SX1278IMLTRT - Semtech - Datasheet.Live

SX1276/77/78/79

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WIRELESS, SENSING & TIMING DATASHEET

SX1276/77/78/79 - 137 MHz to 1020 MHz Low Power Long Range Transceiver

Rev. 4 - March 2015

The SX1276/77/78/79 transceivers feature the LoRaTM long

range modem that provides ultra-long range spread

spectrum communication and high interference immunity

whilst minimising current consumption.

Using Semtech’s patented LoRaTM modulation technique

SX1276/77/78/79 can achieve a sensitivity of over -148dBm

using a low cost crystal and bill of materials. The high

sensitivity combined with the integrated +20 dBm power

amplifier yields industry leading link budget making it

optimal for any application requiring range or robustness.

LoRaTM also provides significant advantages in both

blocking and selectivity over conventional modulation

techniques, solving the traditional design compromise

between range, interference immunity and energy

consumption.

These devices also support high performance (G)FSK

modes for systems including WMBus, IEEE802.15.4g. The

SX1276/77/78/79 deliver exceptional phase noise,

selectivity, receiver linearity and IIP3 for significantly lower

current consumption than competing devices.

QFN 28 Package - Operating Range [-40;+85°C]

Pb-free, Halogen free, RoHS/WEEE compliant product

LoRaTM Modem

168 dB maximum link budget

+20 dBm - 100 mW constant RF output vs. V supply

+14 dBm high efficiency PA

Programmable bit rate up to 300 kbps

High sensitivity: down to -148 dBm

Bullet-proof front end: IIP3 = -11 dBm

Excellent blocking immunity

Low RX current of 9.9 mA, 200 nA register retention

Fully integrated synthesizer with a resolution of 61 Hz

FSK, GFSK, MSK, GMSK, LoRaTMand OOK modulation

Built-in bit synchronizer for clock recovery

Preamble detection

127 dB Dynamic Range RSSI

Automatic RF Sense and CAD with ultra-fast AFC

Packet engine up to 256 bytes with CRC

Built-in temperature sensor and low battery indicator

Automated Meter Reading.

Home and Building Automation.

Wireless Alarm and Security Systems.

Industrial Monitoring and Control

Long range Irrigation Systems

GENERAL DESCRIPTION

ORDERING INFORMATION

Part Number Delivery MOQ / Multiple

SX1276IMLTRT T&R 3000 pieces

SX1277IMLTRT T&R 3000 pieces

SX1278IMLTRT T&R 3000 pieces

SX1279IMLTRT T&R 3000 pieces

KEY PRODUCT FEATURES

APPLICATIONS

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Section Page
Table of contents
SX1276/77/78/79
WIRELESS, SENSING & TIMING  DATASHEET
Rev. 4 - March 2015
©2015 Semtech Corporation
  General Description ................................................................................................................................................. 9
1.   Simplified Block Diagram ................................................................................................................................. 9
2.   Product Versions ............................................................................................................................................10
3.   Pin Diagram ................................................................................................................................................... 10
4.   Pin Description ...............................................................................................................................................11
5.  Package Marking ...........................................................................................................................................12
  Electrical Characteristics ....................................................................................................................................... 13
1.   ESD Notice .................................................................................................................................................... 13
2.   Absolute Maximum Ratings ........................................................................................................................... 13
3.   Operating Range............................................................................................................................................ 13
4.   Thermal Properties ........................................................................................................................................ 13
5.   Chip Specification  ..........................................................................................................................................14
5.1.  Power Consumption .................................................................................................................................. 14
5.2.  Frequency Synthesis................................................................................................................................. 14
5.3.  FSK/OOK Mode Receiver  .........................................................................................................................16
5.4.  FSK/OOK Mode Transmitter ..................................................................................................................... 17
5.5.  Electrical Specification for LoRaTM Modulation ........................................................................................19
5.6.  Digital Specification  ...................................................................................................................................22
 SX1276/77/78/79 Features.................................................................................................................................... 23
1.   LoRaTM Modem ............................................................................................................................................ 24
2.   FSK/OOK Modem .......................................................................................................................................... 24
  SX1276/77/78/79 Digital Electronics ..................................................................................................................... 25
1.   The LoRaTM Modem ..................................................................................................................................... 25
1.1.  Link Design Using the LoRaTM Modem ....................................................................................................26
1.2.  LoRaTM Digital Interface ...........................................................................................................................34
1.3.  Operation of the LoRaTM Modem............................................................................................................. 36
1.4.  Frequency Settings  ...................................................................................................................................37
1.5.  Frequency Error Indication ........................................................................................................................ 37
1.6.  LoRaTM Modem State Machine Sequences .............................................................................................38
1.7.  Modem Status Indicators........................................................................................................................... 46
2.   FSK/OOK Modem .......................................................................................................................................... 46
2.1.  Bit Rate Setting ......................................................................................................................................... 46
2.2.  FSK/OOK Transmission ............................................................................................................................ 47
2.3.  FSK/OOK Reception ................................................................................................................................. 48
2.4.  Operating Modes in FSK/OOK Mode ........................................................................................................ 54
2.5.  Startup Times  ............................................................................................................................................56
2.6.  Receiver Startup Options .......................................................................................................................... 59
2.7.  Receiver Restart Methods......................................................................................................................... 60
2.8.  Top Level Sequencer ................................................................................................................................ 61

