Max values in typical conditions,
Typ value for default setting
VDDop > VTCXO + 200 mV
Regulated voltage range for
TCXO voltage supply
VTCXO
1.6
1.7
3.3
V
Load current for
TCXO regulator
ILTCXO
-
-
1.5
-
4
mA
From enable to regulated voltage
within 25 mV from target
Start-up time for
TCXO regulator
TSVTCXO
100
s
Quiescent current
-
-
-
70
2
A
Current consumption of the
TCXO regulator
IDDTCXO
ATCXO
Relative to load current
1
%
provided through a 220 resistor
in series with a 10 pF capacitance
Amplitude voltage for
external TCXO
applied toXTA pin
0.4
0.6
1.2
Vpk-pk
See Section 4.2 "Phase-Locked Loop (PLL)" on
page 24
SX1261/2
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1. Phase Noise specifications are given for the recommended PLL BW to be used for the specific modulation/BR, optimized settings may be used for
specific applications
2. Phase Noise is not constant over frequency, due to the topology of the PLL, for two frequencies close to each other, the phase noise could change
significantly
3. Wake-up time till crystal oscillator frequency is within +/- 10 ppm
4. OSC_TRIM is the available trimming range to compensate for crystal initial frequency error and to allow crystal temperature compensation
implementation; the total available trimming range is higher and allows the compensation for all IC process variations
5. Maximum bit rate is assumed to scale with the RF frequency; for example 300 kb/s in the 869/915 MHz frequency bands and only 50 kb/s at 150
MHz
6. For RF frequencies below 400 MHz, there is a scaling between the frequency and supported BW, some BW may not be available below 400 MHz
3.5.3 Receive Mode Specifications
Table 3-8: Receive Mode Specifications
Symbol
Description
Conditions
Min
Typ
Max Unit
BR_F = 0.6 kb/s, FDA = 0.8 kHz, BW_F = 4 kHz
BR_F = 1.2 kb/s, FDA = 5 kHz, BW_F = 20 kHz
BR_F = 4.8 kb/s, FDA = 5 kHz, BW_F = 20 kHz
BR_F = 38.4 kb/s, FDA = 40 kHz, BW_F = 160 kHz
BR_F = 250 kb/s, FDA = 125 kHz, BW_F = 500 kHz
-
-
-
-
-
-125
-123
-118
-109
-104
-
-
-
-
-
dBm
dBm
dBm
dBm
dBm
Sensitivity 2-FSK,
RX Boosted gain, see Section 9.6
"Receive (RX) Mode" on page 57,
split RF paths for Rx and Tx, RF
switch insertion loss excluded
RXS_2FB
BW_L = 10.4 kHz, SF = 7
BW_L = 10.4 kHz, SF = 12
BW_L = 125 kHz, SF = 7
BW_L = 125 kHz, SF = 12
BW_L = 250 kHz, SF = 7
BW_L = 250 kHz, SF = 12
BW_L = 500 kHz, SF = 7
BW_L = 500 kHz, SF = 12
-
-
-
-
-
-
-
-
-134
-148
-124
-137
-121
-134
-117
-129
-
-
-
-
-
-
-
-
dBm
dBm
dBm
dBm
dBm
dBm
dBm
dBm
Sensitivity LoRa®,
Rx Boosted gain, see Section 9.6
"Receive (RX) Mode" on page 57,
split RF paths for Rx and Tx, RF
switch insertion loss excluded
RXS_LB
Sensitivity 2-FSK
Rx Power Saving gain
with direct tie connection
between Rx and Tx
RXS_2F
RXS_L
BR_F = 4.8 kb/s, FDA = 5 kHz, BW_F = 20 kHz
BW_L = 125 kHz, SF = 12
-
-115
-
dBm
Sensitivity LoRa®
Rx Power Saving gain
with direct tie connection
between Rx and Tx
-
-
-133
-9
-
-
dBm
dB
CCR_F
CCR_L
ACR_F
Co-channel rejection, FSK
Co-channel rejection, LoRa®
Adjacent channel rejection, FSK
SF = 7
-
-
5
-
-
dB
dB
SF = 12
19
Offset = +/- 50 kHz
-
45
-
dB
Offset = +/- 1.5 x BW_L
BW_L = 125 kHz, SF = 7
BW_L = 125 kHz, SF = 12
Adjacent channel rejection,
LoRa®
ACR_L
-
-
60
72
-
-
dB
dB
SX1261/2
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Table 3-8: Receive Mode Specifications
Symbol
Description
Conditions
Min
Typ
Max Unit
BR_F = 4.8 kb/s, FDA = 5 kHz, BW_F = 20 kHz
Offset = +/- 1 MHz
BI_F
-
-
-
68
70
80
-
-
-
dB
dB
dB
Blocking immunity, FSK
Offset = +/- 2 MHz
Offset = +/- 10 MHz
BW_L = 125 kHz, SF =12
Offset = +/- 1 MHz
Offset = +/- 2 MHz
Offset = +/- 10 MHz
-
-
-
88
90
99
-
-
-
dB
dB
dB
BI_L
Blocking immunity, LoRa®
Unwanted tones are 1 MHz and
1.96 MHz above LO
IIP3
IMA
3rd order input intercept point
Image attenuation
-
-5
-
dBm
Without IQ calibration
With IQ calibration
-
-
35
54
-
-
dB
dB
BW_F
TS_RX
DSB channel filter BW, FSK
Receiver wake-up time
Programmable, typical values
FS to RX
4.8
-
-
467
-
kHz
41
s
Maximum tolerated frequency
offset between transmitter and
receiver, no sensitivity
All bandwidths, 25% of BW
25%
BW
The tighter limit applies (see below)
degradation, SF5 to SF12
FERR_L
Maximum tolerated frequency
offset between transmitter and
receiver, no sensitivity
SF12
SF11
SF10
-50
-
-
-
50
ppm
ppm
ppm
-100
-200
100
200
degradation, SF10 to SF12
SX1261/2
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3.5.4 Transmit Mode Specifications
Table 3-9: Transmit Mode Specifications
Symbol
Description
Conditions
Min
Typ
Max
Unit
Highest power step setting
+14/15 1
+22
TXOP
Maximum RF output power
SX1261
SX1262
-
-
-
-
dBm
dBm
SX1261, under DC-DC or LDO
VDDop range from 1.8 to 3.7 V
-
0.5
-
dB
RF output power drop
versus supply voltage
TXDRP
SX1262, +22 dBm, VBAT = 2.7 V
SX1262, +22 dBm, VBAT = 2.4 V
SX1262, +22 dBm, VBAT = 1.8 V
-
-
-
2
3
6
-
-
-
dB
dB
dB
TXPRNG
TXACC
TXRMP
RF output power range
RF output power step accuracy
Power amplifier ramping time
Programmable in 31 steps, typical value
TXOP-31
-
TXOP
-
dBm
dB
-
2
-
Programmable
10
3400
s
36 + PA
ramping
TS_TX
Tx wake-up time
Frequency Synthesizer enabled
-
-
s
1. for SX1261 +15 dBm maximum RF output power can be reached with special settings, see Section 13.1.14.1 "PA Optimal Settings" on page 75.
3.5.5 Digital I/O Specifications
Table 3-10: Digital I/O Specifications
Symbol
Description
Conditions
Min
Typ
Max
Unit
0.7*VBAT_IO 1
VBAT_IO 1+0.3
VIH
VIL
Input High Voltage
Input Low Voltage
-
-
-
-
-
-
V
V
V
V
V
0.3*VBAT_IO 1
0.2*VBAT
-
-0.3
VIL_N
VOH
VOL
Input Low Voltage for pin NRESET
Output High Voltage
-
-0.3
0.9*VBAT_IO 1
0
VBAT_IO 1
Imax = -2.5 mA
0.1*VBAT_IO 1
Imax = 2.5 mA
-
Output Low Voltage
Digital input leakage current
(NSS, MOSI, SCK)
Ileak
-1
-
1
A
1. excluding following pins: NRESET and DIO3, which are referred to VBAT
SX1261/2
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4. Circuit Description
Analog Front End & Data Conversion
TM
LoRa
Protocol
Engine
LNA
ADC
Modem
Matching
+
LPF
SPI
PA
PLL
FSK
Modem
Data
Buffer
OSC
DC-DC
LDO
Figure 4-1: SX1261/2 Block Diagram
SX1261 and SX1262 are half-duplex RF transceivers operating in the sub-GHz frequency bands and can handle constant
envelope modulations schemes such as LoRa® or FSK.
4.1 Clock References
4.1.1 RC Frequency References
Two RC oscillators are available: 64 kHz and 13 MHz RC oscillators. The 64 kHz RC oscillator (RC64k) is optionally used by the
circuit in SLEEP mode to wake-up the transceiver when performing periodic or duty cycled operations. Several commands
make use of this 64 kHz RC oscillator (called RTC across this document) to generate time-based events. The 13 MHz RC
oscillator (RC13M) is enabled for all SPI communication to permit configuration of the device without the need to start the
crystal oscillator. Both RC oscillators are supplied directly from the battery.
4.1.2 High-Precision Frequency Reference
In SX1261/2 the high-precision frequency reference can come either from an on-chip crystal oscillator (OSC) using an
external crystal resonator or from an external TCXO (Temperature Compensated Crystal Oscillator), supplied by an internal
regulator.
The SX1261/2 comes in a small form factor 4 x 4 mm QFN package with the SX1262 able to transmit up to +22 dBm. When
in transmit mode the circuit may heat up depending on the output power and current consumption. Careful PCB design
using thermal isolation techniques must be applied between the circuit and the crystal resonator to avoid transferring the
heat to the external crystal resonator.
SX1261/2
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When using the LoRa® modulation with LowDataRateOptimize set to 0x00 (see Section Table 13-50: "LoRa® ModParam4 -
LowDataRateOptimize" on page 87), the total frequency drift over the packet transmission time should be minimized and
kept lower than Freq_drift_max:
When possible, using LowDataRateOptimize set to 0x01 will significantly relax the total frequency drift over the packet
transmission requirement to 16 x Freq_drift_max.
Note:
Recommendations for heat dissipation techniques to be applied to the PCB designs are given in detail in the application
note AN1200.37 “Recommendations for Best Performance” on www.semtech.com.
In miniaturized design implementations where heat dissipations techniques cannot be implemented or the use of the
LowDataRateOptimize is not supported, the use of a TCXO will provide a more stable clock reference.
4.1.3 XTAL Control Block
The SX1261/2 does not require the user to set external foot capacitors on the XTAL supplying the 32 MHz clock. Indeed, the
device is fitted with internal programmable capacitors connected independently to the pins XTA and XTB of the device.
Each capacitor can be set independently, balanced or unbalanced to each other, by 0.47 pF typical steps.
Table 4-1: Internal Foot Capacitor Configuration
Pin
Register Address
Typical Values
Each capacitor can be controlled independently
in steps of 0.47 pF added to the minimal value:
0x00 sets the trimming cap to 11.3 pF (minimum)
0x2F sets the trimming cap to 33.4 pF (maximum)
XTA
0x0911
XTB
0x0912
Note when using an XTAL:
At POR or when waking-up from Sleep in cold start mode, the trimming cap registers will be initialized at the value 0x05
(13.6 pF). Once the device is set in STDBY_XOSC mode, the internal state machine will overwrite both registers to the value
0x12 (19.7pF). Therefore, the user must ensure the device is already in STDBY_XOSC mode before changing the trimming
cap values so that they are not overwritten by the state machine.
Note when using a TCXO:
Once the command SetDIO3AsTCXOCtrl(...) is sent to the device, the register controlling the internal cap on XTA will be
automatically changed to 0x2F (33.4 pF) to filter any spurious which could occur and be propagated to the PLL.
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4.1.4 TCXO Control Block
Under certain circumstances, typically small form factor designs with reduced heat dissipation or environments with
extreme temperature variation, it may be required to use a TCXO (Temperature Compensated Crystal Oscillator) to achieve
better frequency accuracy. This depends on the complete system, transmitter and receiver. The specification FERR_L in
Section Table 3-8: "Receive Mode Specifications" on page 19 provides information on the maximum tolerated frequency
offset for optimal receiver performance.
Programmable DC
voltage 1.6 to 3.3 V
DIO3
100 nF
10 pF
1.5 to 4
mA
220 ꢀ
XTA
SX1261/SX1262
TCXO
XTB (leave open)
Figure 4-2: TCXO Control Block
When a TCXO is used, it should be connected to pin 3 XTA, through a 220 resistor and a10 pF DC-cut capacitor. Pin 4 XTB
should be left open. Pin 6 DIO3 can be used to provide a regulated DC voltage to power the TCXO, programmable from 1.6
to 3.3 V. VBAT should always be 200 mV higher than the programmed voltage to ensure proper operation.
The nominal current drain is 1.5 mA, but the regulator can support up to 4 mA of load. Clipped-sine output TCXO are
required, with the output amplitude not exceeding 1.2 V peak-to-peak. The commands to enable TCXO mode are described
in Section 13.3.6 "SetDIO3AsTCXOCtrl" on page 80, and that includes DC voltage and timing information.
Note:
A complete Reset of the chip as described in Section 8.1 "Reset" on page 49 is required to get back to normal XOSC
operation, after the chip has been set to TCXO mode with the command SetDIO3AsTCXOCtrl.
4.2 Phase-Locked Loop (PLL)
A fractional-N third order sigma-delta PLL acts as the frequency synthesizer for the LO of both receiver and transmitter
chains. SX1261/2 is able to cover continuously all the sub-GHz frequency range 150-960 MHz. The PLL is capable of
auto-calibration and has low switching-on or hopping times. Frequency modulation is performed inside the PLL
bandwidth. The PLL frequency is derived from the crystal oscillator circuit which uses an external 32 MHz crystal reference.
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4.3 Receiver
The received RF signal is first amplified by a differential Low Noise Amplifier (LNA), then down-converted to low- IF
intermediate frequency by mixers operating in quadrature configuration. The I and Q signals are low-pass filtered and then
digitized by a continuous time feedback architecture converter (ADC) allowing more than 80 dB dynamic range. Once
in the digital domain the signal is then decimated, down-converted again, decimated again, channel filtered and finally
demodulated by the selected modem depending on modulation scheme: FSK modem or LoRa® modem.
4.3.1 Intermediate Frequencies
The SX1261/2 receiver mostly operates in low-IF configuration, expect for specific high-bandwidth settings.
Table 4-2: Intermediate Frequencies in FSK Mode
Setting Name
Bandwidth [kHz DSB]
Intermediate Frequency [kHz]
RX_BW_467
RX_BW_234
RX_BW_117
RX_BW_58
RX_BW_29
RX_BW_14
RX_BW_7
467.0
234.3
117.3
58.6
29.3
14.6
7.3
250
250
250
250
250
250
250
200
200
200
200
200
200
200
167
167
167
167
167
167
167
RX_BW_373
RX_BW_187
RX_BW_93
RX_BW_46
RX_BW_23
RX_BW_11
RX_BW_5
373.6
187.2
93.8
46.9
23.4
11.7
5.8
RX_BW_312
RX_BW_156
RX_BW_78
RX_BW_39
RX_BW_19
RX_BW_9
312.0
156.2
78.2
39.0
19.5
9.7
RX_BW_4
4.8
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Table 4-3: Intermediate Frequencies in LoRa® Mode
BW Setting
Bandwidth [kHz DSB]
Intermediate Frequency [kHz]
LORA_BW_500
LORA_BW_250
LORA_BW_125
LORA_BW_62
LORA_BW_41
LORA_BW_31
LORA_BW_20
LORA_BW_15
LORA_BW_10
LORA_BW_7
500
250
0
250
250
250
167
250
167
250
167
250
125
62.5
41.67
31.25
20.83
15.63
10.42
7.81
4.4 Transmitter
The transmit chain uses the modulated output from the modem bank which directly modulates the fractional-N PLL. An
optional pre-filtering of the bit stream can be enabled to reduce the power in the adjacent channels, also dependent on
the selected modulation type.
The default maximum RF output power of the transmitter is +14/15 dBm for SX1261 and +22 dBm for SX1262. The RF
output power is programmable with 32 dB of dynamic range, in 1 dB steps. The power amplifier ramping time is also
programmable to meet regulatory requirements.
The power amplifier is supplied by the regulator VR_PA and the connection between VR_PA and RFO is done externally to
the chip. As illustrated in Figure 4-3: PA Supply Scheme in DC-DC Mode, the supply used for VR_PA is different between the
two circuit versions:
•
in SX1261: VR_PA, supplied through VDD_IN, is taken from a voltage regulator (DC-DC or LDO), allowing a very small
variation of the output power versus supply voltage;
•
in SX1262: VR_PA, supplied through VDD_IN, is taken directly from the battery and in this case maximum output
power is limited by supply voltage at VDD_IN.
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VBAT
VBAT
1.8 to 3.7 V
1.8 to 3.7 V
DCC_SW
DCC_SW
LDO DC-DC
(1.55 V)
LDO DC-DC
(1.55 V)
VREG (1.55 V)
VREG (1.55 V)
VDD_IN (1.8 to 3.7 V)
VDD_IN (1.55 V)
CORE
(RX)
CORE
(RX)
VR_PA (up to 1.35 V)
VR_PA (up to 3.1 V)
REG
PA
REG
PA
(PLL)
(PLL)
RFO
RFO
PA LP
PA LP
SX1261
SX1262
Figure 4-3: PA Supply Scheme in DC-DC Mode
4.4.1 SX1261 Power Amplifier Specifics
Caution!
All figures in this chapter are indicative and typical, and are not a specification. These figures only highlight
behavior of the PA over voltage and current.
In the SX1261, the power efficiency of the transmitter is maximized when the internal DC-DC regulator is used. The voltage
on VR_PA varies from about 20 mV to 1.35 V to achieve the programmed Output Power (Pout).