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Table of contents
SX1276/77/78/79
WIRELESS, SENSING & TIMING  DATASHEET
Rev. 4 - March 2015
©2015 Semtech Corporation
2.9.  Data Processing in FSK/OOK Mode ......................................................................................................... 65
2.10.  FIFO  ........................................................................................................................................................66
2.11.  Digital IO Pins Mapping ...........................................................................................................................69
2.12.  Continuous Mode  ....................................................................................................................................70
2.13.  Packet Mode ........................................................................................................................................... 71
2.14.  io-homecontrol® Compatibility Mode ...................................................................................................... 79
3.   SPI Interface  ..................................................................................................................................................80
  SX1276/77/78/79 Analog & RF Frontend Electronics............................................................................................ 81
1.   Power Supply Strategy .................................................................................................................................. 81
2.   Low Battery Detector ..................................................................................................................................... 81
3.   Frequency Synthesis ..................................................................................................................................... 81
3.1.  Crystal Oscillator ....................................................................................................................................... 81
3.2.  CLKOUT Output ........................................................................................................................................ 82
3.3.  PLL ............................................................................................................................................................ 82
3.4.  RC Oscillator ............................................................................................................................................. 82
4.  Transmitter Description ..................................................................................................................................83
4.1.  Architecture Description ............................................................................................................................ 83
4.2.  RF Power Amplifiers.................................................................................................................................. 83
4.3.  High Power +20 dBm Operation ............................................................................................................... 84
4.4.  Over Current Protection  ............................................................................................................................85
5.  Receiver Description...................................................................................................................................... 85
5.1.  Overview ................................................................................................................................................... 85
5.2.  Receiver Enabled and Receiver Active States.......................................................................................... 85
5.3.  Automatic Gain Control In FSK/OOK Mode .............................................................................................. 85
5.4.  RSSI in FSK/OOK Mode ........................................................................................................................... 86
5.5.  RSSI and SNR in LoRaTM Mode.............................................................................................................. 87
5.6.  Channel Filter ............................................................................................................................................ 88
5.7.  Temperature Measurement....................................................................................................................... 89
  Description of the Registers................................................................................................................................... 90
1.   Register Table Summary ............................................................................................................................... 90
2.   FSK/OOK Mode Register Map .......................................................................................................................93
3.   Band Specific Additional Registers .............................................................................................................. 106
4.   LoRaTM Mode Register Map....................................................................................................................... 108
  Application Information ........................................................................................................................................ 115
1.   Crystal Resonator Specification................................................................................................................... 115
2.   Reset of the Chip ......................................................................................................................................... 115
2.1.  POR......................................................................................................................................................... 115
2.2.  Manual Reset  ..........................................................................................................................................116
3.   Top Sequencer: Listen Mode Examples ...................................................................................................... 116

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Table of contents
SX1276/77/78/79
WIRELESS, SENSING & TIMING  DATASHEET
Rev. 4 - March 2015
©2015 Semtech Corporation
7.3.1.  Wake on Preamble Interrupt ................................................................................................................... 116
7.3.2.  Wake on SyncAddress Interrupt ..............................................................................................................119
7.4.   Top Sequencer: Beacon Mode  ....................................................................................................................122
7.4.1.  Timing diagram........................................................................................................................................ 122
7.4.2.  Sequencer Configuration......................................................................................................................... 122
7.5.   Example CRC Calculation  ...........................................................................................................................124
7.6.   Example Temperature Reading  ...................................................................................................................125
8.   Packaging Information ......................................................................................................................................... 127
8.1.   Package Outline Drawing ............................................................................................................................ 127
8.2.   Recommended Land Pattern ....................................................................................................................... 128
8.3.   Tape & Reel Information .............................................................................................................................. 129
9.   Revision History................................................................................................................................................... 130

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Section Page
Table of contents
SX1276/77/78/79
WIRELESS, SENSING & TIMING  DATASHEET
Rev. 4 - March 2015
©2015 Semtech Corporation
Table 1.  SX1276/77/78/79 Device Variants and Key Parameters .................................................................................10
Table 2.  Pin Description  ................................................................................................................................................11
Table 3.  Absolute Maximum Ratings .............................................................................................................................13
Table 4.  Operating Range  .............................................................................................................................................13
Table 5.  Thermal Properties  ..........................................................................................................................................13
Table 6.  Power Consumption Specification ...................................................................................................................14
Table 7.  Frequency Synthesizer Specification  ..............................................................................................................14
Table 8.  FSK/OOK Receiver Specification  ....................................................................................................................16
Table 9.  Transmitter Specification .................................................................................................................................17
Table 10.  LoRa Receiver Specification .........................................................................................................................19
Table 11.  Digital Specification  .......................................................................................................................................22
Table 12.  Example LoRaTM Modem Performances, 868MHz Band .............................................................................25
Table 13.  Range of Spreading Factors ..........................................................................................................................27
Table 14.  Cyclic Coding Overhead ................................................................................................................................27
Table 15.  LoRa Bandwidth Options ...............................................................................................................................28
Table 16.  LoRaTM Operating Mode Functionality .........................................................................................................36
Table 17.  LoRa CAD Consumption Figures  ..................................................................................................................45
Table 18.  DIO Mapping LoRaTM Mode .........................................................................................................................46
Table 19.  Bit Rate Examples  .........................................................................................................................................47
Table 20.  Preamble Detector Settings ...........................................................................................................................53
Table 21.  RxTrigger Settings to Enable Timeout Interrupts ..........................................................................................54
Table 22.  Basic Transceiver Modes  ..............................................................................................................................54
Table 23.  Receiver Startup Time Summary  ..................................................................................................................57
Table 24.  Receiver Startup Options ..............................................................................................................................60
Table 25.  Sequencer States ..........................................................................................................................................61
Table 26.  Sequencer Transition Options  .......................................................................................................................62
Table 27.  Sequencer Timer Settings  .............................................................................................................................63
Table 28.  Status of FIFO when Switching Between Different Modes of the Chip  .........................................................67
Table 29.  DIO Mapping, Continuous Mode  ...................................................................................................................69
Table 30.  DIO Mapping, Packet Mode ..........................................................................................................................69
Table 31.   CRC Description ...........................................................................................................................................77
Table 32.  Frequency Bands  ..........................................................................................................................................82
Table 33.  Power Amplifier Mode Selection Truth Table  ................................................................................................83
Table 34.  High Power Settings  ......................................................................................................................................84
Table 35.  Operating Range, +20dBm Operation  ...........................................................................................................84
Table 36.  Operating Range, +20dBm Operation  ...........................................................................................................84
Table 37.  Trimming of the OCP Current ........................................................................................................................85
Table 38.  LNA Gain Control and Performances  ............................................................................................................86
Table 39.  RssiSmoothing Options .................................................................................................................................86