Figure 4-4: VR_PA versus Output Power on the SX1261
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With this method, the output power is kept almost constant with VBAT from 1.8 to 3.7 V.
When the DC-DC regulator is used the total power consumption will directly be impacted by the supply voltage. For
instance, when 17 mA are needed on VBAT to output +10 dBm with VBAT = 3.7 V, the same output and will require 34 mA
when VBAT = 1.8 V.
Figure 4-5: Current versus Output Power with DC-DC Regulation on the SX1261
However, when LDO is chosen, the current drain will remain flat for VBAT between 1.8 V and 3.7 V, at the expense of a much
lower energy efficiency:
Figure 4-6: Current versus Output Power with LDO Regulation on the SX1261
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The following plot also confirms the linearity of the output power curve at nominal and extreme voltage levels:
Figure 4-7: Power Linearity on the SX1261 with either LDO or DC-DC Regulation
4.4.2 SX1262 Power Amplifier Specifics
Caution!
All figures below are indicative and typical, and are not a specification. These figures only highlight behavior of the
PA over voltage and current.
Figures for the SX1262 are given with DC-DC regulation enabled, which applies only to the circuit core.
On the SX1262, the PA is optimized for maximum output power whilst maximizing the efficiency, which makes it
mandatory to supply the power amplifier with fairly high voltages to maintain an high output power. To summarize:
•
•
the current efficiency of the PA is optimal at the highest output power step
output power will be limited by the voltage supplied to VBAT.
This is illustrated in the following figure:
Figure 4-8: VR_PA versus Output Power on the SX1262
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The internal regulator for VR_PA has a little less than 200 mV of drop-out, which means VBAT must be 200 mV higher than
the published VR_PA voltages in order to attain the corresponding output power. For example, for P = +20 dBm, VR_PA
out
= 2.5 V is required, which means that the SX1262 will be able to maintain P = +20 dBm on the 2.7 V < VBAT < 3.7 V voltage
out
range. Below 2.7 V, the output power will degrade as VBAT reduces.
As can be seen from the blue curve on Figure 4-8: VR_PA versus Output Power on the SX1262, the SX1262 will be capable
of supplying almost 1.7 V when VBAT = 1.8 V, which, in turn, will make the output power plateau at +17 dBm for all power
settings above +17 dBm.
The following plot confirms the linearity of the output power, as long as the VBAT voltage is high enough to supply the
required VR_PA voltage:
Figure 4-9: Power Linearity on the SX1262
The power consumption evolves with the programmed output power, as follows (DC-DC regulation):
Figure 4-10: Current versus Programmed Output Power on the SX1262
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4.4.3 Power Amplifier Summary
The following table summarizes the power amplifier optimization keys in the SX1261 and SX1262 transceivers:
Table 4-4: Power Amplifier Summary
PA Summary
Conditions
SX1261
SX1262
with relevant matching and
settings
Max Power
+14 /15 dBm
+ 22 dBm
118 mA
90/451 mA
at + 22 dBm, indicative
at + 14 dBm, indicative
-
IDDTX
25.5 mA
flat from 3.3 V to 3.7 V
VBAT = 3.1 V for +22 dBm
VBAT = 2.7 V for +20 dBm
VBAT = 1.8 V for +16 dBm
Output Power vs VBAT
flat from VBAT = 1.8 V to 3.7 V
inversely proportional to VBAT,
DC - DC buck converter
is used for PA supply
IDDTX vs VBAT
-
1. See Section 13.1.14.1 "PA Optimal Settings" on page 75.
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5. Power Distribution
5.1 Selecting DC-DC Converter or LDO Regulation
Two forms of voltage regulation (DC-DC buck converter or linear LDO regulator) are available depending upon the design
priorities of the application. The linear LDO regulator is always present in all modes but the transceiver will use DC-DC when
selected. Alternatively a high efficiency DC to DC buck converter (DC-DC) can be enabled in FS, Rx and Tx modes.
The DC-DC can be driven by two clock sources:
•
in STDBY_XOSC: RC13M is used to supply clock and the frequency is RC13M / 4 so the switching frequency of the
DC-DC converter will be 3.25 MHz
•
in FS, RX, TX: the PLL is used to supply clock and the frequency is ~5MHz; every time the command SetRFFrequency(...)
is called the divider ratio is recalculated so that the switching frequency is as close as possible to the 5 MHz target.
Unless specified, all specifications of the transceiver are given with the DC-DC regulator enabled. For applications where
cost and size are constrained, LDO-only operation is possible which negates the need for the 47nH inductor before pin 1
and the 15 μH inductor between pins 7 and 9, conferring the benefits of a reduced bill of materials and reduced board
space. The following table illustrates the power regulation options for different modes and user settings.
Table 5-1: Regulation Type versus Circuit Mode
Circuit Mode
Sleep
STDBY_RC STDBY_XOSC
FS
Rx
Tx
Regulator Type = 0
Regulator Type = 1
-
-
LDO
LDO
LDO
LDO
LDO
LDO
DC-DC + LDO
DC-DC + LDO
DC-DC + LDO
DC-DC + LDO
The user can specify the use of DC-DC by using the command SetRegulatorMode(...). This operation must be carried out in
STDBY_RC mode only.
When the DC-DC is enabled, the LDO will remain On and its target voltage is set 50 mV below the DC-DC voltage to ensure
voltage stability for high current peaks. If the DC-DC voltage drops to this level due to high current peak, the LDO will cover
for the current need at the expense of the energy consumption of the radio which will be increased.
However, to avoid consuming too much energy, the user is free to configure the Over Current Protection (OCP) register
manually. At Reset, the OCP is configured to limit the current at 60 mA.
Table 5-2: OCP Configuration
Circuit
Register Address
OCP default
Maximum Current
SX1261
SX1262
0x08E7
0x08E7
0x18
0x38
60 mA
140 mA
The OCP is configurable by steps of 2.5 mA and the default value is re-configured automatically each time the function
SetPaConfig(...) is called. If the user wants to adjust the OCP value, it is necessary to change the register as a second step after
calling the function SetPaConfig(...).
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Note:
The user should pay attention to the dependency of the current drain versus VBAT when using the SX1261 in DC-DC mode.
Because the current drained is inversely proportional to VBAT (for instance for P = +14 dBm, 25.5 mA at 3.3 V, and 48 mA
out
at 1.8 V), the OCP current limit should be set high enough to accommodate a current increase or be dynamically set.
Another strategy is to set the OCP to a specific limit and accept a drop of the output power of the device when the OCP
starts limiting the current consumption.
5.1.1 Option A: SX1261 with DC-DC Regulator
The DC-DC Regulator is used with about 90% of
efficiency, for the chip core and Power Amplifier (PA).
Advantage of this option:
VDD_IN
The power consumption is drastically reduced at 3.3 V,
output power is maintained from VBAT = 1.8 V to 3.7 V.
SX1261
Main supply
1.8 to 3.7 V
Figure 5-1: SX1261 Diagram with the DC-DC Regulator Power Option
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5.1.2 Option B: SX1261 with LDO Regulator
The LDO Regulator is used, for both the core of the
chip and the PA.
Advantage of this option:
VDD_IN
The cost and space for the external 15 H and 47 nH
inductors are spared.
SX1261
Main supply
1.8 to 3.7 V
Figure 5-2: SX1261 Diagram with the LDO Regulator Power Option
5.1.3 Option C: SX1262 with DC-DC Regulator
The DC-DC Regulator is used with about 90% of
efficiency, for the chip core only. The PA regulator is
supplied with VBAT.
VDD_IN
Advantage of this option:
The power consumption of the core is reduced.
SX1262
Main supply
1.8* to 3.7 V
*VBAT=3.3 V min. to reach +22 dBm
Figure 5-3: SX1262 Diagram with the DC-DC Regulator Power Option
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5.1.4 Option D: SX1262 with LDO Regulator
The LDO Regulator is used. Power consumption of
the core is slightly higher than in Option C.
Advantage of this option:
VDD_IN
The cost and space for an external 15 H inductor
are spared.
SX1262
Main supply
1.8* to 3.7 V
* VBAT=3.3 V min. to reach +22 dBm
Figure 5-4: SX1262 Diagram with the LDO Regulator Power Option
5.1.5 Consideration on the DC-DC Inductor Selection
The selection of the inductor is essential to ensure optimal performance of the DC-DC internal block. Selecting an incorrect
inductor could cause various unwanted effects ranging from ripple currents to early aging of the device, as well as a
degradation of the efficiency of the DC-DC regulator.
For the SX1261/2, the preferred inductor will be shielded, presenting a low internal series resistance and a resonance
frequency much higher than the DC-DC switching frequency. When selecting the 15 μH inductor, the user should therefore
select a part with the following considerations:
•
•
•
DCR (max) = 2 ohms
Idc (min) = 100 mA
Freq (min) = 20 MHz
Table 5-3: Typical 15 μH Inductors
Value
(μH)
Idc max
(mA)
Freq
(MHz)
DCR
(ohm)
Package
(L x W x H in mm)
Reference
Manufacturer
LPS3010-153
MLZ2012N150L
MLZ2012M150W
VLS2010ET-150M
VLS2012ET-150M
Coilcraft
TDK
15
15
15
15
15
370
90
43
40
40
40
40
0.95
0.47
2.95 x 2.95 x 0.9
2 x 1.25 x 1.25
2 x 1.25 x 1.25
2 x 2 x 1
TDK
120
440
440
0.95
TDK
1.476
1.062
TDK
2 x 2 x 1.2
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5.2 Flexible DIO Supply
The transceiver has two power supply pins, one for the core of the transceiver called VBAT and one for the host controller
interface (SPI, DIOs, BUSY) called VBAT_IO. Both power supplies can be connected together in application. In case a low
voltage micro-controller (typically with IO pads at 1.8 V) is used to control the transceiver, the user can:
•
•
•
use VBAT at 3.3 V for optimal RF performance
directly connect VBAT_IO to the same supply used for the micro-controller
connect the digital IOs directly to the micro-controller DIOs.
At any time, VBAT_IO must be lower than or equal to VBAT.
Regulator 1.8 V
VBAT_IO
VBAT
Battery
Typ. 1.8 to 3.7 V
Controller
Transceiver
SPI
DIOx
NRESET
Requirement: VBAT ≥ VBAT_IO
Figure 5-5: Separate DIO Supply
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6. Modems
The SX1261/2 contains different modems capable of handling LoRa® and FSK modulations. LoRa® and FSK are associated
with their own frame and modem.
•
•
LoRa® modem LoRa® Frame
FSK modem FSK Frame
The user specifies the modem and frame type by using the command SetPacketType(...). This command specifies the frame
used and consequently the modem implemented.
This function is the first one to be called before going to Rx or Tx and before defining modulation and packet parameters.
The command GetPacketType() returns the current protocol of the radio.
6.1 LoRa® Modem
The LoRa® modem uses spread spectrum modulation and forward error correction techniques to increase the range and
robustness of radio communication links compared to traditional FSK based modulation.
An important facet of the LoRa® modem is its increased immunity to interference. The LoRa® modem is capable of
co-channel GMSK rejection of up to 19 dB. This immunity to interference permits the simple coexistence of LoRa®
modulated systems either in bands of heavy spectral usage or in hybrid communication networks that use LoRa® to extend
range when legacy modulation schemes fail.
6.1.1 Modulation Parameter
It is possible to optimize the LoRa® modulation for a given application, access is given to the designer to four critical design
parameters, each one permitting a trade-off between the link budget, immunity to interference, spectral occupancy and
nominal data rate. These parameters are:
•
•
•
•
Modulation BandWidth (BW_L)
Spreading Factor (SF)
Coding Rate (CR)
Low Data Rate Optimization (LDRO)
These parameters are set using the command SetModulationParams(...) which must be called after defining the protocol.
6.1.1.1 Spreading Factor
The spread spectrum LoRa® modulation is performed by representing each bit of payload information by multiple chips of
information. The rate at which the spread information is sent is referred to as the symbol rate (Rs), the ratio between the
nominal symbol rate and chip rate is the spreading factor and it represents the number of symbols sent per bit of
information.
Consideration on SF5 and SF6
In the SX1261/2, two new spreading factors have been added compared to the previous device family: the SF5 and the SF6.
These two new spreading factors have been modified slightly for the SX1261/2 and will now be able to operate in both
implicit and explicit mode. However, these modification have made the new spreading factor incompatible with previous
device generation. Especially, the SF6 on the SX1261/2 will not be backward compatible with the SF6 used on the SX1276.
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Furthermore, due to the higher symbol rate, the minimum recommended preamble length needed to ensure correct
detection and demodulation from the receiver is increased compared to other Spreading Factors. For SF5 and SF6, the user
is invited to use 12 symbols of preamble to have optimal performances over the dynamic range or the receiver.
Note:
The spreading factor must be known in advance on both transmit and receive sides of the link as different spreading factors
are orthogonal to each other. Note also the resulting Signal to Noise Ratio (SNR) required at the receiver input.
It is the capability to receive signals with negative SNR that increases the sensitivity as well as link budget and range of the
LoRa® receiver.
Table 6-1: Range of Spreading Factors (SF)
Spreading Factor (SF)
5
6
7
8
9
10
11
12
2^SF (Chips / Symbol)
32
64
-5
128
-7.5
256
-10
512
1024
-15
2048
-17.5
4096
-20
Typical LoRa® Demodulator SNR [dB]
-2.5
-12.5
A higher spreading factor provides better receiver sensitivity at the expense of longer transmission times (time-on-air).
6.1.1.2 Bandwidth
An increase in signal bandwidth permits the use of a higher effective data rate, thus reducing transmission time at the
expense of reduced sensitivity improvement.
LoRa® modem operates at a programmable bandwidth (BW_L) around a programmable central frequency f
RF
BW_L
f
BWL
2
BWL
2
fRF
f
RF – ------------
f
RF + ------------
Figure 6-1: LoRa® Signal Bandwidth
An increase in LoRa® signal bandwidth (BW_L) permits the use of a higher effective data rate, thus reducing transmission
time at the expense of reduced sensitivity improvement. There are regulatory constraints in most countries on the
permissible occupied bandwidth. The LoRa® modem bandwidth always refers to the double side band (DSB). The range of
LoRa® signal bandwidths available is given in the table below:
Table 6-2: Signal Bandwidth Setting in LoRa® Mode
Signal Bandwidth
0
1
2
3
4
5
6
7
8
9
BW_L [kHz] 0
7.810
10.420
15.630
20.830
31.250
41.670
62.50
1250
250 1
500 1
1. For RF frequencies below 400 MHz, there is a scaling between the frequency and supported BW, some BW may not be available below 400 MHz
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For BW_L up to 250 kHz, the receiver performs a double conversion. A first down conversion to low- IF is performed inside
the RF chain, a second conversion to baseband is performed digitally inside the baseband modem. When the 500 kHz
bandwidth is used, a single down-conversion to zero-IF is performed in the RF part.
6.1.1.3 FEC Coding Rate
To further improve the robustness of the link the LoRa® modem employs cyclic error coding to perform forward error
detection and correction.
Forward Error Correction (FEC) is particularly efficient in improving the reliability of the link in the presence of interference.
So that the coding rate and robustness to interference can be changed in response to channel conditions. The coding rate
selected on the transmitter side is communicated to the receiver through the header (when present).
Table 6-3: Coding Rate Overhead
Cyclic Coding Rate CR
[in raw bits / total bits]
Coding Rate
Overhead Ratio
1
2
3
4
4/5
4/6
4/7
4/8
1.25
1.5
1.75
2
A higher coding rate provides better noise immunity at the expense of longer transmission time. In normal conditions a
factor of 4/5 provides the best trade-off; in the presence of strong interferers a higher coding rate may be used. Error
correction code does not have to be known in advance by the receiver since it is encoded in the header part of the packet.
6.1.1.4 Low Data Rate Optimization
For low data rates (typically for high SF or low BW) and very long payloads which may last several seconds in the air, the low
data rate optimization (LDRO) can be enabled. This reduces the number of bits per symbol to the given SF minus two (see
Section 6.1.4 "LoRa® Time-on-Air" on page 41) in order to allow the receiver to have a better tracking of the LoRa® signal.
Depending on the payload size, the low data rate optimization is usually recommended when a LoRa® symbol time is equal
or above 16.38 ms.
6.1.1.5 LoRa® Transmission Parameter Relationship
With a knowledge of the key parameters that can be selected by the user, the LoRa® symbol rate is defined as:
BW
Rs = ---------
SF
2
where BW is the programmed bandwidth and SF is the spreading factor. The transmitted signal is a constant envelope
signal. Equivalently, one chip is sent per second per Hz of bandwidth.
6.1.2 LoRa® Packet Engine
LoRa® has it own packet engine that supports the LoRa® PHY as described in the following section.
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6.1.3 LoRa® Frame
The LoRa® modem employs two types of packet formats: explicit and implicit. The explicit packet includes a short header
that contains information about the number of bytes, coding rate and whether a CRC is used in the packet. The packet
format is shown in the following figure.
Figure 6-2: LoRa® Packet Format
The LoRa® packet starts with a preamble sequence which is used to synchronize the receiver with the incoming signal. By
default the packet is configured with a 12-symbol long sequence. This is a programmable variable so the preamble length
may be extended; for example, in the interest of reducing the receiver duty cycle in receive intensive applications. The
transmitted preamble length may vary from 10 to 65535 symbols, once the fixed overhead of the preamble data is
considered. This permits the transmission of near arbitrarily long preamble sequences.
The receiver undertakes a preamble detection process that periodically restarts. For this reason the preamble length should
be configured as identical to the transmitter preamble length. Where the preamble length is not known, or can vary, the
maximum preamble length should be programmed on the receiver side.
The preamble is followed by a header which contain information about the following payload. The packet payload is a
variable-length field that contains the actual data coded at the error rate either as specified in the header in explicit mode
or as selected by the user in implicit mode. An optional CRC may be appended.