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Table of contents
SX1276/77/78/79
WIRELESS, SENSING & TIMING  DATASHEET
Rev. 4 - March 2015
©2015 Semtech Corporation
Table 40.  Available RxBw Settings ................................................................................................................................88
Table 41.  Registers Summary  .......................................................................................................................................90
Table 42.  Register Map  .................................................................................................................................................93
Table 43.  Low Frequency Additional Registers  ...........................................................................................................106
Table 44.  High Frequency Additional Registers  ..........................................................................................................107
Table 45.  Crystal Specification  ....................................................................................................................................115
Table 46.  Listen Mode with PreambleDetect Condition Settings .................................................................................118
Table 47.  Listen Mode with PreambleDetect Condition Recommended DIO Mapping  ...............................................118
Table 48.  Listen Mode with SyncAddress Condition Settings  .....................................................................................121
Table 49.  Listen Mode with PreambleDetect Condition Recommended DIO Mapping  ...............................................121
Table 50.  Beacon Mode Settings  ................................................................................................................................123
Table 51.  Revision History ...........................................................................................................................................130

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Table of contents
SX1276/77/78/79
WIRELESS, SENSING & TIMING  DATASHEET
Rev. 4 - March 2015
©2015 Semtech Corporation
Figure 1.   Block Diagram  .................................................................................................................................................9
Figure 2.   Pin Diagrams .................................................................................................................................................10
Figure 3.   Marking Diagram  ...........................................................................................................................................12
Figure 4.   SX1276/77/78/79 Block Schematic Diagram ................................................................................................23
Figure 5.   LoRaTM Modem Connectivity  .......................................................................................................................26
Figure 6.   LoRaTM Packet Structure .............................................................................................................................29
Figure 7.   Interrupts Generated in the Case of Successful Frequency Hopping Communication.  ................................33
Figure 8.   LoRaTM Data Buffer .....................................................................................................................................34
Figure 9.   LoRaTM Modulation Transmission Sequence.  .............................................................................................38
Figure 10.   LoRaTM Receive Sequence.  ......................................................................................................................39
Figure 11.   LoRaTM CAD Flow  .....................................................................................................................................43
Figure 12.   CAD Time as a Function of Spreading Factor .............................................................................................44
Figure 13.   Consumption Profile of the LoRa CAD Process ..........................................................................................45
Figure 14.   OOK Peak Demodulator Description ...........................................................................................................49
Figure 15.   Floor Threshold Optimization ......................................................................................................................50
Figure 16.   Bit Synchronizer Description .......................................................................................................................51
Figure 17.   Startup Process ...........................................................................................................................................56
Figure 18.   Time to RSSI Sample ..................................................................................................................................57
Figure 19.   Tx to Rx Turnaround ...................................................................................................................................58
Figure 20.   Rx to Tx Turnaround  ...................................................................................................................................58
Figure 21.   Receiver Hopping ........................................................................................................................................59
Figure 22.   Transmitter Hopping ....................................................................................................................................59
Figure 23.   Timer1 and Timer2 Mechanism ...................................................................................................................63
Figure 24.   Sequencer State Machine  ...........................................................................................................................64
Figure 25.   SX1276/77/78/79 Data Processing Conceptual View  .................................................................................65
Figure 26.   FIFO and Shift Register (SR)  ......................................................................................................................66
Figure 27.   FifoLevel IRQ Source Behavior ...................................................................................................................67
Figure 28.   Sync Word Recognition ...............................................................................................................................68
Figure 29.   Continuous Mode Conceptual View  ............................................................................................................70
Figure 30.   Tx Processing in Continuous Mode .............................................................................................................70
Figure 31.   Rx Processing in Continuous Mode  ............................................................................................................71
Figure 32.   Packet Mode Conceptual View  ...................................................................................................................72
Figure 33.   Fixed Length Packet Format  .......................................................................................................................73
Figure 34.   Variable Length Packet Format ...................................................................................................................74
Figure 35.   Unlimited Length Packet Format  .................................................................................................................74
Figure 36.   Manchester Encoding/Decoding .................................................................................................................78
Figure 37.   Data Whitening Polynomial .........................................................................................................................79
Figure 38.   SPI Timing Diagram (single access)  ...........................................................................................................80
Figure 39.   TCXO Connection  .......................................................................................................................................81

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Table of contents
SX1276/77/78/79
WIRELESS, SENSING & TIMING  DATASHEET
Rev. 4 - March 2015
©2015 Semtech Corporation
Figure 40.   RF Front-end Architecture Shows the Internal PA Configuration. ...............................................................83
Figure 41.   Temperature Sensor Response  ..................................................................................................................89
Figure 42.   POR Timing Diagram  ................................................................................................................................115
Figure 43.   Manual Reset Timing Diagram ..................................................................................................................116
Figure 44.   Listen Mode: Principle ...............................................................................................................................116
Figure 45.   Listen Mode with No Preamble Received  .................................................................................................117
Figure 46.   Listen Mode with Preamble Received  .......................................................................................................117
Figure 47.   Wake On PreambleDetect State Machine .................................................................................................118
Figure 48.   Listen Mode with no SyncAddress Detected .............................................................................................119
Figure 49.   Listen Mode with Preamble Received and no SyncAddress .....................................................................119
Figure 50.   Listen Mode with Preamble Received & Valid SyncAddress  ....................................................................120
Figure 51.   Wake On SyncAddress State Machine  .....................................................................................................120
Figure 52.   Beacon Mode Timing Diagram ..................................................................................................................122
Figure 53.   Beacon Mode State Machine  ....................................................................................................................122
Figure 54.   Example CRC Code  ..................................................................................................................................124
Figure 55.   Example Temperature Reading  ................................................................................................................125
Figure 56.   Example Temperature Reading (continued)  .............................................................................................126
Figure 57.   Package Outline Drawing ..........................................................................................................................127
Figure 58.   Recommended Land Pattern ....................................................................................................................128
Figure 59.   Tape and Reel Information ........................................................................................................................129

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1. General Description

The SX1276/77/78/79 incorporates the LoRaTM spread spectrum modem which is capable of achieving significantly longer

range than existing systems based on FSK or OOK modulation. At maximum data rates of LoRaTM the sensitivity is 8dB

better than FSK, but using a low cost bill of materials with a 20ppm XTAL LoRaTM can improve receiver sensitivity by more

than 20dB compared to FSK. LoRaTM also provides significant advances in selectivity and blocking performance, further

improving communication reliability. For maximum flexibility the user may decide on the spread spectrum modulation

bandwidth (BW), spreading factor (SF) and error correction rate (CR). Another benefit of the spread modulation is that

each spreading factor is orthogonal - thus multiple transmitted signals can occupy the same channel without interfering.

This also permits simple coexistence with existing FSK based systems. Standard GFSK, FSK, OOK, and GMSK

modulation is also provided to allow compatibility with existing systems or standards such as wireless MBUS and IEEE

802.15.4g.

The SX1276 and SX1279 offer bandwidth options ranging from 7.8 kHz to 500 kHz with spreading factors ranging from 6 to

12, and covering all available frequency bands. The SX1277 offers the same bandwidth and frequency band options with

spreading factors from 6 to 9. The SX1278 offers bandwidths and spreading factor options, but only covers the lower UHF

bands.

1.1. Simplified Block Diagram

Figure 1. Block Diagram

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1.2. Product Versions

The features of the four product variants are detailed in the following table.

Table 1 SX1276/77/78/79 Device Variants and Key Parameters

1.3. Pin Diagram

The following diagram shows the pin arrangement of the QFN package, top view.