Depending upon the chosen mode of operation two types of header are available.
6.1.3.1 Explicit Header Mode
This is the default mode of operation. Here the header provides information on the payload, namely:
•
•
•
The payload length in bytes
The forward error correction coding rate
The presence of an optional 16-bit CRC for the payload
The header is transmitted with maximum error correction code (4/8). It also has its own CRC to allow the receiver to discard
invalid headers.
6.1.3.2 Implicit Header Mode
In certain scenarios, where the payload, coding rate and CRC presence are fixed or known in advance, it may be
advantageous to reduce transmission time by invoking implicit header mode. In this mode the header is removed from the
packet. In this case the payload length, error coding rate and presence of the payload CRC must be manually configured
identically on both sides of the radio link.
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6.1.4 LoRa® Time-on-Air
The packet format for the LoRa® modem is detailed in Figure 6-3: Fixed-Length Packet Format and Figure 6-4:
Variable-Length Packet Format. The equation to obtain Time On Air (ToA) is:
with:
•
•
•
•
SF: Spreading Factor (5 to 12)
BW: Bandwidth (in kHz)
ToA: the Time on Air in ms
N
: number of symbols
symbol
The computation of the number of symbols differs depending on the parameters of the modulation.
For SF5 and SF6:
For all other SF:
For all other SF with Low Data Rate Optimization activated:
With:
•
•
•
N_bit_CRC = 16 if CRC activated, 0 if not
N_symbol_header = 20 with explicit header, 0 with implicit header
CR is 1, 2, 3 or 4 for respective coding rates 4/5, 4/6, 4/7 or 4/8
6.1.5 LoRa® Channel Activity Detection (CAD)
The use of a spread spectrum modulation technique presents challenges in determining whether the channel is already in
use by a signal that may be below the noise floor of the receiver. The use of the RSSI in this situation would clearly be
impracticable. To this end the channel activity detector is used to detect the presence of other LoRa® signals.
On the SX1261/2, the channel activity detection mode is designed to detect the presence of a LoRa® preamble or data
symbols while the previous generations of products were only able to detect LoRa® preamble symbols.
Once in CAD mode, the SX1261/2 will perform a scan of the band for a user-selectable duration (defined in number of
symbols) and will then return with the Channel Activity Detected IRQ if LoRa® symbols have been detected during the CAD.
The time taken for the channel activity detection is dependent upon the LoRa® modulation settings used. For a given
configuration (SF/BW) the typical CAD detection time can be selected to be either 1, 2, 4, 8 or 16 symbols. Once the duration
of the selected number of symbols has been done, the radio will remains for around half a symbol in Rx to post-process the
measurement.
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6.2 FSK Modem
6.2.1 Modulation Parameter
The FSK modem is able to perform transmission and reception of 2-FSK modulated packets over a range of data rates
ranging from 0.6 kbps to 300 kbps. All parameters are set by using the command SetModulationParams(...). This function
should be called only after defining the protocol.
The bitrate setting is referenced to the crystal oscillator and provides a precise means of setting the bit rate (or equivalently
chip) rate of the radio. In the command SetModulationParams(...), the bitrate is expressed as 32 times the XTAL frequency
divided the real bit rate used by the device. The generic formula is:
F
XOSC
BR = -------------------*32
BitRate
FSK modulation is performed inside the PLL bandwidth, by changing the fractional divider ratio in the feedback loop of the
PLL. The high resolution of the sigma-delta modulator, allows for very narrow frequency deviation. The frequency deviation
Fdev is one of the parameters of the function SetModulationParams(...) and is expressed as:
FdevHz
Fdev = -----------------------
FreqStep
where:
XtalFreq
FreqStep = -----------------------
25
2
Additionally, in transmission mode, several shaping filters can be applied to the signal in packet mode or in continuous
mode. In reception mode, the user needs to select the best reception bandwidth depending on its conditions. To ensure
correct demodulation, the following limit must be respected for the selection of the bandwidth:
2*Fdev + BR < BW
The bandwidth is defined by parameter BW as described in the following table.
Table 6-4: Bandwidth Definition in FSK Packet Type
BW
Value
Bandwidth [kHz DSB]
BW4
BW5
0x1F
0x17
0x0F
0x1E
0x16
0x0E
0x1D
0x15
0x0D
4.8
5.8
BW7
7.3
BW9
9.7
BW11
BW14
BW19
BW23
BW29
11.7
14.6
19.5
23.4
29.3
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Table 6-4: Bandwidth Definition in FSK Packet Type
BW
Value
Bandwidth [kHz DSB]
BW39
BW46
0x1C
0x14
0x0C
0x1B
0x13
0x0B
0x1A
0x12
0x0A
0x19
0x11
0x09
39.0
46.9
BW58
58.6
BW78
78.2
BW93
93.8
BW117
BW156
BW187
BW234
BW312
BW373
BW467
117.3
156.2
187.2
234.3
312.0
373.6
467.0
The bandwidth must be chosen so that
Bandwidth[DSB] ≥ BR + 2*frequency deviation + frequency error
where the frequency error is two times the crystal frequency error used.
The SX1261/2 offers several pulse shaping options defined by the parameter PulseShape. If other unspecified values are
given as parameters, then no filtering is used.
6.2.2 FSK Packet Engine
The SX1261/2 is designed for packet-based transmission. The packet controller block is responsible for assembly of
received data bit-stream into packets and their storage into the data buffer. It also performs the bit-stream decoding
operations such as de-whitening & CRC-checks on the received bit-stream.
On the transmit side, the packet handler can construct a packet and send it bit by bit to the modulator for transmission. It
can whiten the payload and append the CRC-checksum to the end of the packet. The packet controller only works in
half-duplex mode i.e. either in transmit or receive at a time.
The packet controller is configured using the command SetPacketParams(...) as in Section 13.4.6 "SetPacketParams" on
page 87. This function can be called only after defining the protocol. The next chapters describe in detail the different
frames available in the SX1261/2.
6.2.2.1 Preamble Detection in Receiver Mode
The SX1261/2 is able to gate the reception of a packet if an insufficient number of alternating preamble symbols (usually
referred to 0x55 or 0xAA in hexadecimal form) has been detected. This can be selected by the user by using the parameter
PreambleDetectorLength used in the command SetPacketParams(...). The user can select a value ranging from “Preamble
detector length off” - where the radio will not perform any gating and will try to lock directly on the following Sync Word -
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to “Preamble detector length 32 bits” where the radio will be expecting to receive 32 bits of preamble before the following
Sync Word. In this case, if the 32 bits of preamble are not detected, the radio will either drop the reception in RxSingle mode,
or restart its tracking loop in RxContinuous mode.
To achieve best performance of the device, it is recommended to set PreambleDetectorLength to “Preamble detector length
8 bits” or “Preamble detector length 16 bits” depending of the complete size of preamble which is sent by the transmitter.
Note: In all cases, PreambleDetectorLength must be smaller than the size of the following Sync Word to achieve proper
detection of the packets. If the preamble length is greater than the following Sync Word length (typically when no Sync
Word is used) the user should fill some of the Sync Word bytes with 0x55.
6.2.3 FSK Packet Format
The FSK packet format provides a conventional packet format for application in proprietary NRZ coded, low energy
communication links. The packet format has built in facilities for CRC checking of the payload, dynamic payload size and
packet acknowledgement. Optionally whitening based upon pseudo random number generation can be enabled. Two
principle packet formats are available in the FSK protocol: fixed length and variable length packets.
6.2.3.1 Fixed-Length Packet
If the packet length is fixed and known on both sides of the link then knowledge of the packet length does not need to be
transmitted over the air. Instead the packet length can be written to the parameter packetLength which determines the
packet length in bytes (0 to 255).
Preamble
8 to 65535
bits
Sync Word Address
0 to 8 bytes 0 to 1 byte
Payload
1 to 255 bytes
CRC
0, 1 or 2 bytes
CRC Checksum
Whitening
Figure 6-3: Fixed-Length Packet Format
The preamble length is set from 8 to 65535 bits using the parameter PreambleLen. It is usually recommended to use a
minimum of 16 bits for the preamble to guarantee a valid reception of the packet on the receiver side. The CRC
operation, packet length and preamble length are defined using the command SetPacketParams(...) as defined in
Section 11. "List of Commands" on page 61.
6.2.3.2 Variable-Length Packet
Where the packet is of uncertain or variable size, then information about the packet length must be transmitted within the
packet. The format of the variable-length packet is shown below.
Preamble
8 to 65535
bits
Address
0 to 1
byte
Sync Word
0 to 8 bytes
Length
1 byte
Payload
0 to 255 bytes
CRC
0, 1 or 2 bytes
CRC Checksum
Whitening
Figure 6-4: Variable-Length Packet Format
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6.2.3.3 Setting the Packet Length or Node Address
The packet length and Node or Broadcast address are not considered part of the payload and they are added automatically
in hardware.
The packet length is added automatically in the packet when the packetType field is set to variable size in the command
SetPacketParam(...).
The node or broadcast address can be enabled by using the AddrComp field is in the command SetPacketParam(...). This
field allow the user to enable and select an additional packet filtering at the payload level.
6.2.3.4 Whitening
The whitening process is built around a 9-bit LFSR which is used to generate a random sequence and the payload (including
the payload length, the Node or Broadcase address and CRC checksum when needed) is then XORed with this random
sequence to generate the whitened payload. The data is de-whitened on the receiver side by XORing with the same
random sequence. This setup limits the number of consecutive 1’s or 0’s to 9. Note that the data whitening is only required
when the user data has high correlation with long strings of 0’s and 1’s. If the data is already random then the whitening is
not required. For example a random source generating the Transmit data, when whitened, could produce longer strings of
1’s and 0’s, thus it’s not required to randomize an already random sequence.
LFSR Polynom ial =X9 + X5 + 1
X8
X7
X6
X5
X4
X3
X2
X1
X0
W hitened data
Transmit data
Figure 6-5: Data Whitening LFSR
The whitening is based around the 9-bit LFSR polynomial x^9+x^5+1. With this structure, the LSB at the output of the LFSR
is XORed with the MSB of the data.
At the initial stage, each flip-flop of the LFSR can be initialized through the registers at addresses 0x06B8 and 0x6B9.
Table 6-5: Whitening Initial Value
Whitening Initial Value
Register Address
Default Value
Whitening initial value MSB
Whitening initial value LSB
0x06B8
0x06B9
0x01
0x00
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6.2.3.5 CRC
The SX1261/2 offers full flexibility to select the polynomial and initial value of the selected polynomial. In additions, the user
can also select a complete inversion of the computed CRC to comply with some international standards.
The CRC can be enabled and configured by using the CRCType field in the command SetPacketParam(...). This field allows
the user to enable and select the length and configuration of the CRC.
Table 6-6: CRC Type Configuration
CRCType
Description
0x01
0x00
0x02
0x04
0x06
CRC_OFF (No CRC)
CRC_1_BYTE (CRC computed on 1 byte)
CRC_2_BYTE (CRC computed on 2 bytes)
CRC_1_BYTE_INV (CRC computed on 1 byte and inverted)
CRC_2_BYTE_INV (CRC computed on 2 bytes and inverted)
The CRC selected must be modified together with the CRC initial value and CRC polynomial.
Table 6-7: CRC Initial Value
Register Address
Default Value
CRC MSB Initial Value [15:8]
CRC LSB Initial Value [7:0]
0x06BC
0x06BD
0x1D
0x0F
Table 6-8: CRC Polynomial
Register Address
Default Value
CRC MSB Polynomial Value [15:8]
CRC LSB Polynomial Value [7:0]
0x06BE
0x06BF
0x10
0x21
This flexibility permits the user to select any standard CRC or to use his own CRC allowing a specific detection of a given
packet. Examples:
To use the IBM CRC configuration, the user must select:
•
•
•
0x8005 for the CRC polynomial
0xFFFF for the initial value
CRC_2_BYTE for the field CRCType in the command SetPacketParam(...).
For the CCIT CRC configuration the user must select:
•
•
•
0x1021 for the CRC polynomial
0x1D0F for the initial value
CRC_2_BYTE_INV for the field CRCType in the command SetPacketParam(...)
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7. Data Buffer
The transceiver is equipped with a 256-byte RAM data buffer which is accessible in all modes except sleep mode. This RAM
area is fully customizable by the user and allows access to either data for transmission or from the last packet reception.
7.1 Principle of Operation
0xFF
USER
TRANSCEIVER
txBaseAddress + txPayloadLength
TxBufferPointer
Transmitted
Payload
WriteBuffer()
SetBufferBaseAddress()
rxBaseAddress + rxPayloadLength
GetRxBufferStatus()
Received
Payload
RxStartBufferPointer
SetBufferBaseAddress()
0x00
Data buffer
Capacity = 256 bytes
Figure 7-1: Data Buffer Diagram
The data buffer can be configured to store both transmit and receive payloads.
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7.2 Data Buffer in Receive Mode
In receive mode RxBaseAddr specifies the buffer offset in memory at which the received packet payload data will be written.
The buffer offset of the last byte written in receive mode is then stored in RxDataPointer which is initialized to the value of
RxBaseAddr at the beginning of the reception.
The pointer to the first byte of the last packet received and the packet length can be read with the command
GetRxbufferStatus().
In single mode, RxDataPointer is automatically initialized to RxBaseAddr each time the transceiver enters Rx mode. In
continuous mode the pointer is incremented starting from the previous position.
7.3 Data Buffer in Transmit Mode
Upon each transition to transmit mode TxDataPointer is initialized to TxBaseAddr and is incremented each time a byte is sent
over the air. This operation stops once the number of bytes sent equals the payloadlength parameter as defined in the
function SetPacketParams(...).
7.4 Using the Data Buffer
Both, RxBaseAddr and TxBaseAddr are set using the command SetBufferBaseAddresses(...).
By default RxBaseAddr and TxBaseAddr are initialized at address 0x00.
Due to the contiguous nature of the data buffer, the base addresses for Tx and Rx are fully configurable across the 256-byte
memory area. Each pointer can be set independently anywhere within the buffer. To exploit the maximum data buffer size
in transmit or receive mode, the whole data buffer can be used in each mode by setting the base addresses TxBaseAddr and
RxBaseAddr at the bottom of the memory (0x00).
The data buffer is cleared when the device is put into Sleep mode (implying no access). The data is retained in all other
modes of operation.
The data buffer is acceded via the command WriteBuffer(...) and ReadBuffer(...). In this function the parameter offset defines
the address pointer of the first data to be written or read. Offset zero defines the first position of the data buffer.
Before any read or write operation it is hence necessary to initialize this offset to the corresponding beginning of the buffer.
Upon reading or writing to the data buffer the address pointer will then increment automatically.
Two possibilities exist to obtain the offset value:
•
•
First is to use the RxBaseAddr value since the user defines it before receiving a payload.
Second, offset can be initialized with the value of RxStartBufferPointer returned by GetRxbufferStatus(...) command.
Note:
All the received data will be written to the data buffer even if the CRC is invalid, permitting user-defined post processing of
corrupted data. When receiving, if the packet size exceeds the buffer memory allocated for the Rx, it will overwrite the
transmit portion of the data buffer.
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8. Digital Interface and Control
The SX1261/2 is controlled via a serial SPI interface and a set of general purpose input/output (DIOs). At least one DIO must
be used for IRQ and the BUSY line is mandatory to ensure the host controller is ready to accept the commands. The
SX1261/2 uses an internal controller (CPU) to handle communication and chip control (mode switching, API etc...). BUSY is
used as a busy signal indicating that the chip is ready for new command only if this signal is low. When BUSY is high, the
host controller must wait until it goes down again before sending another command. Through SPI the application sends
commands to the internal chip or access directly the data memory space.
8.1 Reset
A complete “factory reset” of the chip can be issued on request by toggling pin 15 NRESET of the SX1261/2. It will be
automatically followed by the standard calibration procedure and any previous context will be lost. The pin should be held
low for more than 50 μs (typically 100 μs) for the Reset to happen.
8.2 SPI Interface
The SPI interface gives access to the configuration register via a synchronous full-duplex protocol corresponding to CPOL
= 0 and CPHA = 0 in Motorola/Freescale nomenclature. Only the slave side is implemented.
An address byte followed by a data byte is sent for a write access whereas an address byte is sent and a read byte is received
for the read access. The NSS pin goes low at the beginning of the frame and goes high after the data byte.
MOSI is generated by the master on the falling edge of SCK and is sampled by the slave (i.e. this SPI interface) on the rising
edge of SCK. MISO is generated by the slave on the falling edge of SCK.
A transfer is always started by the NSS pin going low. MISO is high impedance when NSS is high.
The SPI runs on the external SCK clock to allow high speed up to 16 MHz.
8.2.1 SPI Timing When the Transceiver is in Active Mode
In this mode the chip is able to handle SPI command in a standard way i.e. no extra delay needed at the first SPI transaction.
Figure 8-1: SPI Timing Diagram
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All timings in following table are given for a max load cap of 10 pF.
Table 8-1: SPI Timing Requirements
Symbol
Description
Minimum
Typical
Maximum
Unit
t1
t2
t3
t4
t5
t6
t7
t8
t9
NSS falling edge to SCK setup time
SCK period
32
62.5
31.25
5
-
-
-
-
-
-
-
-
-
-
-
ns
ns
ns
ns
ns
ns
ns
ns
ns
SCK high time
-
MOSI to SCK hold time
MOSI to SCK setup time
NSS falling to MISO delay
SCK falling to MISO delay,
SCK to NSS rising edge hold time
NSS high time
-
5
-
0
15
15
-
0
31.25
125
-
NSS falling edge to SCK setup time when switching
from SLEEP to STDBY_RC mode
t10
t11
100
0
-
-
-
s
s
NSS falling to MISO delay when switching from
SLEEP to STDBY_RC mode
150
8.2.2 SPI Timing When the Transceiver Leaves Sleep Mode
One way for the chip to leave Sleep mode is to wait for a falling edge of NSS. At falling edge, all necessary internal regulators
are switched On; the chip starts chip initialization before being able to accept first SPI command. This means that the delay
between the falling edge of NSS and the first rising edge of SCK must take into account the wake-up sequence and the chip
initialization. In Sleep mode and during the initialization phase, the busy signal mapped on BUSY pin, is set high indicating
to the host that the chip is not able to accept a new command. Once the chip is in STDBY_RC mode, the busy signal goes
low and the host can start sending a command. This is also true for startup at battery insertion or after a hard reset.