Figure 2. Pin Diagrams

Part Number Frequency Range Spreading Factor Bandwidth Effective Bitrate Est. Sensitivity

SX1276 137 - 1020 MHz 6 - 12 7.8 - 500 kHz .018 - 37.5 kbps -111 to -148 dBm

SX1277 137 - 1020 MHz 6 - 9 7.8 - 500 kHz 0.11 - 37.5 kbps -111 to -139 dBm

SX1278 137 - 525 MHz 6- 12 7.8 - 500 kHz .018 - 37.5 kbps -111 to -148 dBm

SX1279 137 - 960MHz 6- 12 7.8 - 500 kHz .018 - 37.5 kbps -111 to -148 dBm

1 RFI_LF

3 VBAT_ANA

4 VR_DIG

5 XTA

6 XTB

7 NRESET

8 DIO0

9 DIO1

10 DIO2

11 DIO3

12 DIO4

13 DIO5

14 VBAT_DIG

21 RFI_HF

20 RXTX/RFMOD

19 NSS

18 MOSI

17 MISO

16 SCK

15 GND

25 VR_PA

27 PA_BOOST

26 GND

28 RFO_LF

23 GND

0 GND

SX1276/77/79 SX1278

2 VR_ANA

24 VBAT_RF

22 RFO_HF

1 RFI_LF

3 VBAT_ANA

4 VR_DIG

5 XTA

6 XTB

7 NRESET

8 DIO0

9 DIO1

10 DIO2

11 DIO3

12 DIO4

13 DIO5

14 VBAT_DIG

21 GND

20 RXTX/RFMOD

19 NSS

18 MOSI

17 MISO

16 SCK

15 GND

25 VR_PA

27 PA_BOOST

26 GND

28 RFO_LF

23 GND

0 GND

2 VR_ANA

24 VBAT_RF

22 GND

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1.4. Pin Description

Table 2 Pin Description

Number Name Type Description

SX1276/77/79/(78) SX1276/77/79/(78) SX1276/77/79/(78)

0 GROUND -Exposed ground pad

1 RFI_LF IRF input for bands 2&3

2VR_ANA -Regulated supply voltage for analogue circuitry

3 VBAT_ANA -Supply voltage for analogue circuitry

4 VR_DIG -Regulated supply voltage for digital blocks

5XTA I/O XTAL connection or TCXO input

6XTB I/O XTAL connection

7 NRESET I/O Reset trigger input

8DIO0 I/O Digital I/O, software configured

9 DIO1/DCLK I/O Digital I/O, software configured

10 DIO2/DATA I/O Digital I/O, software configured

11 DIO3 I/O Digital I/O, software configured

12 DIO4 I/O Digital I/O, software configured

13 DIO5 I/O Digital I/O, software configured

14 VBAT_DIG -Supply voltage for digital blocks

15 GND -Ground

16 SCK ISPI Clock input

17 MISO OSPI Data output

18 MOSI ISPI Data input

19 NSS ISPI Chip select input

20 RXTX/RF_MOD ORx/Tx switch control: high in Tx

21 RFI_HF (GND) I (-) RF input for band 1 (Ground)

22 RFO_HF (GND) O (-) RF output for band 1 (Ground)

23 GND -Ground

24 VBAT_RF -Supply voltage for RF blocks

25 VR_PA -Regulated supply for the PA

26 GND -Ground

27 PA_BOOST OOptional high-power PA output, all frequency bands

28 RFO_LF ORF output for bands 2&3

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1.5. Package Marking

Figure 3. Marking Diagram

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2. Electrical Characteristics

2.1. ESD Notice

The SX1276/77/78/79 is a high performance radio frequency device. It satisfies:

Class 2 of the JEDEC standard JESD22-A114 (Human Body Model) on all pins.

Class III of the JEDEC standard JESD22-C101 (Charged Device Model) on all pins

It should thus be handled with all the necessary ESD precautions to avoid any permanent damage.

2.2. 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.

Table 3 Absolute Maximum Ratings

Note Specific ratings apply to +20 dBm operation (see Section 5.4.3).

2.3. Operating Range

Table 4 Operating Range

Note A specific supply voltage range applies to +20 dBm operation (see Section 5.4.3).