Figure 8-2: SPI Timing Transition
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8.3 Multi-Purpose Digital Input/Output (DIO)
The chip is interfaced through the 4 control lines which are composed of the BUSY pin and 3 DIOs pins that can be
configured as interrupt, debug or to control the radio immediate peripherals (TCXO or RF Switch).
8.3.1 BUSY Control Line
The BUSY control line is used to indicate the status of the internal state machine. When the BUSY line is held low, it indicates
that the internal state machine is in idle mode and that the radio is ready to accept a command from the host controller.
The BUSY control line is set back to zero once the chip has reached a stable mode and it is ready for a new command.
Inherently, the amount of time the BUSY line will stay high depends on the nature of the command. For example, setting
the device into TX mode from the STDBY_RC mode will take much more time than simply changing some radio parameters
because the internal state machine will maintain the BUSY line high until the radio is effectively transmitting the packet.
BUSY
NSS
SPI
opcode
Param…
Param1
(MOSI, MISO, SCK)
Figure 8-3: Switching Time Definition
From the internal state machine point of view, all “write” command will make the BUSY line to go high after a small lap of
time represented as T on the graph above. T represents the time needed by the internal state machine to wake-up and
SW
SW
start processing the command.
Conversely, the “read” command will be handled directly without the help of the internal state machine and thus the BUSY
line will remains low after a “read” command.
The max value for T from NSS rising edge to the BUSY rising edge is, in all cases, 600 ns.
SW
In Sleep mode, the BUSY pin is held high through a 20 kΩ resistor and the BUSY line will go low as soon as the radio leaves
the Sleep mode.
In FS, BUSY will go low when the PLL is locked.
In RX, BUSY will go to low as soon as the RX is up and ready to receive data.
In TX, BUSY will go low when the PA has ramped-up and transmission of preamble starts.
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In additon to this, the BUSY will also go high to handle its internal IRQ. In this scenario, it is essential to wait for the BUSY
line to go low before sending an SPI command (either a “read” or “write” command).
BUSY
NSS
SPI
opcode
Param…
Param1
(MOSI, MISO, SCK)
ࢀ
࢙
࢝
Mode
Figure 8-4: Switching Time Definition in Active Mode
The following table gives the value of T Mode for all possible transitions. The switching time is defined as the time
SW
between the rising edge of the NSS ending the SPI transaction and the falling edge of BUSY.
Table 8-2: Switching Time
Transition
T
Mode Typical Value [s]
SW
SLEEP to STBY_RC cold start (no data retention)
3500
340
31
SLEEP to STBY_RC warm start (with data retention)
STBY_RC to STBY_XOSC
STBY_RC to FS
STBY_RC to RX
STBY_RC to TX
STBY_XOSC to FS
STBY_XOSC to TX
STBY_XOSC to RX
FS to RX
50
83
126
40
105
62
41
FS to TX
76
RX to FS
15
RX to TX
92
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8.3.2 Digital Input/Output
Any of the 3 DIOs can be selected as an output interrupt source for the application. When the application receives an
interrupt, it can determine the source by using the command GetIrqStatus(...). The interrupt can then be cleared using the
ClearIrqStatus(...) command. The Pin Description is as follows:
DIO1 is the generic IRQ line, any interrupt can be mapped to DIO1. The complete list of available IRQ can be found in
Section 8.4 "Digital Interface Status versus Chip modes" on page 53.
DIO2 has a double functionality. As DIO1, DIO2 can be used as a generic IRQ line and any IRQ can be routed through this
pin. Also, DIO2 can be configured to drive an RF switch through the use of the command SetDio2AsRfSwitchCtrl(...). In this
mode, DIO2 will be at a logical 1 during Tx and at a logical 0 in any other mode.
DIO3 also has a double functionality and as DIO1 or DIO2, it can be used as a generic IRQ line. Also, DIO3 can be used to
automatically control a TCXO through the command SetDio3AsTCXOCtrl(...). In this case, the device will automatically power
cycle the TCXO when needed.
8.4 Digital Interface Status versus Chip modes
Table 8-3: Digital Pads Configuration for each Chip Mode
Mode
DIO3
DIO2
DIO1
BUSY
MISO
MOSI
SCK
NSS
NRESET
Reset
Start-up
Sleep
PD
HIZ PD
HIZ PD
OUT
PD
HIZ PD
HIZ PD
OUT
PD
HIZ PD
HIZ PD
OUT
PU
HIZ PU
HIZ PU
OUT
HIZ
HIZ
HIZ
HIZ
HIZ
IN
HIZ
HIZ
HIZ
IN
IN
IN
IN
IN
IN
IN
IN
IN
-
IN PU
IN PU
IN PU
IN PU
IN PU
IN PU
IN PU
HIZ
STBY_RC
STBY_XOSC
FS
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
IN
IN
OUT
OUT
OUT
OUT
IN
IN
RX
OUT
OUT
OUT
OUT
IN
IN
TX
OUT
OUT
OUT
OUT
IN
IN
Note:
•
•
PU = pull up with 50 kat typical conditions
PD = pull down with 50 k at typical conditions (the resistor value varies with the supply voltage)
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8.5 IRQ Handling
In total there are 10 possible interrupt sources depending on the selected frame and chip mode. Each one can be enabled
or masked. In addition, each one can be mapped to DIO1, DIO2 or DIO3.
Table 8-4: IRQ Status Registers
Bit
0
IRQ
TxDone
Description
Packet transmission completed
Packet received
Protocol
All
1
RxDone
All
2
PreambleDetected
SyncWordValid
HeaderValid
HeaderErr
Preamble detected
All
3
Valid Sync Word detected
Valid LoRa Header received
LoRa® header CRC error
FSK
4
LoRa®
5
LoRa®
All
6
7
CrcErr
Wrong CRC received
CadDone
Channel activity detection finished
LoRa®
8
9
CadDetected
Timeout
Channel activity detected
Rx or Tx Timeout
LoRa®
All
For more information on how to setup IRQ and DIOs, refer to the function SetDioIrqParams() in Section 13.3.1
"SetDioIrqParams" on page 78.
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9. Operational Modes
The SX1261/2 features six operating modes. The analog front-end and digital blocks that are enabled in each operating
mode are explained in the following table.
Table 9-1: SX1261/2 Operating Modes
Mode
Enabled Blocks
SLEEP
Optional registers, backup regulator, RC64k oscillator, data RAM
Top regulator (LDO), RC13M oscillator
STDBY_RC
STDBY_XOSC
Top regulator (DC-DC or LDO), XOSC
FS
Tx
Rx
All of the above + Frequency synthesizer at Tx frequency
Frequency synthesizer and transmitter, Modem
Frequency synthesizer and receiver, Modem
9.1 Startup
At power-up or after a reset, the chip goes into STARTUP state, the control of the chip being done by the sleep state
machine operating at the battery voltage. The BUSY pin is set to high indicating that the chip is busy and cannot accept a
command. When the digital voltage and RC clock become available, the chip can boot up and the CPU takes control. At this
stage the BUSY line goes down and the device is ready to accept commands.
9.2 Calibrate
Calibration procedure is automatically called in case of POR or via the calibration command. Parameters can be added to
the calibrate command to identify which section of calibration should be repeated. The following blocks can be calibrated:
•
•
•
•
•
RC64k using the 32 MHz crystal oscillator as reference
RC13M using the 32 MHz crystal oscillator as reference
PLL to select the proper VCO frequency and division ratio for any RF frequency
RX ADC
Image (RX mode with defined tone)
Once the calibration is finished, the chip enters STDBY_RC mode.
9.2.1 Image Calibration for Specific Frequency Bands
The image calibration is done through the command CalibrateImage(...) for a given range of frequencies defined by the
parameters freq1 and freq2. Once performed, the calibration is valid for all frequencies between the two extremes used as
parameters. Typically, the user can select the parameters freq1 and freq2 to cover any specific ISM band.
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Table 9-2: Image Calibration Over the ISM Bands
Frequency Band [MHz]
Freq1
Freq2
430 - 440
470 - 510
779 - 787
863 - 870
902 - 928
0x6B
0x75
0x6F
0x81
0xC1
0xC5
0xD7
0xDB
0xE1 (default)
0xE9 (default)
In case of POR or when the device is recovering from Sleep mode in cold start mode, the image calibration is performed as
part of the initial calibration process and for optimal image rejection in the band 902 - 928 MHz. However at this stage the
internal state machine has no information whether an XTAL or a TCXO is fitted. When the 32 MHz clock is coming from a
TCXO, the calibration will fail and the user should request a complete calibration after calling the function
SetDIO3AsTcxoCtrl(...).
By default, the image calibration is made in the band 902 - 928 MHz. Nevertheless, it is possible to request the device to
perform a new image calibration at other frequencies.
Note:
Contact your Semtech representative for the other optimal calibration settings outside of the given frequency bands.
9.3 Sleep Mode
In this mode, most of the radio internal blocks are powered down or in low power mode and optionally the RC64k clock
and the timer are running. The chip may enter this mode from STDBY_RC and can leave the SLEEP mode if one of the
following events occurs:
•
•
NSS pin goes low in any case
RTC timer generates an End-Of-Count (corresponding to Listen mode)
When the radio is in Sleep mode, the BUSY pin is held high.
9.4 Standby (STDBY) Mode
In standby mode the host should configure the chip before going to RX or TX modes. By default in this state, the system is
clocked by the 13 MHz RC oscillator to reduce power consumption (in all other modes except SLEEP the XTAL is turned ON).
However if the application is time critical, the XOSC block can be turned or left ON.
XOSC or RC13M selection in standby mode is determined by mode parameter in the command SetStandby(...).
The mode where only RC13M is used is called STDBY_RC and the one with XOSC ON is called STDBY_XOSC.
If DC-DC is to be used, the selection should be made while the circuit is in STDBY_RC mode by using the
SetRegulatorMode(...) command, then the DC-DC will automatically switch ON when entering STDBY_XOSC mode. The
DC-DC will be clocked by the RC13M. The LDO will remain active with a target voltage 50 mV lower than the DC-DC one.
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9.5 Frequency Synthesis (FS) Mode
In FS mode, PLL and related regulators are switched ON. The BUSY goes low as soon as the PLL is locked or timed out.
For debugging purposes the chip may be requested to remain in this mode by using the SetFs() command.
Since the SX1261/2 uses low IF architecture, the RX and TX frequencies are different. The RX frequency is equal to TX one
minus the intermediate frequency (IF). In FS or TX modes, the RF frequency is directly programmed by the user.
9.6 Receive (RX) Mode
In RX mode, the RF front-end, RX ADC and the selected modem (LoRa® or FSK) are turned ON. In RX mode the circuit can
operate in different sub-modes:
•
Continuous mode: the device remains in RX mode and waits for incoming packet reception until the host requests a
different mode,
•
•
Single mode: the device returns automatically to STDBY_RC mode after packet reception,
Single mode with timeout: the device returns automatically to STDBY_RC mode after packet reception or after the
selected timeout,
•
Listen mode: the device alternate between Sleep and Rx mode until an IRQ is triggered.
In RX mode, BUSY will go low as soon as the RX is up and ready to receive data.
The SX1261 and SX1262 can operate in a Rx Boosted gain setup or in a Rx power saving gain setup. In the Rx power saving
gain, the radio will consume less power at a small cost in sensitivity. In Rx Boosted gain, the radio will consume more power
to improve the sensitivity.
Table 9-3: Rx Gain Configuration
Rx Gain
Register Address
Value
Rx Power Saving gain: 0x94 (default)
Rx Boosted gain: 0x96
0x08AC
Rx Gain
Note:
In LoRa® mode, the user can also use the command SetLoRaSymbNumTimeout(...) to perform a quick and immediate
assessment of the presence (or not) of LoRa preamble symbols. If the user defined parameter SymbNum is different from
0, the modem will wait for a total of SymbNum LoRa® symbol to validate, or not, the correct detection of a LoRa® packet. If
the various states of the demodulator are not lock at this moment, the radio will generate the RxTimeout IRQ. Otherwise,
the radio will stay in Rx for the full duration of the packet. For more information, please see Section 13.4.9
"SetLoRaSymbNumTimeout" on page 93.
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9.7 Transmit (TX) Mode
In TX mode after ramping-up the Power-Amplifier (PA) transmits the data buffer. In TX mode the circuit can operate in
different sub-modes: single mode or single with timeout mode.
The timeout in Tx mode can be used as a security to ensure that if for any reason the Tx is aborted or does not succeed (ie.
the TxDone IRQ never is never triggered), the TxTimeout will prevent the system from waiting for an unknown amount of
time. Using the timeout while in Tx mode remove the need to use resources from the host MCU to perform the same task.
In TX mode, BUSY will go low as soon as the PA has ramped-up and transmission of preamble starts.
9.7.1 PA Ramping
The ramping of the PA can be selected while setting the output power by using the command SetTxParams(...).
The PA ramp time can be selected to go from 10 s up to 3.4 ms.
9.8 Active Mode Switching Time
For more details on active mode switching time, see Section 8.3.1 "BUSY Control Line" on page 51.
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9.9 Transceiver Circuit Modes Graphical Illustration
All of the device operating modes and the states through which each mode selection transitions is shown here:
reset
POWER ON
or
RESET
RTC or NSS (SPI Operation)
startup
sleep
SetStandby()
STDBY
SetStandby()
RxDone, RxTimeout
SetStandby()
TxDone, TxTimeout
RxTxTimeout
(duty cycled operation)
FS
SetRx()
SetTx()
Rx
Tx
RxDone
Figure 9-1: Transceiver Circuit Modes
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10. Host Controller Interface
Through the SPI interface, the host can issue commands to the chip or access the data memory space to directly retrieve or
write data. In normal operation, a reduced number of direct data write operations is required except for data buffer.
The user interacts with the circuit through an API (instruction set).
The SX1261 uses the pin BUSY to indicate the status of the chip and its ability (or not) to receive another command while it
is doing its internal processing. Prior to executing one of the generic functions, it is thus necessary to check the status of
BUSY to make sure the chip is in a state where it can process another function.
10.1 Command Structure
In case of a command that does not require any parameter, the host sends only the opcode (1 byte).
In case of a command which requires one or several parameters, the opcode byte is followed immediately by parameter
bytes with the NSS rising edge terminating the command.
Table 10-1: SPI Interface Command Sequence
Byte
0
[1:n]
Data from host
Data to host
Opcode
RFU
Parameters
Status
10.2 Transaction Termination
The host terminates an SPI transaction with the rising NSS signal; the host does not explicitly send the command length as
a parameter. The host must not raise NSS within the bytes of a transaction.
If a transaction sends a command requiring parameters, all the parameters must be sent before rising NSS. If not the chip
will take some unknown value for the missing parameters.
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11. List of Commands
The following tables give the list of commands and their corresponding opcode. Unless specified, all parameters are 8-bit
values.
11.1 Operational Modes Commands
These functions have a direct impact on the behaviour of the device. They control the internal state machine to transmit or
receive packets, and all the modes in-between.
Table 11-1: Commands Selecting the Operating Modes of the Radio
Command
Opcode
Parameters
Description
SetSleep
0x84
sleepConfig
Set Chip in SLEEP mode
Set Chip in STDBY_RC or STDBY_XOSC
mode
SetStandby
0x80
standbyConfig
SetFs
SetTx
SetRx
0xC1
0x83
0x82
-
Set Chip in Freqency Synthesis mode
Set Chip in Tx mode
timeout[23:0]
timeout[23:0]
Set Chip in Rx mode
Stop Rx timeout on Sync Word/Header or
preamble detection
StopTimerOnPreamble
SetRxDutyCycle
0x9F
0x94
StopOnPreambleParam
Store values of RTC setup for listen mode
and if period parameter is not 0, set chip
into RX mode
rxPeriod[23:0], sleepPeriod[23:0]
Set chip into RX mode with passed CAD
parameters
SetCad
0xC5
0xD1
0xD2
0x96
0x89
0x98
-
Set chip into TX mode with infinite carrier
wave settings
SetTxContinuousWave
SetTxInfinitePreamble
SetRegulatorMode
Calibrate
-
Set chip into TX mode with infinite
preamble settings
-
Select LDO or DC_DC+LDO for CFG_XOSC,
FS, RX or TX mode
regModeParam
calibParam
freq1, freq2
Calibrate the RC13, RC64, ADC , PLL, Image
according to parameter
Launches an image calibration at the given
frequencies
CalibrateImage
Configure the Duty Cycle, Max output
power, device for the PA for SX1261 or
SX1262
SetPaConfig
0x95
0x93
paDutyCycle, HpMax, deviceSel, paLUT
fallbackMode
Defines into which mode the chip goes
after a TX / RX done.