2.4. Thermal Properties

Table 5 Thermal Properties

Symbol Description Min Max Unit

VDDmr Supply Voltage -0.5 3.9 V

Tmr Temperature -55 +115 ° C

Tj Junction temperature -+125 ° C

Pmr RF Input Level -+10 dBm

Symbol Description Min Max Unit

VDDop Supply voltage 1.8 3.7 V

Top Operational temperature range -40 +85 °C

Clop Load capacitance on digital ports -25 pF

ML RF Input Level -+10 dBm

Symbol Description Min Typ Max Unit

THETA_JA Package

ja (Junction to ambient) -22.185 -°C/W

THETA_JC Package

jc (Junction to case ground paddle) -0.757 -°C/W

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2.5. Chip Specification

The tables below give the electrical specifications of the transceiver under the following conditions: Supply voltage

VDD=3.3 V, temperature = 25 °C, FXOSC = 32 MHz, FRF = 169/434/868/915 MHz (see specific indication), Pout =

+13dBm, 2-level FSK modulation without pre-filtering, FDA = 5 kHz, Bit Rate = 4.8 kb/s and terminated in a matched 50

Ohm impedance, shared Rx and Tx path matching, unless otherwise specified.

Note Specification whose symbol is appended with “_LF” corresponds to the performance in Band 2 and/or Band 3, as

described in section 5.3.3. “_HF” refers to the upper Band 1

2.5.1. Power Consumption

Table 6 Power Consumption Specification

2.5.2. Frequency Synthesis

Table 7 Frequency Synthesizer Specification

Symbol Description Conditions Min Typ Max Unit

IDDSL Supply current in Sleep mode -0.2 1uA

IDDIDLE Supply current in Idle mode RC oscillator enabled -1.5 -uA

IDDST Supply current in Standby mode Crystal oscillator enabled -1.6 1.8 mA

IDDFS Supply current in Synthesizer

mode FSRx -5.8 -mA

IDDR Supply current in Receive mode

LnaBoost Off, band 1

LnaBoost On, band 1

Bands 2&3

10.8

11.5

12.0

IDDT Supply current in Transmit mode

with impedance matching

RFOP = +20 dBm, on PA_BOOST

RFOP = +17 dBm, on PA_BOOST

RFOP = +13 dBm, on RFO_LF/HF pin

RFOP = + 7 dBm, on RFO_LF/HF pin

120

Symbol Description Conditions Min Typ Max Unit

FR Synthesizer frequency range

Band 3

Programmable Band 2

(*for SX1279) Band 1

137

410

862 (*779)

175 (*160)

525 (*480)

1020 (*960)

MHz

FXOSC Crystal oscillator frequency -32 -MHz

TS_OSC Crystal oscillator wake-up time -250 -us

TS_FS Frequency synthesizer wake-up

time to PllLock signal From Standby mode -60 -us

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Note: For Maximum Bit rate, the maximum modulation index is 0.5.

TS_HOP

Frequency synthesizer hop time

at most 10 kHz away from the

target frequency

200 kHz step

1 MHz step

5 MHz step

7 MHz step

12 MHz step

20 MHz step

25 MHz step

FSTEP Frequency synthesizer step FSTEP = FXOSC/219 -61.0 -Hz

FRC RC Oscillator frequency After calibration -62.5 -kHz

BRF Bit rate, FSK Programmable values (1) 1.2 -300 kbps

BRA Bit rate Accuracy, FSK ABS(wanted BR - available BR) - - 250 ppm

BRO Bit rate, OOK Programmable 1.2 -32.768 kbps

BR_L Bit rate, LoRa Mode From SF6, BW=500kHz to

SF12, BW=7.8kHz

0.018 -37.5 kbps

FDA Frequency deviation, FSK (1) Programmable

FDA + BRF/2 =< 250 kHz

0.6 -200 kHz

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2.5.3. FSK/OOK Mode Receiver

All receiver tests are performed with RxBw = 10 kHz (Single Side Bandwidth) as programmed in RegRxBw, receiving a

PN15 sequence. Sensitivities are reported for a 0.1% BER (with Bit Synchronizer enabled), unless otherwise specified.

Blocking tests are performed with an unmodulated interferer. The wanted signal power for the Blocking Immunity, ACR,

IIP2, IIP3 and AMR tests is set 3 dB above the receiver sensitivity level.

Table 8 FSK/OOK Receiver Specification

Symbol Description Conditions Min Typ Max Unit

RFS_F_LF

Direct tie of RFI and RFO pins,

shared Rx, Tx paths FSK sensitiv-

ity, highest LNA gain.