SetRxTxFallbackMode
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11.2 Register and Buffer Access Commands
Table 11-2: Commands to Access the Radio Registers and FIFO Buffer
Command
Opcode
Parameters
Description
WriteRegister
ReadRegister
WriteBuffer
ReadBuffer
0x0D
0x1D
0x0E
0x1E
address[15:0], data[0:n]
address[15:0]
offset, data[0:n]
offset
Write into one or several registers
Read one or several registers
Write data into the FIFO
Read data from the FIFO
11.3 DIO and IRQ Control
Table 11-3: Commands Controlling the Radio IRQs and DIOs
Command
Opcode
Parameters
Description
IrqMask[15:0],
Dio1Mask[15:0],
Dio2Mask[15:0],
Dio3Mask[15:0],
SetDioIrqParams
0x08
Configure the IRQ and the DIOs attached to each IRQ
GetIrqStatus
ClearIrqStatus
0x12
0x02
0x9D
0x97
-
Get the values of the triggered IRQs
Clear one or several of the IRQs
-
SetDIO2AsRfSwitchCtrl
SetDIO3AsTcxoCtrl
enable
Configure radio to control an RF switch from DIO2
Configure the radio to use a TCXO controlled by DIO3
tcxoVoltage, timeout[23:0]
11.4 RF, Modulation and Packet Commands
Table 11-4: Commands Controlling the RF and Packets Settings
Command
Opcode
Parameters
Description
SetRfFrequency
0x86
rfFreq[23:0]
Set the RF frequency of the radio
Select the packet type corresponding
to the modem
SetPacketType
GetPacketType
SetTxParams
0x8A
0x11
0x8E
protocol
Get the current packet configuration
for the device
-
Set output power and ramp time for
the PA
power, rampTime
Compute and set values in selected
protocol modem for given
modulation parameters
SetModulationParams
0x8B
modParam1, modParam2, modParam3
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Table 11-4: Commands Controlling the RF and Packets Settings
Command
Opcode
Parameters
Description
packetParam1, packetParam2, packetParam3,
packetParam4, packetParam5, packetParam6,
packetParam7, packetParam8, packetParam9
Set values on selected protocol
modem for given packet parameters
SetPacketParams
0x8C
cadSymbolNum, cadDetPeak, cadDetMin,
cadExitMode, cadTimeout
Set the parameters which are used for
performing a CAD (LoRa® only)
SetCadParams
0x88
0x8F
0xA0
Store TX and RX base address in regis-
ter of selected protocol modem
SetBufferBaseAddress
SetLoRaSymbNumTimeout
TxbaseAddr, RxbaseAddr
SymbNum
Set the number of symbol the modem
has to wait to validate a lock
11.5 Status Commands
Table 11-5: Commands Returning the Radio Status
Command
Opcode
Parameters
Description
GetStatus
GetRssiInst
0xC0
0x15
0x13
-
-
-
Returns the current status of the device
Returns the instantaneous measured RSSI while in Rx mode
Returns PaylaodLengthRx(7:0), RxBufferPointer(7:0)
GetRxBufferStatus
Returns RssiAvg, RssiSync, PStatus2, PStaus3, PStatus4 in
FSK protocol, returns RssiPkt, SnrPkt in LoRa® protocol
GetPacketStatus
GetDeviceErrors
ClearDeviceErrors
0x14
0x17
0x07
-
-
Returns the error which has occurred in the device
Clear all the error(s). The error(s) cannot be cleared
independently
0x00
GetStats
0x10
0x00
-
-
Returns statistics on the last few received packets
Resets the value read by the command GetStats
ResetStats
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12. Register Map
12.1 Register Table
Table 12-1: List of Registers
Regiser Name
Address
0x06B8
Reset Value
0xX1
Function
Whitening initial value MSB
Whitening initial value LSB
Initial value used for the whitening LFSR in
FSK mode. The user should not change the
value of the 7 MSB of this register
0x06B9
0x00
CRC MSB Initial Value [0]
CRC LSB Initial Value [1]
CRC MSB polynomial Value [0]
CRC LSB polynomial Value [1]
SyncWord[0]
0x06BC
0x06BD
0x06BE
0x06BF
0x06C0
0x06C1
0x06C2
0x06C3
0x06C4
0x06C5
0x06C6
0x06C7
0x06CD
0x06CE
0x0740
0x1D
Initial value used for the polynomial used to
compute the CRC in FSK mode
0x0F
0x10
Polynomial used to compute the CRC in FSK
mode
0x21
-
1st byte of the Sync Word in FSK mode
2nd byte of the Sync Word in FSK mode
3rd byte of the Sync Word in FSK mode
4th byte of the Sync Word in FSK mode
5th byte of the Sync Word in FSK mode
6th byte of the Sync Word in FSK mode
7th byte of the Sync Word in FSK mode
8th byte of the Sync Word in FSK mode
Node Address used in FSK mode
SyncWord[1]
-
SyncWord[2]
-
SyncWord[3]
-
SyncWord[4]
-
SyncWord[5]
-
SyncWord[6]
-
SyncWord[7]
-
Node Address
0x00
0x00
0x14
Broadcast Address
LoRa Sync Word MSB
Broadcast Address used in FSK mode
Differentiate the LoRa® signal for Public or
Private Network
Set to 0x3444 for Public Network
Set to 0x1424 for Private Network
LoRa Sync Word LSB
0x0741
0x24
RandomNumberGen[0]
RandomNumberGen[1]
RandomNumberGen[2]
RandomNumberGen[3]
0x0819
0x081A
0x081B
0x081C
-
-
-
-
Can be used to get a 32-bit random number
Set the gain used in Rx mode:
Rx Power Saving gain: 0x94
Rx Boosted gain: 0x96
Rx Gain
0x08AC
0x94
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Table 12-1: List of Registers
Regiser Name
Address
Reset Value
Function
Set the Over Current Protection level.
The value is changed internally depending
on the device selected. Default values are:
OCP Configuration
0x08E7
0x18
SX1262: 0x38 (140 mA)
SX1261: 0x18 (60 mA)
Value of the trimming cap on XTA pin
XTA trim
XTB trim
0x0911
0x0912
0x05
0x05
This register should only be changed while
the radio is in STDBY_XOSC mode.
Value of the trimming cap on XTB pin
This register should only be changed while
the radio is in STDBY_XOSC mode.
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13. Commands Interface
13.1 Operational Modes Functions
13.1.1 SetSleep
The command SetSleep(...) is used to set the device in SLEEP mode with the lowest current consumption possible. This
command can be sent only while in STDBY mode (STDBY_RC or STDBY_XOSC). After the rising edge of NSS, all blocks are
switched OFF except the backup regulator if needed and the blocks specified in the parameter sleepConfig.
Table 13-1: SetSleep SPI Transaction
Byte
0
1
Data from host
Opcode = 0x84
sleepConfig
The sleepConfig argument is defined in Table 13-2.
Table 13-2: Sleep Mode Definition
SleepConfig[7:3]
SleepConfig [2]
SleepConfig [1]
SleepConfig [0]
RESERVED
0: cold start
0: RFU
0: RTC timeout disable
1: warm start
(device configuration in
retention) 1
1: wake-up on RTC timeout
(RC64k)
RESERVED
0: RFU
1. Note that only configuration for the activated modem before going to sleep is retained. Configuration of the other modems is lost and must be
re-configured.
When entering SLEEP mode, the BUSY line goes up and stays at a high level for the complete duration of the SLEEP period.
Once in SLEEP mode, it is possible to wake the device up from the host processor with a falling edge on the NSS line. The
device can also wake up automatically based on a counter event driven by the RTC 64 kHz clock. If the RTC is used, a rising
edge of NSS will still wake up the chip (the host keeps control of the chip).
By default, when entering into SLEEP mode, the chip configuration is lost. However, being able to store chip configuration
to lower host interaction or during RxDutyCycle mode is a must that can be done using the register in retention mode
during SLEEP state. This is available when the SetSleep(...) command is sent with sleepConfig[2] set to 1. Once the chip leaves
SLEEP mode (by NSS or RTC event), the chip will first restore the registers with the value stored into the retention register.
Caution:
Once sending the command SetSleep(...), the device will become unresponsive for around 500 s, time needed for the
configuration saving process and proper switch off of the various blocks. The user must thus make sure the device will not
be receiving SPI command during these 500 s to ensure proper operations of the device.
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13.1.2 SetStandby
The command SetStandby(...) is used to set the device in a configuration mode which is at an intermediate level of
consumption. In this mode, the chip is placed in halt mode waiting for instructions via SPI. This mode is dedicated to chip
configuration using high level commands such as SetPacketType(...).
By default, after battery insertion or reset operation (pin NRESET goes low), the chip will enter in STDBY_RC mode running
with a 13 MHz RC clock.
Table 13-3: SetConfig SPI Transaction
Byte
0
1
Data from host
Opcode = 0x80
StdbyConfig
The StdbyConfig byte definition is as follows:
Table 13-4: STDBY Mode Configuration
StdbyConfig
Value
Description
STDBY_RC
0
1
Device running on RC13M, set STDBY_RC mode
STDBY_XOSC
Device running on XTAL 32MHz, set STDBY_XOSC mode
13.1.3 SetFs
The command SetFs() is used to set the device in the frequency synthesis mode where the PLL is locked to the carrier
frequency. This mode is used for test purposes of the PLL and can be considered as an intermediate mode. It is
automatically reached when going from STDBY_RC mode to TX mode or RX mode.
Table 13-5: SetFs SPI Transaction
Byte
0
Data from host
Opcode = 0xC1
In FS mode, the PLL will be set to the frequency programmed by the function SetRfFrequency(...) which is the same used for
TX or RX operations.
13.1.4 SetTx
The command SetTx() sets the device in transmit mode.
Table 13-6: SetTx SPI Transaction
Byte
0
1-3
Data from host
Opcode = 0x83
timeout(23:0)
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•
Starting from STDBY_RC mode, the oscillator is switched ON followed by the PLL, then the PA is switched ON and the
PA regulator starts ramping according to the ramping time defined by the command SetTxParams(...)
•
•
When the ramping is completed the packet handler starts the packet transmission
When the last bit of the packet has been sent, an IRQ TX_DONE is generated, the PA regulator is ramped down, the PA
is switched OFF and the chip goes back to STDBY_RC mode
•
•
A TIMEOUT IRQ is triggered if the TX_DONE IRQ is not generated within the given timeout period
The chip goes back to STBY_RC mode after a TIMEOUT IRQ or a TX_DONE IRQ.
The timeout duration can be computed with the formula:
Timeout duration = Timeout * 15.625 µs
Timeout is a 23-bit parameter defining the number of step used during timeout as defined in the following table.
Table 13-7: SetTx Timeout Duration
Timeout(23:0)
Timeout Duration
Timeout disable, Tx Single mode, the device will stay in TX Mode until the packet is transmitted and returns
in STBY_RC mode upon completion.
0x000000
Timeout active, the device remains in TX mode, it returns automatically to STBY_RC mode on timer
end-of-count or when a packet has been transmitted. The maximum timeout is then 262 s.
Others
The value given for the timeout should be calculated for a given packet size, given modulation and packet parameters. The
timeout behaves as a security in case of conflicting commands from the host controller.
The timeout in Tx mode can be used as a security to ensure that if for any reason the Tx is aborted or does not succeed (ie.
the TxDone IRQ never is never triggered), the TxTimeout will prevent the system from waiting for an unknown amount of
time. Using the timeout while in Tx mode remove the need to use resources from the host MCU to perform the same task.
13.1.5 SetRx
The command SetRx() sets the device in receiver mode.
Table 13-8: SetRx SPI Transaction
Byte
0
1-3
Data from host
Opcode = 0x82
timeout(23:0)
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This command sets the chip in RX mode, waiting for the reception of one or several packets. The receiver mode operates
with a timeout to provide maximum flexibility to end users.
Table 13-9: SetRx Timeout Duration
Timeout15:0)
Timeout Duration
No timeout. Rx Single mode. The device will stay in RX Mode until a reception occurs and the devices return
in STBY_RC mode upon completion
0x000000
Rx Continuous mode. The device remains in RX mode until the host sends a command to change the
operation mode. The device can receive several packets. Each time a packet is received, a packet done
indication is given to the host and the device will automatically search for a new packet.
0xFFFFFF
Others
Timeout active. The device remains in RX mode, it returns automatically to STBY_RC mode on timer
end-of-count or when a packet has been received. As soon as a packet is detected, the timer is automatically
disabled to allow complete reception of the packet. The maximum timeout is then 262 s.
When the timeout is active (0x000000 < timeout < 0xFFFFFF), the radio will stop the reception at the end of the timeout
period unless a preamble and Sync Word (in GFSK) or Header (in LoRa®) has been detected. This is to ensure that a valid
packet will not be dropped in the middle of the reception due to the pre-defined timeout. By default, the timer will be
stopped only if the Sync Word or header has been detected. However, it is also possible to stop the timer upon preamble
detection by using the command StopTimerOnPreamble(...).
13.1.6 StopTimerOnPreamble
The command StopTimerOnPreamble(...) allows the user to select if the timer is stopped upon preamble detection of Sync
Word / header detection.
Table 13-10: StopTimerOnPreamble SPI Transaction
Byte
0
1
Data from host
Opcode = 0x9F
StopOnPreambleParam
The enable byte definition is given in the following table.
Table 13-11: StopOnPreambParam Definition
StopOnPreambleParam
Value
Description
disable
enable
0x00
0x01
Timer is stopped upon Sync Word or Header detection
Timer is stopped upon preamble detection
By default, the timer is stopped only when the Sync Word (in GFSK) or Header (in LoRa®) has been detected. When the
function StopTimerOnPreamble(...) is used with the value enable at 0x01, then the timer will be stopped upon preamble
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detection and the device will stay in RX mode until a packet is received. It is important to notice that stopping the timer
upon preamble may cause the device to stay in Rx for an unexpected long period of time in case of false detection.
Radio Current
Preamble Detected
Or
SyncWord / Header Detected
timeout
time
Radio in STDBY_RC
Radio in RX mode
Radio in STDBY_RC
Radio in RX mode
Figure 13-1: Stopping Timer on Preamble or Header Detection
13.1.7 SetRxDutyCycle
This command sets the chip in sniff mode so that it regularly looks for new packets. This is the listen mode.
Table 13-12: SetRxDutyCycle SPI Transaction
Byte
0
1-3
4-6
Data from host
Opcode= 0x94
rxPeriod(23:0)
sleepPeriod(23:0)
When this command is sent in STDBY_RC mode, the context (device configuration) is saved and the chip enters in a loop
defined by the following steps:
•
The chip enters RX and listens for a packet for a period of time defined by rxPeriod
•
•
•
The chip is looking for a preamble in either LoRa® or FSK
Upon preamble detection, the timeout is stopped and restarted with the value 2 * rxPeriod + sleepPeriod
If no packet is received during the RX window (defined by rxPeriod), the chip goes into SLEEP mode with context saved
for a period of time defined by sleepPeriod
•
At the end of the SLEEP window, the chip automatically restarts the process of restoring context and enters the RX
mode, and so on. At any time, the host can stop the procedure.
The loop is terminated if either:
•
A packet is detected during the RX window, at which moment the chip interrupts the host via the RX_DONE flag and
returns to STBY_RC mode
•
The host issues a SetStandby(...) command during the RX window (during SLEEP mode, the device is unable to receive
commands straight away and must first be waken up by a falling edge of NSS).
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The SLEEP mode duration is defined by:
Sleep Duration = sleepPeriod * 15.625 µs
The RX mode duration is defined by
Rx Duration = rxPeriod * 15.625 µs
The following figure highlights operations being performed while in RxDutyCycle mode. It can be observed that the radio
will spend around 1 ms to save the context and go into SLEEP mode and then re-initialize the radio, lock the PLL and go into
RX. The delay is not accurate and may vary depending on the time needed for the XTAL to start, the PLL to lock, etc.
Radio Current
rxPeriod
sleepPeriod
time
Radio in SLEEP mode
Radio in STDBY_RC
Radio in RX mode 500 us
500 us
Radio in RX mode
Figure 13-2: RX Duty Cycle Energy Profile
Upon preamble detection, the radio is set to look for a Sync Word (in GFSK) or a header (in LoRa®) and the timer is restarted
with a new value which is computed as 2 * rxPeriod + sleepPeriod. This is to ensure that the radio does not spend an
indefinite amount of time waiting in Rx for a packet which may never arrive (false preamble detection).
This implies a strong relationship between the time-on-air of the packet to be received, and the amount of time the radio
spends in RX and in SLEEP mode. If a long preamble is used on the TX side, care must be taken that the formula below is
respected:
T
+ T
≤ 2 * rxPeriod + sleepPeriod
header
preamble
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Radio Current
Preamble Detected
2 x rxPeriod + sleepPeriod
time
Radio in SLEEP mode
Radio in STDBY_RC
Radio in RX mode
500 us
Figure 13-3: RX Duty Cycle when Receiving
13.1.8 SetCAD
The command SetCAD() can be used only in LoRa® packet type. The Channel Activity Detection is a LoRa® specific mode of
operation where the device searches for the presence of a LoRa® preamble signal. After the search has completed, the
device returns in STDBY_RC mode. The length of the search is configured via the command SetCadParams(...). At the end of
the search period, the device triggers the IRQ CADdone if it has been enabled. If a valid signal has been detected it also
generates the IRQ CadDetected.
Table 13-13: SetCAD SPI Transaction
Byte
0
Data from host
Opcode = 0xC5
13.1.9 SetTxContinuousWave
SetTxContinuousWave() is a test command available for all packet types to generate a continuous wave (RF tone) at selected
frequency and output power. The device stays in TX continuous wave until the host sends a mode configuration command.
Table 13-14: SetTxContinuousWave SPI Transaction
Byte
0
Data from host
Opcode = 0xD1
While this command has no real use case in real life, it can provide valuable help to the developer to check and monitor the
performances of the radio while in Tx mode.
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13.1.10 SetTxInfinitePreamble
SetTxInfinitePreamble() is a test command to generate an infinite sequence of alternating zeros and ones in FSK modulation.
In LoRa®, the radio is only able to constantly modulate LoRa® preamble symbols. The device will remain in TX infinite
preamble until the host sends a mode configuration command.
While this command has no real use case in real life, it can provide valuable help to the developer to check and monitor the
performances of the radio while modulating in Tx mode.
Table 13-15: SendTxInfinitePreamble SPI Transaction
Byte
0
Data from host
Opcode = 0xD2
However, when using this function, it is impossible to define any data sent by the device. In LoRa® mode, the radio is only
able to constantly modulate LoRa preamble symbols and, in FSK mode, the radio is only able to generate FSK preamble
(0x55). Nevertheless, the end user will be able to easily monitor the spectral impact of its modulation parameters.
13.1.11 SetRegulatorMode
By default only the LDO is used. This is useful in low cost applications where the cost of the extra self needed for a DC-DC
converter is prohibitive. Using only a linear regulator implies that the RX or TX current is almost doubled. This function
allows to specify if DC-DC or LDO is used for power regulation. The regulation mode is defined by parameter
regModeParam.
Note:
This function is clearly related to the hardware implementation of the device. The user should always use this command
while knowing what has been implemented at the hardware level.
Table 13-16: SetRegulatorMode SPI Transaction
Byte
0
1
regModeParam
Data from host
Opcode= 0x96
0: Only LDO used for all modes
1: DC_DC+LDO used for STBY_XOSC,FS, RX and TX modes
13.1.12 Calibrate Function
At power up the radio performs calibration of RC64k, RC13M, PLL and ADC. It is however possible to launch a calibration of
one or several blocks at any time starting in STDBY_RC mode. The calibrate function starts the calibration of a block defined
by calibParam.
Table 13-17: Calibrate SPI Transaction
Byte
0
1
Data from host
Opcode = 0x89
calibParam
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The total calibration time if all blocks are calibrated is 3.5 ms. The calibration must be launched in STDBY_RC mode and the
BUSY pins will be high during the calibration process. A falling edge of BUSY indicates the end of the procedure.
Table 13-18: Calibration Setting
CalibParam
Calibration Setting
0: RC64k calibration disabled
1: RC64k calibration enabled
Bit 0
0: RC13Mcalibration disabled
1: RC13M calibration enabled
Bit 1
Bit 2
Bit 3
Bit 4
Bit 5
0: PLL calibration disabled
1: PLL calibration enabled
0: ADC pulse calibration disabled
1: ADC pulse calibration enabled
0: ADC bulk N calibration disabled
1: ADC bulk N calibration enabled
0: ADC bulk P calibration disabled
1: ADC bulk P calibration enabled
0: Image calibration disabled
1: Image calibration enabled
Bit 6
Bit 7
0: RFU
13.1.13 CalibrateImage
The function CalibrateImage(...) allows the user to calibrate the image rejection of the device for the device operating
frequency band.
Table 13-19: CalibrateImage SPI Transaction
Byte
0
1
2
Data from host
Opcode = 0x98
freq1
freq2
For more details on the specific frequency bands, see Section 9.2.1 "Image Calibration for Specific Frequency Bands" on
page 55.
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13.1.14 SetPaConfig
SetPaConfig is the command which is used to differentiate the SX1261 from the SX1262. When using this command, the
user selects the PA to be used by the device as well as its configuration.
Table 13-20: SetPaConfig SPI Transaction
Byte
0
1
2
3
4
deviceSel
0: SX1262
1: SX1261
paLut
Data from host
Opcode = 0x95
paDutyCycle
hpMax
reserved and
always 0x01
paDutyCycle controls the duty cycle (conduction angle) of both PAs (SX1261 and SX1262). The maximum output power, the
power consumption, and the harmonics will drastically change with paDutyCycle. The values given across this datasheet
are the recommended settings to achieve the best efficiency of the PA. Changing the paDutyCycle will affect the
distribution of the power in the harmonics and should thus be selected to work in conjunction of a given matching
network.
hpMax selects the size of the PA in the SX1262, this value has no influence on the SX1261. The maximum output power can
be reduced by reducing the value of hpMax. The valid range is between 0x00 and 0x07 and 0x07 is the maximum supported
value for the SX1262 to achieve +22 dBm output power. Increasing hpMax above 0x07 could cause early aging of the device
of could damage the device when used in extreme temperatures.
deviceSel is used to select either the SX1261 or the SX1262.
paLut is reserved and has always the value 0x01.
13.1.14.1 PA Optimal Settings
PA optimal settings are used to maximize the PA efficiency when the requested output power is lower than the nominal
+22 dBm (SX1262) or +14/15 dBm (SX1261). For example, the maximum output power in Japan is +10 dBm, and in China it
is +17 dBm in some bands. Those optimal settings require:
•
•
a dedicated matching / PA load impedance
a specific tweaking of the PA settings, described in Table 13-21: PA Operating Modes with Optimal Settings
Table 13-21: PA Operating Modes with Optimal Settings
Value in
SetTxParams1
Output
Power
paDutyCycle
hpMax
deviceSel
paLut
Mode
+15 dBm
+14 dBm
+10 dBm
0x06
0x04
0x01
0x00
0x00
0x00
0x01
0x01
0x01
0x01
0x01
0x01
+14 dBm
+14 dBm
+13 dBm
SX1261
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Table 13-21: PA Operating Modes with Optimal Settings
Value in
SetTxParams1
Output
Power
paDutyCycle
hpMax
deviceSel
paLut
Mode
+22 dBm
+20 dBm
+17 dBm
+14 dBm
0x04
0x03
0x02
0x02
0x07
0x05
0x03
0x02
0x00
0x00
0x00
0x00
0x01
0x01
0x01
0x01
+22 dBm
+22 dBm
+22 dBm
+14 dBm
SX1262
1. See Section 13.4.4 "SetTxParams" on page 83.
Note:
These changes make the use of nominal power either sub-optimal or unachievable.
Caution!
The following restrictions must be observed to avoid voltage overstress on the PA, exceeding the maximum ratings
may cause irreversible damage to the device:
•
•
•
For SX1261 at synthesis frequency above 400 MHz, paDutyCycle should not be higher than 0x07.
For SX1261 at synthesis frequency below 400 MHz, paDutyCycle should not be higher than 0x04.
For SX1262, paDutyCycle should not be higher than 0x04.
13.1.15 SetRxTxFallbackMode
The command SetRxTxFallbackMode defines into which mode the chip goes after a successful transmission or after a packet
reception.
Table 13-22: SetRxTxFallbackMode SPI Transaction
Byte
0
1
Data from host
Opcode = 0x93
fallbackMode
The fallbackMode byte definition is given as follows:
Table 13-23: Fallback Mode Definition
Fallback Mode
Value
Description
FS
0x40
0x30
0x20
The radio goes into FS mode after Tx or Rx
The radio goes into STDBY_XOSC mode after Tx or Rx
The radio goes into STDBY_RC mode after Tx or Rx
STDBY_XOSC
STDBY_RC
By default, the radio will always return in STDBY_RC unless the configuration is changed by using this command. Changing
the default mode from STDBY_RC to STDBY_XOSC or FS will only have an impact on the switching time of the radio.
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13.2 Registers and Buffer Access
13.2.1 WriteRegister Function
The command WriteRegister(...) allows writing a block of bytes in a data memory space starting at a specific address. The
address is auto incremented after each data byte so that data is stored in contiguous memory locations. The SPI data
transfer is described in the following table.
Table 13-24: WriteRegister SPI Transaction
Byte
0
1
2
3
4
...
n
Data from
host
Opcode =
0x0D
address[15:8] address[7:0]
Status Status
data@address
Status
data@address+1
Status
...
...
data@address+ (n-3)
status
Data to host
RFU
13.2.2 ReadRegister Function
The command ReadRegister(...) allows reading a block of data starting at a given address. The address is auto-incremented
after each byte. The SPI data transfer is described in Table 13-25. Note that the host has to send an NOP after sending the 2
bytes of address to start receiving data bytes on the next NOP sent.
Table 13-25: ReadRegister SPI Transaction
Byte
0
1
2
3
4
5
...
n
Data from
host
Opcode
= 0x1D
address[15:8] address[7:0]
NOP
NOP
NOP
...
NOP
data@address+
(n-4)
Data to host
RFU
Status
Status
Status
data@address
data@address+1
...
13.2.3 WriteBuffer Function
This function is used to store data payload to be transmitted. The address is auto-incremented; when it exceeds the value
of 255 it is wrapped back to 0 due to the circular nature of the data buffer. The address starts with an offset set as a
parameter of the function. Table 13-26 describes the SPI data transfer.
Table 13-26: WriteBuffer SPI Transaction
Byte
0
1
2
3
...
n
Opcode =
0x0E
Data from host
Data to host
offset
Status
data@offset
Status
data@offset+1
Status
...
...
data@offset+(n-2)
Status
RFU
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13.2.4 ReadBuffer Function
This function allows reading (n-3) bytes of payload received starting at offset. Note that the NOP must be sent after sending
the offset.
Table 13-27: ReadBuffer SPI Transaction
Byte
0
1
2
3
4
...
n
Data from
host
Opcode
= 0x1E
offset
Status
NOP
NOP
NOP
...
...
NOP
Data to host
RFU
Status
data@offset
data@offset+1
data@offset+(n-3)
13.3 DIO and IRQ Control Functions
13.3.1 SetDioIrqParams
This command is used to set the IRQ flag.
Table 13-28: SetDioIrqParams SPI Transaction
Byte
0
1-2
3-4
5-6
7-8
SetDioIrqParams
(0x08)
Data from host
Irq Mask(15:0)
DIO1Mask(15:0)
DIO2Mask(15:0)
DIO3Mask(15:0)
13.3.2 IrqMask
The IrkMask masks or unmasks the IRQ which can be triggered by the device. By default, all IRQ are masked (all ‘0’) and the
user can enable them one by one (or several at a time) by setting the corresponding mask to ‘1’.
13.3.2.1 DioxMask
The interrupt causes a DIO to be set if the corresponding bit in DioxMask and the IrqMask are set. As an example, if bit 0 of
IrqMask is set to 1 and bit 0 of DIO1Mask is set to 1 then, a rising edge of IRQ source TxDone will be logged in the IRQ register
and will appear at the same time on DIO1.
One IRQ can be mapped to all DIOs, one DIO can be mapped to all IRQs (an OR operation is done) but some IRQ sources will
be available only on certain modes of operation and frames.
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In total there are 10 possible interrupt sources depending on the chosen frame and chip mode. Each one of them can be
enabled or masked. In addition, every one of them can be mapped to DIO1, DIO2 or DIO3. Note that if DIO2 or DIO3 are used
to control the RF Switch or the TCXO, the IRQ will not be generated even if it is mapped to the pins.
Table 13-29: IRQ Registers
Bit
0
IRQ
TxDone
Description
Packet transmission completed
Packet received
Protocol
All
1
RxDone
All
2
PreambleDetected
SyncWordValid
HeaderValid
HeaderErr
CrcErr
Preamble detected
All
3
Valid sync word detected
Valid LoRa header received
LoRa header CRC error
Wrong CRC received
FSK
4
LoRa®
LoRa®
All
5
6
7
CadDone
Channel activity detection finished
Channel activity detected
Rx or Tx timeout
LoRa®
LoRa®
All
8
CadDetected
Timeout
9
A dedicated 10-bit register called IRQ_reg is used to log IRQ sources. Each position corresponds to one IRQ source as
described in the table above. A set of user commands is used to configure IRQ mask, DIOs mapping and IRQ clearing as
explained in the following chapters.
13.3.3 GetIrqStatus
This command returns the value of the IRQ register.
Table 13-30: GetIrqStatus SPI Transaction
Byte
0
1
2-3
Data from host
Data to host
Opcode = 0x12
RFU
NOP
NOP
Status
IrqStatus(15:0)
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13.3.4 ClearIrqStatus
This command clears an IRQ flag in the IRQ register.
Table 13-31: ClearIrqStatus SPI Transaction
Byte
0
1-2
Data from host
Opcode = 0x02
ClearIrqParam(15:0)
This function clears an IRQ flag in the IRQ register by setting to 1 the bit of ClearIrqParam corresponding to the same
position as the IRQ flag to be cleared. As an example, if bit 0 of ClearIrqParam is set to 1 then IRQ flag at bit 0 of IRQ register
is cleared.
If a DIO is mapped to one single IRQ source, the DIO is cleared if the corresponding bit in the IRQ register is cleared. If DIO
is set to 0 with several IRQ sources, then the DIO remains set to one until all bits mapped to the DIO in the IRQ register are
cleared.
13.3.5 SetDIO2AsRfSwitchCtrl
This command is used to configure DIO2 so that it can be used to control an external RF switch.
Table 13-32: SetDIO2AsRfSwitchCtrl SPI Transaction
Byte
0
1
Data from host
Opcode = 0x9D
enable
When controlling the external RX switch, the pin DIO2 will toggle accordingly to the internal state machine. DIO2 will go
up a few microseconds before the ramp-up of the PA and will go back down to zero after the ramp-down of the PA.
The enable byte definition is given as follows:
Table 13-33: Enable Configuration Definition
Enable
Description
0
DIO2 is free to be used as an IRQ
DIO2 is selected to be used to control an RF switch. In this case:
1
DIO2 = 0 in SLEEP, STDBY_RX, STDBY_XOSC, FS and RX modes, DIO2 = 1 in TX mode
13.3.6 SetDIO3AsTCXOCtrl
This command is used to configure the chip for an external TCXO reference voltage controlled by DIO3.
Table 13-34: SetDIO3asTCXOCtrl SPI Transaction
Byte
0
1
2-4
Data from host
Opcode = 0x97
tcxoVoltage
timeout(23:0)
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When this command is used, the device now controls the TCXO itself through DIO3. When needed (in mode STDBY_XOSC,
FS, TX and RX), the internal state machine will set DIO3 to a predefined output voltage (control through the parameter
tcxoVoltage). Internally, the clock controller will wait for the 32 MHz to appear before releasing the internal state machine.
The time needed for the 32 MHz to appear and stabilize can be controlled through the parameter timeout. If the 32 MHz
from the TCXO is not detected internally at the end the timeout period, the error XOSC_START_ERR will be flagged in the
error controller.
The tcxoVoltage byte definition is given in as follows:
Table 13-35: tcxoVoltage Configuration Definition
tcxoVoltage
Description
0x00
0x01
0x02
0x03
0x04
0x05
0x06
0x07
DIO3 outputs 1.6 V to supply the TCXO
DIO3 outputs 1.7 V to supply the TCXO
DIO3 outputs 1.8 V to supply the TCXO
DIO3 outputs 2.2 V to supply the TCXO
DIO3 outputs 2.4 V to supply the TCXO
DIO3 outputs 2.7 V to supply the TCXO
DIO3 outputs 3.0 V to supply the TCXO
DIO3 outputs 3.3 V to supply the TCXO
The power regulation for tcxoVoltage is configured to be 200 mV below the supply voltage. This means that even if
tcxoVoltage is configured above the supply voltage, the supply voltage will be limited by: VDDop > VTCXO + 200 mV
The timeout duration is defined by
Timeout duration = Timeout *15.625 µs
Most TCXO will not be immediately ready at the desired frequency and will suffer from an initial setup time where the
frequency is gently drifting toward the wanted frequency. This setup time is different from one TCXO to another and is also
dependent on the TCXO manufacturer. To ensure this setup time does not have any effect on the modulation or packets,
the timeout value will internally gate the 32 MHz coming from the TCXO to give enough time for this initial drift to stabilize.
At the end of the timeout period, the internal block will stop gating the clock and the radio will carry on to the next step.
Note:
The user should take the timeout period into account when going into Tx or Rx mode from STDBY_RC mode. Indeed, the
time needed to switch modes will increase with the duration of timeout. To avoid increasing the switching mode time, the
user can first set the device in STDBY_XOSC which will switch on the TCXO and wait for the timeout period. Then, the user
can set the device into Tx or Rx mode without suffering from any delay additional to the internal processing.
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13.4 RF Modulation and Packet-Related Functions
13.4.1 SetRfFrequency
The command SetRfFrequency(...) is used to set the frequency of the RF frequency mode.
Table 13-36: SetRfFrequency SPI Transaction
Byte
0
1-4
Data from host
Opcode = 0x86
RfFreq(31:0)
The LSB of Freq is equal to the PLL step which is:
RF
*F
Freq XTAL
RF
= ------------------------------------------
frequency
25
2
SetRfFrequency(...) defines the chip frequency in FS, TX and RX modes. In RX, the frequency is internally lowered to IF (250
kHz by default).
13.4.2 SetPacketType
The command SetPacketType(...) sets the SX1261 radio in LoRa® or in FSK mode. The command SetPacketType(...) must be
the first of the radio configuration sequence. The parameter for this command is PacketType.
Table 13-37: SetPacketType SPI Transaction
Byte
0
1
Data from host
Opcode = 0x8A
PacketType
Table 13-38: PacketType Definition
PacketType
Value
Modem Mode of Operation
PACKET_TYPE_GFSK
PACKET_TYPE_LORA
0x00
0x01
GFSK packet type
LORA mode
Changing from one mode of operation to another is done using the command SetPacketType(...) . The parameters from the
previous mode are not kept internally. The switch from one frame to another must be done in STDBY_RC mode.
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13.4.3 GetPacketType
The command GetPacketType() returns the current operating packet type of the radio.
Table 13-39: GetPacketType SPI Transaction
Byte
0
1
2
Data from host
Data to host
Opcode = 0x11
RFU
NOP
NOP
Status
packetType
13.4.4 SetTxParams
This command sets the TX output power by using the parameter power and the TX ramping time by using the parameter
RampTime. This command is available for all protocols selected.
Table 13-40: SetTxParams SPI Transaction
Byte
0
1
2
Data from host
Opcode = 0x8E
power
RampTime
The output power is defined as power in dBm in a range of
•
•
- 17 (0xEF) to +14 (0x0E) dBm by step of 1 dB if low power PA is selected
- 9 (0xF7) to +22 (0x16) dBm by step of 1 dB if high power PA is selected
Selection between high power PA and low power PA is done with the command SetPaConfig and the parameter deviceSel.
By default low power PA and +14 dBm are set.
The power ramp time is defined by the parameter RampTime as defined in the following table:
Table 13-41: RampTime Definition
RampTime
Value
RampTime (μs)
SET_RAMP_10U
SET_RAMP_20U
SET_RAMP_ 40U
SET_RAMP_80U
SET_RAMP_200U
SET_RAMP_800U
SET_RAMP_1700U
SET_RAMP_3400U
0x00
0x01
0x02
0x03
0x04
0x05
0x06
0x07
10
20
40
80
200
800
1700
3400
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13.4.5 SetModulationParams
The command SetModulationParams(...) is used to configure the modulation parameters of the radio. Depending on the
packet type selected prior to calling this function, the parameters will be interpreted differently by the chip.
Table 13-42: SetModulationParams SPI Transaction
Byte
0
1
2
3
4
5
6
7
8
Mod
Mod
Mod
Mod
Mod
Mod
Mod
Mod
Data from host for
Modulation Params
Opcode
0x8B
Param1
Param2
Param3
Param4
Param5
Param6
Param7
Param8
The meaning of the parameter depends on the selected protocol.
In FSK bitrate (BR) and Frequency Deviation (Fdev) are used for the transmission or reception. Bandwidth is used for
reception purpose. The pulse represents the Gaussian filter used to filter the modulation stream on the transmitter side.
In LoRa® packet type, SF corresponds to the Spreading Factor used for the LoRa® modulation. SF is defined by the parameter
Param[1]. BW corresponds to the bandwidth onto which the LoRa® signal is spread. BW in LoRa® is defined by the parameter
Param[2].
The LoRa® payload is fit with a forward error correcting mechanism which has several levels of encoding. The Coding Rate
(CR) is defined by the parameter Param[3] in LoRa®.
The parameter LdOpt corresponds to the Low Data Rate Optimization (LDRO). This parameter is usually set when the LoRa®
symbol time is equal or above 16.38 ms (typically for SF11 with BW125 and SF12 with BW125 and BW250). See
Section 6.1.1.4 "Low Data Rate Optimization" on page 39.
13.4.5.1 GFSK Modulation Parameters
The tables below provide more details on the GFSK modulation parameters:
Table 13-43: GFSK ModParam1, ModParam2 & ModParam3 - br
BR(23:0)
Description
0x000001 to 0xFFFFFF
br = 32 * Fxtal / bit rate
The bit rate is entered with the parameter br which is related to the frequency of the main oscillator (32 MHz). The bit rate
range is from 600 b/s up to 300 kb/s with a default value at 4.8 kb/s.
Table 13-44: GFSK ModParam4 - PulseShape
PulseShape
Description
0x00
0x08
0x09
0x0A
0x0B
No Filter applied
Gaussian BT 0.3
Gaussian BT 0.5
Gaussian BT 0.7
Gaussian BT 1
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Table 13-45: GFSK ModParam5 - Bandwidth
Bandwidth
Description
0x1F
0x17
0x0F
0x1E
0x16
0x0E
0x1D
0x15
0x0D
0x1C
0x14
0x0C
0x1B
0x13
0x0B
0x1A
0x12
0x0A
0x19
0x11
0x09
RX_BW_4800 (4.8 kHz DSB)
RX_BW_5800 (5.8 kHz DSB)
RX_BW_7300 (7.3 kHz DSB)
RX_BW_9700 (9.7 kHz DSB)
RX_BW_11700 (11.7 kHz DSB)
RX_BW_14600 (14.6 kHz DSB)
RX_BW_19500 (19.5 kHz DSB)
RX_BW_23400 (23.4 kHz DSB)
RX_BW_29300 (29.3 kHz DSB)
RX_BW_39000 (39 kHz DSB)
RX_BW_46900 (46.9 kHz DSB)
RX_BW_58600 (58.6 kHz DSB)
RX_BW_78200 (78.2 kHz DSB)
RX_BW_93800 (93.8 kHz DSB)
RX_BW_117300 (117.3 kHz DSB)
RX_BW_156200 (156.2 kHz DSB)
RX_BW_187200 (187.2 kHz DSB)
RX_BW_234300 (232.3 kHz DSB)
RX_BW_312000 (312 kHz DSB)
RX_BW_373600 (373.6 kHz DSB)
RX_BW_467000 (467 kHz DSB)
Table 13-46: GFSK ModParam6, ModParam7 & ModParam8 - Fdev
Fdev(23:0)
Description
Fdev = (Frequency Deviation * 2^25) / Fxtal
0x000000 to 0xFFFFFF
F
*F
dev XTAL
Frequencydeviation = -----------------------------------
25
2
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13.4.5.2 LoRa® Modulation Parameters
The tables below provide more details on the LoRa® modulation parameters:
Table 13-47: LoRa® ModParam1- SF
SF
Description
0x05
0x06
0x07
0x08
0x09
0x0A
0x0B
0x0C
SF5
SF6
SF7
SF8
SF9
SF10
SF11
SF12
Table 13-48: LoRa® ModParam2 - BW
BW
Description
0x00
0x08
0x01
0x09
0x02
0x0A
0x03
0x04
0x05
0x06
LORA_BW_7 (7.81 kHz real)
LORA_BW_10 (10.42 kHz real)
LORA_BW_15 (15.63 kHz real)
LORA_BW_20 (20.83 kHz real)
LORA_BW_31 (31.25 kHz real)
LORA_BW_41 (41.67 kHz real)
LORA_BW_62 (62.50 kHz real)
LORA_BW_125 (125 kHz real)
LORA_BW_250 (250 kHz real)
LORA_BW_500 (500 kHz real)
Table 13-49: LoRa® ModParam3 - CR
CR
Description
0x01
0x02
0x03
0x04
LORA_CR_4_5
LORA_CR_4_6
LORA_CR_4_7
LORA_CR_4_8
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Table 13-50: LoRa® ModParam4 - LowDataRateOptimize
LowDataRateOptimize
Description
0x00
0x01
LowDataRateOptimize OFF
LowDataRateOptimize ON
13.4.6 SetPacketParams
This command is used to set the parameters of the packet handling block.
Table 13-51: SetPacketParams SPI Transaction
Byte
0
1
2
3
4
5
6
7
8
9
Data from
host for
packet type
packet
packet
packet
packet
Param1
packet
Param2
packet
Param3
packet
Param4
packet
Param7
Opcode
= 0x8C
packet
Param5
Param6
Param8
Param9
13.4.6.1 GFSK Packet Parameters
The tables below provide more details on the GFSK packets parameters:
Table 13-52: GFSK PacketParam1 & PacketParam2 - PreambleLength
PreambleLength (15:0)
Description
Transmitted preamble length: number of bits sent as preamble
0x0001 to 0xFFFF
The preamble length is a 16-bit value which represents the number of bytes which will be sent by the radio. Each preamble
byte represents an alternate of 0 and 1 and each byte is coded as 0x55.
Table 13-53: GFSK PacketParam3 - PreambleDetectorLength
PreambleDetector
Description
0x00
0x04
0x05
0x06
0x07
Preamble detector length off
Preamble detector length 8 bits
Preamble detector length 16 bits
Preamble detector length 24 bits
Preamble detector length 32 bits
The preamble detector acts as a gate to the packet controller, when different from 0x00 (preamble detector length off), the
packet controller will only become active if a certain number of preamble bits have been successfully received by the radio.
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Table 13-54: GFSK PacketParam4 - SyncWordLength
SyncWordLength
Description
Sync Word length in bits (going from 0 to 8 bytes)
0x00 to 0x40
The Sync Word is directly programmed into the device through simple register access. The table below provide the
addresses to program the Sync Word value.
Table 13-55: Sync Word Programming
Sync Word
Register Address
Byte 0
Byte 1
Byte 2
Byte 3
Byte 4
Byte 5
Byte 6
Byte 7
0x06C0
0x06C1
0x06C2
0x06C3
0x06C4
0x06C5
0x06C6
0x06C7
Table 13-56: GFSK PacketParam5 - AddrComp
AddrComp
Description
0x00
0x01
0x02
Address Filtering Disable
Address Filtering activated on Node address
Address Filtering activated on Node and broadcast addresses
The node address and the broadcast address are directly programmed into the device through simple register access. The
tables below provide the addresses to program the values.
Table 13-57: Node Address Programming
Register Address
Default value
NodeAddrReg
0x06CD
0x00
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Table 13-58: Broadcast Address Programming
Register Address
Default value
BroadcastReg
0x06CE
0x00
Table 13-59: GFSK PacketParam6 - PacketType
PacketType
Description
The packet length is known on both sides, the size of the payload is not
added to the packet
0x00
0x01
The packet is on variable size, the first byte of the payload will be the
size of the packet
Table 13-60: GFSK PacketParam7 - PayloadLength
AddrComp
Description
Size of the payload (in bytes) to transmit or maximum size of the
payload that the receiver can accept.
0x00 to 0xFF
Table 13-61: GFSK PacketParam8 - CRCType
CRCType
Description
0x01
0x00
0x02
0x04
0x06
CRC_OFF (No CRC)
CRC_1_BYTE (CRC computed on 1 byte)
CRC_2_BYTE(CRC computed on 2 byte)
CRC_1_BYTE_INV(CRC computed on 1 byte and inverted)
CRC_2_BYTE_INV(CRC computed on 2 byte and inverted)
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In the SX1261 and SX1262, the CRC can be fully configured and the polynomial used, as well as the initial values can be
entered directly through register access.
Table 13-62: CRC Initial Value Programming
Register Address
Default Value
CRC MSB Initial Value [15:8]
CRC LSB Initial Value [7:0]
0x06BC
0x06BD
0x1D
0x0F
Table 13-63: CRC Polynomial Programming
Register Address
Default Value
CRC MSB polynomial value [15:8]
CRC LSB polynomial value [7:0]
0x06BE
0x06BF
0x10
0x21
Table 13-64: GFSK PacketParam9 - Whitening
AddrComp
Description
0x00
0x01
No encoding
Whitening enable
Table 13-65: Whitening Initial Value
Whitening initial value
Register Address
Default Value
Whitening initial value MSB
Whitening initial value LSB
0x06B8
0x06B9
0x01
0x00
13.4.6.2 LoRa® Packet Parameters
The tables below provide more details on the LoRa® packets parameters:
Table 13-66: LoRa® PacketParam1 & PacketParam2 - PreambleLength
PreambleLength (15:0)
Description
preamble length: number of symbols sent as preamble
0x0001 to 0xFFFF
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The preamble length is a 16-bit value which represents the number of LoRa® symbols which will be sent by the radio.
Table 13-67: LoRa® PacketParam3 - HeaderType
HeaderType
Description
0x00
0x01
Variable length packet (explicit header)
Fixed length packet (implicit header)
When the byte headerType is at 0x00, the payload length, coding rate and the header CRC will be added to the LoRa®
header and transported to the receiver.
Table 13-68: LoRa® PacketParam4 - PayloadLength
Payloadlength
Description
Size of the payload (in bytes) to transmit or maximum size of the
payload that the receiver can accept.
0x00 to 0xFF
Table 13-69: LoRa® PacketParam5 - CRCType
CRCType
Description
0x00
0x01
CRC OFF
CRC ON
Table 13-70: LoRa® PacketParam6 - InvertIQ
AddrComp
Description
0x00
0x01
Standard IQ setup
Inverted IQ setup
13.4.7 SetCadParams
The command SetCadConfig(...) defines the number of symbols on which CAD operates.
Table 13-71: SetCadParams SPI Transaction
Byte
0
1
2
3
4
6-7
Data from
host
Opcode = 0x88
cadSymbolNum
cadDetPeak
cadDetMin
cadExitMode
cadTimeout(23:0)
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The number of symbols used is defined in the following table.
Table 13-72: CAD Number of Symbol Definition
cadSymbolNum
Value
Number of Symbols used for CAD
CAD_ON_1_SYMB
CAD_ON_2_SYMB
CAD_ON_4_SYMB
CAD_ON_8_SYMB
CAD_ON_16_SYMB
0x00
0x01
0x02
0x03
0x04
1
2
4
8
16
The parameters cadDetPeak and cadDetMin defines the sensitivity of the LoRa modem when trying to corealate to actual
LoRa preamble symbols. These two settings depends on the LoRa spreading factor and Bandwidth, but also depends on
the number of symbol used to validate or not the detection.
Table 13-73: Recommended Settings for cadDetPeak and cadDetMin with 4 Symbols Detection
SF
cadDetPeak
cadDetMin
5
6
18
19
20
21
22
23
24
25
10
10
10
10
10
10
10
10
7
8
9
10
11
12
Choosing the right value is not easy and the values selected must be carefully tested to ensure a good detection at
sensitivity level, and also to limit the number of false detections.
The parameter cadExitMode defines the action to be done after a CAD operation. This is optional.
Table 13-74: CAD Exit Mode Definition
cadExitMode
Value
Operation
The chip performs the CAD operation in LoRa®. Once done and whatever the
activity on the channel, the chip goes back to STBY_RC mode.
CAD_ONLY
0x00
The chip performs a CAD operation and if an activity is detected, it stays in RX until
a packet is detected or the timer reaches the timeout defined by
CAD_RX
0x01
cadTimeout * 15.625 us
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The parameter cadTimeout is only used when the CAD is performed with cadExitMode = CAD_RX. Here, the cadTimeout
indicates the time the device will stay in Rx following a successful CAD.
Rx Timeout = cadTimeout * 15.625
13.4.8 SetBufferBaseAddress
This command sets the base addresses in the data buffer in all modes of operations for the packet handing operation in TX
and RX mode. The usage and definition of those parameters are described in the different packet type sections.
Table 13-75: SetBufferBaseAddress SPI Transaction
Byte
0
1
2
Data from host
Opcode = 0x8F
TX base address
RX base address
13.4.9 SetLoRaSymbNumTimeout
This command sets the number of symbols used by the modem to validate a successful reception.
Table 13-76: SetLoRaSymbNumTimeout SPI Transaction
Byte
0
1
Data from host
Opcode = 0xA0
SymbNum
In LoRa® mode, when going into Rx, the modem will lock as soon as a LoRa® symbol has been detected which may lead to
false detection. This phenomena is quite rare but nevertheless possible. To avoid this, the command
SetLoRaSymbNumTimeout can be used to define the number of symbols which will be used to validate the correct
reception of a packet.
When the SymbNum param is set the 0, the modem will validate the reception as soon as a LoRa® Symbol has been
detected.
When SymbNum is different from 0, the modem will wait for a total of SymbNum LoRa® symbol to validate, or not, the
correct detection of a LoRa® packet. If the various states of the demodulator are not lock at this moment, the radio will
generate the RxTimeout IRQ.
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13.5 Communication Status Information
These commands return the information about the chip status, and received packet such a packet length, received power
during packet, several flags indicating if the packet as been correctly received. The returned parameters differ for the LoRa®
protocol.
13.5.1 GetStatus
The host can retrieve chip status directly through the command GetStatus() : this command can be issued at any time and
the device returns the status of the device. The command GetStatus() is not strictly necessary since device returns status
information also on command bytes. The status byte returned is described in Table 13-77.
Table 13-77: Status Bytes Definition
7
6:4
3:1
0
Reserved
Chip mode
0x0: Unused
RFU
Command status
0x0: Reserved
RFU
Reserved
0x2: Data is available to host1
0x3: Command timeout2
0x2: STBY_RC
0x3: STBY_XOSC
0x4: FS
-
-
0x4: Command processing error3
0x5: Failure to execute command4
0x6: Command TX done5
0x5: RX
0x6: TX
1. A packet has been successfully received and data can be retrieved
2. A transaction from host took too long to complete and triggered an internal watchdog. The watchdog mechanism can be disabled by host; it
is meant to ensure all outcomes are flagged to the host MCU.
3. Processor was unable to process command either because of an invalid opcode or because an incorrect number of parameters has been
provided.
4. The command was successfully processed, however the chip could not execute the command; for instance it was unable to enter the specified
device mode or send the requested data,
5. The transmission of the current packet has terminated
The SPI transaction for the command GetStatus() is given in the following table.
Table 13-78: GetStatus SPI Transaction
Byte
0
1
Data from host
Data to host
Opcode = 0xC0
RFU
NOP
Status
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13.5.2 GetRxBufferStatus
This command returns the length of the last received packet (PayloadLengthRx) and the address of the first byte received
(RxStartBufferPointer). It is applicable to all modems. The address is an offset relative to the first byte of the data buffer.
Table 13-79: GetRxBufferStatus SPI Transaction
Byte
0
1
2
3
Data from host
Data to host
Opcode = 0x13
RFU
NOP
NOP
NOP
Status
PayloadLengthRx
RxStartBufferPointer
13.5.3 GetPacketStatus
Table 13-80: GetPacketStatus SPI Transaction
Byte
0
1
2
3
4
Opcode =
0x14
Data from host
NOP
NOP
NOP
NOP
Data to host for FSK packet type
Data to host for LORA packet type
RFU
RFU
Status
Status
RxStatus
RssiPkt
RssiSync
SnrPkt
RssiAvg
SignalRssiPkt
The next table gives the description of the different RSSI and SNR available on the chip depending on the packet type.
Table 13-81: Status Bit
RSSI
Description
bit 7: preamble err
bit 6: sync err
bit 5: adrs err
RxStatus
FSK
bit 4: crc err
bit 3: lenght err
bit 2: abort err
bit 1: pkt received
bit 0: pkt sent
RSSI value latched upon the detection of the sync address.
[negated, dBm, fixdt(0,8,1)]
RssiSync
FSK
Actual signal power is –RssiSync/2 (dBm)
RssiAvg
FSK
RSSI average value over the payload of the received packet. Latched upon the pkt_done IRQ.
[negated, dBm, fixdt(0,8,1)]
Actual signal power is –RssiAvg/2 (dBm)
RssiPkt
LoRa®
Average over last packet received of RSSI
Actual signal power is –RssiPkt/2 (dBm)
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Table 13-81: Status Bit
RSSI
Description
SnrPkt
LoRa®
Estimation of SNR on last packet received.In two’s compliment format multiplied by 4.
Actual SNR in dB =SnrPkt/4
Estimation of RSSI of the LoRa® signal (after despreading) on last packet received.In two’s compliment
format.[negated, dBm, fixdt(0,8,1)]
SignalRssiPkt
LoRa®
Actual Rssi in dB = -SignalRssiPkt/2
13.5.4 GetRssiInst
This command returns the instantaneous RSSI value during reception of the packet. The command is valid for all protocols.
Table 13-82: GetRssiInst SPI Transaction
Byte
0
1
2
Data from host
Opcode = 0x15
NOP
NOP
RssiInst
Data to host
RFU
Status
Signal power in dBm = –RssiInst/2 (dBm)
13.5.5 GetStats
This command returns the number of informations received on a few last packets. The command is valid for all protocols.
Table 13-83: GetStats SPI Transaction
Byte
0
1
2-3
4-5
6-7
Opcode =
0x10
Data from host
NOP
NOP
NOP
NOP
Data to host in GFSK
packet type
RFU
RFU
Status
Status
NbPktReceived(15:0)
NbPktReceived(15:0)
NbPktCrcError(15:0)
NbPktCrcError(15:0)
NbPktLengthError(15:0)
NbPktHeaderErr(15:0)
Data to host in LoRa®
packet type
13.5.6 ResetStats
This command resets the value read by the command GetStats. To execute this command, the opcode is 0x0 followed by
6 zeros (so 7 zeros in total).
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13.6 Miscellaneous
13.6.1 GetDeviceErrors
This commands returns possible errors flag that could occur during different chip operation as described below.
Table 13-84: GetDeviceErrors SPI Transaction
Byte
0
1
2-3
Data from host
Data to host
Opcode= 0x17
RFU
NOP
NOP
Status
OpError(15:0)
The following table gives the meaning of each OpError.
Table 13-85: OpError Bits
OpError
0
1
bit 0
bit 1
RC64K_CALIB_ERR
RC13M_CALIB_ERR
PLL_CALIB_ERR
ADC_CALIB_ERR
IMG_CALIB_ERR
XOSC_START_ERR
PLL_LOCK_ERR
RFU
RC64k calibration failed
RC13M calibration failed
PLL calibration failed
ADC calibration failed
IMG calibration failed
XOSC failed to start
PLL failed to lock
RFU
bit 2
bit 3
bit 4
bit 5
bit 6
bit 7
bit 8
PA_RAMP_ERR
RFU
PA ramping failed
RFU
bit 15:9
13.6.2 ClearDeviceErrors
This commands clears all the errors recorded in the device. The errors can not be cleared independently.
Table 13-86: ClearDeviceErrors SPI Transaction
Byte
0
1
Data from host
Data to host
Opcode= 0x07
RFU
0x00
Status
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14. Application
14.1 HOST API Basic Read Write Function
The communication with the SX1261/2 is organized around generic functions which allow the user to control the device
behavior. Each function is based on an Operational Command (refer throughout this document as “Opcode”), which is then
followed by a set of parameters. The SX1261/2 use the BUSY pin to indicate the status of the chip. In the following chapters,
it is assumed that host microcontroller has an SPI and access to it via spi.write(data). Data is an 8-bit word. The SPI chip select
is defined by NSS, active low.
14.2 Circuit Configuration for Basic Tx Operation
This chapter describes the sequence of operations needed to send or receive a frame starting from a power up.
After power up (battery insertion or hard reset) the chip runs automatically a calibration procedure and goes to STDBY_RC
mode. This is indicated by a low state on BUSY pin. From this state the steps are:
1. If not in STDBY_RC mode, then go to this mode with the command SetStandby(...)
2. Define the protocol (LoRa® or FSK) with the command SetPacketType(...)
3. Define the RF frequency with the command SetRfFrequency(...)
4. Define output power and ramping time with the command SetTxParams(...)
5. Define where the data payload will be stored with the command SetBufferBaseAddress(...)
6. Send the payload to the data buffer with the command WriteBuffer(...)
7. Define the modulation parameter according to the chosen protocol with the command SetModulationParams(...)
8. Define the frame format to be used with the command SetPacketParams(...)
9. Configure DIO and IRQ: use the command SetDioIrqParams(...) to select TxDone IRQ and map this IRQ to a DIO (DIO1,
DIO2 or DIO3)
10. Define Sync Word value: use the command WriteReg(...) to write the value of the register via direct register access
11. Set the circuit in transmitter mode to start transmission with the command SetTx(). Use the parameter to enable
Timeout
12. Wait for the IRQ TxDone or Timeout: once the packet has been sent the chip goes automatically to STDBY_RC mode
13. Clear the IRQ TxDone flag
SX1261/2
Data Sheet
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Semtech
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DS.SX1261-2.W.APP
December 2017
14.3 Circuit Configuration for Basic Rx Operation
This chapter describes the sequence of operations needed to receive a frame starting from a power up. This sequence is
valid for all protocols.
After power up (battery insertion or hard reset) the chip run automatically a calibration procedure and goes to STDBY_RC
mode. This is indicated by a low state on BUSY pin. From this state the steps are:
1. If not in STDBY_RC mode, then set the circuit in this mode with the command SetStandby()
2. Define the protocol (LoRa® or FSK) with the command SetPacketType(...)
3. Define the RF frequency with the command SetRfFrequency(...)
4. Define where the data will be stored inside the data buffer in Rx with the command SetBufferBaseAddress(...)
5. Define the modulation parameter according to the chosen protocol with the command SetModulationParams(...)
6. Define the frame format to be used with the command SetPacketParams(...)
7. Configure DIO and irq: use the command SetDioIrqParams(...) to select the IRQ RxDone and map this IRQ to a DIO (DIO1
or DIO2 or DIO3), set IRQ Timeout as well.
8. Define Sync Word value: use the command WriteReg(...) to write the value of the register via direct register access.
9. Set the circuit in reception mode: use the command SetRx(). Set the parameter to enable timeout or continuous mode
10. Wait for IRQ RxDone or Timeout: the chip will stay in Rx and look for a new packet if the continuous mode is selected
otherwise it will goes to STDBY_RC mode.
11. In case of the IRQ RxDone, check the status to ensure CRC is correct: use the command GetIrqStatus()
Note:
The IRQ RxDone means that a packet has been received but the CRC could be wrong: the user must check the CRC before
validating the packet.
12. Clear IRQ flag RxDone or Timeout : use the command ClearIrqStatus(). In case of a valid packet (CRC Ok), get the packet
length and address of the first byte of the received payload by using the command GetRxBufferStatus(...)
13. In case of a valid packet (CRC Ok), start reading the packet
14.4 Issuing Commands in the Right Order
Most of the commands can be sent in any order except for the radio configuration commands which will set the radio in
the proper operating mode. Indeed, it is mandatory to set the radio protocol using the command SetPacketType(...) as a first
step before issuing any other radio configuration commands. In a second step, the user should define the modulation
parameter according to the chosen protocol with the command SetModulationParams(...). Finally, the user should then
select the packet format with the command SetPacketParams(...).
Note:
If this order is not respected, the behavior of the device could be unexpected.
SX1261/2
Data Sheet
99 of 107
Semtech
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DS.SX1261-2.W.APP
December 2017
14.5 Application Schematics
14.5.1 Application Design of the SX1261 with RF Switch
R4
VR_PA
ANT_SW
100R
C14
1nF
C2
C1
L1
C4
L3
Q1 Xtal
GND
32.0MHz
3
GND
GND
C6
1
C16
U1
L4
C5
C7
2
4
U2
1
6
5
4
RFIO
GND
1
2
RF1
CTRL
RFC
CTRL
C8
L5
GND
VDD_IN
24
23
22
21
20
2
3
VR_PA
RFO
GND
RF2
SMA
GND
GND
XTA
XTB
3
XTA
GND
GND
GND
L8
4
C9
C10
RFI_N
RFI_P
GND
XTB
5
GND
C11
PE4259 RF Switch
GND
DIO3
6
DIO3
19 NSS
7
NSS
SCK
MOSI
MISO
NRESET
BUSY
DIO1
VREG
GND
18 SCK
17 MOSI
16 MISO
8
GND
GND
C13
L7 15uH
9
GND
DCC_SW
VBAT
VBAT_IO
DIO2
GND
L6
VDD_RADIO
10
11
12
15 SX_NRESET
14 BUSY
DIO2
C17
470nF
13 DIO1
C18
R3
DIO2
100nF
C12
100R
C15
1nF
SX1261
GND
GND
GND
GND
GND
Figure 14-1: Application Schematic of the SX1261 with RF Switch
14.5.2 Application Design of the SX1262 with RF Switch
R4
VR_PA
ANT_SW
100R
C14
1nF
VDD_RADIO
C2
C1
L1
C4
L3
Q1 Xtal
GND
32.0MHz
3
GND
GND
C6
1
C16
U1
L2
L4
C3
C5
C7
2
4
U2
1
6
5
4
RFIO
1
2
RF1
CTRL
RFC
CTRL
C8
L5
GND
VDD_IN
24
23
22
21
20
2
3
VR_PA
RFO
GND
RF2
SMA
GND
GND
XTA
XTB
3
XTA
GND
GND
GND
GND
4
RFI_N
RFI_P
GND
C9
C10
XTB
5
GND
C11
PE4259 RF Switch
GND
DIO3
6
DIO3
19 NSS
7
NSS
SCK
MOSI
MISO
NRESET
BUSY
DIO1
VREG
GND
18 SCK
17 MOSI
16 MISO
8
GND
GND
GND
C13
L7 15uH
9
GND
DCC_SW
VBAT
VBAT_IO
DIO2
GND
L6
VDD_RADIO
10
11
12
15 SX_NRESET
14 BUSY
DIO2
C17
470nF
13 DIO1
C18
R3
DIO2
100nF
C12
100R
C15
1nF
SX1262
GND
GND
GND
GND
GND
Figure 14-2: Application Schematic of the SX1262 with RF Switch
Note:
The application schematics presented here are for information only.
Always refer to the latest reference designs posted on www.semtech.com.
Note:
Recommendations for heat dissipation techniques to be applied to the PCB designs are given in detail in the application
note AN1200.37 “Recommendations for Best Performance” on www.semtech.com.
In miniaturized design implementations where heat dissipations techniques cannot be implemented or the use of the
LowDataRateOptimize is not supported, the use of a TCXO will provide a more stable clock reference.
SX1261/2
Data Sheet
100 of 107
Semtech
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Rev. 1.1
DS.SX1261-2.W.APP
December 2017
15. Packaging Information
15.1 Package Outline Drawing
The transceiver is delivered in a 4x4mm QFN package with 0.5 mm pitch:
Figure 15-1: QFN 4x4 Package Outline Drawing
SX1261/2
Data Sheet
101 of 107
Semtech
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Rev. 1.1
DS.SX1261-2.W.APP
December 2017
15.2 Package Marking
ꢀꢁ
ꢀꢁ
ꢀꢁꢂꢀꢃ
ꢀꢁꢂꢁꢃ
ꢀꢁꢂꢃꢀ
ꢀꢁꢂꢃꢀ
ꢀꢀꢁꢂꢃ
ꢀꢀꢁꢂꢃ
ꢀꢀꢀꢀꢀꢁ
ꢀꢀꢀꢀꢀꢁ
ꢀ&5/.2,<+35<6-*<ꢁ<9<ꢁ<11<ꢀꢂꢃꢄ<ꢅꢁ<ꢂ*&)<4&(/&,*ꢆ<
;2222< ꢇ< ꢃ&56<ꢈ71'*5<ꢉꢊ9&140*ꢆ<ꢋꢌꢅꢍꢌꢎ
::8< ꢇ< ꢏ&6*<ꢐ3)*<ꢉꢌꢑꢒꢅꢎ<
99999< ꢇ< *16*(-<ꢂ36<ꢈ71'*5<ꢉꢊ9&140*ꢆ<ꢊꢀꢁꢂꢁꢀ<
Figure 15-2: SX1261/2 Marking
15.3 Land Pattern
The recommended land pattern is as follows:
Figure 15-3: QFN 4x4mm Land Pattern
SX1261/2
Data Sheet
102 of 107
Semtech
www.semtech.com
Rev. 1.1
DS.SX1261-2.W.APP
December 2017
15.4 Reflow Profiles
Reflow process instructions are available from the Semtech website, at the following address:
http://www.semtech.com/quality/ir_reflow_profiles.html
The transceiver uses a QFN24 4x4 mm package, also named MLP package.
SX1261/2
Data Sheet
103 of 107
Semtech
www.semtech.com
Rev. 1.1
DS.SX1261-2.W.APP
December 2017
Glossary
List of Acronyms and their Meaning
Acronym
Meaning
ACR
ADC
API
Adjacent Channel Rejection
Analog-to-Digital Converter
Application Programming Interface
Modulation Index
β
BER
BR
Bit Error Rate
Bit Rate
BT
Bandwidth-Time bit period product
BandWidth
BW
CAD
CPOL
CPHA
CR
Channel Activity Detection
Clock Polarity
Clock Phase
Coding Rate
CRC
CW
Cyclical Redundancy Check
Continuous Wave
DIO
DSB
ECO
FDA
FEC
FIFO
FSK
Digital Input / Output
Double Side Band
Engineering Change Order
Frequency Deviation
Forward Error Correction
First In First Out
Frequency Shift Keying
Gaussian Frequency Shift Keying
Gaussian Minimum Shift Keying
Gross Die Per Wafer
GFSK
GMSK
GDPW
IF
Intermediate Frequencies
Interrupt Request
IRQ
ISM
LDO
LDRO
Industrial, Scientific and Medical (radio spectrum)
Low-Dropout
Low Data Rate Optimization
SX1261/2
Data Sheet
104 of 107
Semtech
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Rev. 1.1
DS.SX1261-2.W.APP
December 2017
List of Acronyms and their Meaning
Acronym
Meaning
LFSR
LNA
LO
Linear-Feedback Shift Register
Low-Noise Amplifier
Local Oscillator
Long Range Communication
LoRa®
the LoRa® Mark is a registered trademark of the Semtech Corporation
LSB
MISO
MOSI
MSB
MSK
NOP
NRZ
NSS
OCP
PA
Least Significant Bit
Master Input Slave Output
Master Output Slave Input
Most Significant Bit
Minimum-Shift Keying
No Operation (0x00)
Non-Return-to-Zero
Slave Select active low
Over Current Protection
Power Amplifier
PER
Packet Error Rate
PHY
PID
Physical Layer
Product Identification
Phase-Locked Loop
PLL
POR
RC13M
RC64k
RFO
RFU
RTC
Power On or Reset
13 MHz Resistance-Capacitance Oscillator
64 kHz Resistance-Capacitance Oscillator
Radio Frequency Output
Reserved for Future Use
Real-Time Clock
SCK
Serial Clock
SF
Spreading Factor
SN
Sequence Number
SNR
SPI
Signal to Noise Ratio
Serial Peripheral Interface
Single Side Bandwidth
Standby
SSB
STDBY
SX1261/2
Data Sheet
105 of 107
Semtech
www.semtech.com
Rev. 1.1
DS.SX1261-2.W.APP
December 2017
List of Acronyms and their Meaning
Acronym
Meaning
TCXO
XOSC
Temperature-Compensated Crystal Oscillator
Crystal Oscillator
SX1261/2
Data Sheet
106 of 107
Semtech
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Rev. 1.1
DS.SX1261-2.W.APP
December 2017
Important Notice
Information relating to this product and the application or design described herein is believed to be reliable, however such information
is provided as a guide only and Semtech assumes no liability for any errors in this document, or for the application or design described
herein. Semtech reserves the right to make changes to the product or this document at any time without notice. Buyers should obtain the
latest relevant information before placing orders and should verify that such information is current and complete. Semtech warrants
performance of its products to the specifications applicable at the time of sale, and all sales are made in accordance with Semtech’s
standard terms and conditions of sale.
SEMTECH PRODUCTS ARE NOT DESIGNED, INTENDED, AUTHORIZED OR WARRANTED TO BE SUITABLE FOR USE IN LIFE-SUPPORT
APPLICATIONS, DEVICES OR SYSTEMS, OR IN NUCLEAR APPLICATIONS IN WHICH THE FAILURE COULD BE REASONABLY EXPECTED TO
RESULT IN PERSONAL INJURY, LOSS OF LIFE OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE. INCLUSION OF SEMTECH PRODUCTS IN
SUCH APPLICATIONS IS UNDERSTOOD TO BE UNDERTAKEN SOLELY AT THE CUSTOMER’S OWN RISK. Should a customer purchase or use
Semtech products for any such unauthorized application, the customer shall indemnify and hold Semtech and its officers, employees,
subsidiaries, affiliates, and distributors harmless against all claims, costs damages and attorney fees which could arise.
The Semtech name and logo are registered trademarks of the Semtech Corporation. The LoRa® Mark is a registered trademark of the
Semtech Corporation. All other trademarks and trade names mentioned may be marks and names of Semtech or their respective
companies. Semtech reserves the right to make changes to, or discontinue any products described in this document without further
notice. Semtech makes no warranty, representation or guarantee, express or implied, regarding the suitability of its products for any
particular purpose. All rights reserved.
© Semtech 2017
Contact Information
Semtech Corporation
Wireless & Sensing Products
200 Flynn Road, Camarillo, CA 93012
Phone: (805) 498-2111, Fax: (805) 498-3804
www.semtech.com
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