Bands 2&3

FDA = 5 kHz, BR = 1.2 kb/s

FDA = 5 kHz, BR = 4.8 kb/s

FDA = 40 kHz, BR = 38.4 kb/s*

FDA = 20 kHz, BR = 38.4 kb/s**

FDA = 62.5 kHz, BR = 250 kb/s***

-121

-117

-107

-108

-95

dBm

Split RF paths, the RF switch

insertion loss is not accounted for.

Bands 2&3

FDA = 5 kHz, BR = 1.2 kb/s

FDA = 5 kHz, BR = 4.8 kb/s

FDA = 40 kHz, BR = 38.4 kb/s*

FDA = 20 kHz, BR = 38.4 kb/s**

FDA = 62.5 kHz, BR = 250 kb/s***

-123

-119

-109

-110

-97

dBm

RFS_F_HF

Direct tie of RFI and RFO pins,

shared Rx, Tx paths FSK sensitiv-

ity, highest LNA gain.

Band 1

FDA = 5 kHz, BR = 1.2 kb/s

FDA = 5 kHz, BR = 4.8 kb/s

FDA = 40 kHz, BR = 38.4 kb/s*

FDA = 20 kHz, BR = 38.4 kb/s**

FDA = 62.5 kHz, BR = 250 kb/s***

-119

-115

-105

-92

dBm

Split RF paths, LnaBoost is turned

on, the RF switch insertion loss is

not accounted for.

Band 1

FDA = 5 kHz, BR = 1.2 kb/s

FDA = 5 kHz, BR = 4.8 kb/s

FDA = 40 kHz, BR = 38.4 kb/s*

FDA = 20 kHz, BR = 38.4 kb/s**

FDA = 62.5 kHz, BR = 250 kb/s***

-123

-119

-109

-96

dBm

RFS_O OOK sensitivity, highest LNA gain

shared Rx, Tx paths

BR = 4.8 kb/s

BR = 32 kb/s

-117

-108

dBm

CCR Co-Channel Rejection, FSK --9 -dB

ACR Adjacent Channel Rejection

FDA = 5 kHz, BR=4.8kb/s

Offset = +/- 25 kHz or +/- 50kHz

Band 1

Band 2

Band 3

BI_HF Blocking Immunity, Band 1

Offset = +/- 1 MHz

Offset = +/- 2 MHz

Offset = +/- 10 MHz

BI_LF Blocking Immunity, Bands 2&3

Offset = +/- 1 MHz

Offset = +/- 2 MHz

Offset = +/- 10 MHz

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* RxBw = 83 kHz (Single Side Bandwidth)

** RxBw = 50 kHz (Single Side Bandwidth)

*** RxBw = 250 kHz (Single Side Bandwidth)

2.5.4. FSK/OOK Mode Transmitter

Table 9 Transmitter Specification

IIP2

2nd order Input Intercept Point

Unwanted tones are 20 MHz

above the LO

Highest LNA gain -+55 -dBm

IIP3_HF

3rd order Input Intercept point

Unwanted tones are 1MHz and

1.995 MHz above the LO

Band 1

Highest LNA gain G1

LNA gain G2, 5dB sensitivity hit

-11

-6

dBm

IIP3_LF

3rd order Input Intercept point

Unwanted tones are 1MHz and

1.995 MHz above the LO

Band 2

Highest LNA gain G1

LNA gain G2, 2.5dB sensitivity hit

-22

-15

dBm

Band 3

Highest LNA gain G1

LNA gain G2, 2.5dB sensitivity hit

-15

-11

dBm

BW_SSB Single Side channel filter BW Programmable 2.7 -250 kHz

IMR Image Rejection Wanted signal 3dB over sensitivity

BER=0.1% -50 -dB

IMA Image Attenuation -57 -dB

DR_RSSI RSSI Dynamic Range AGC enabled Min

Max

-127

dBm

Symbol Description Conditions Min Typ Max Unit

RF_OP RF output power in 50 ohms

on RFO pin (High efficiency PA).

Programmable with steps

Max

Min

+14

-1

dBm

ΔRF_

OP_V

RF output power stability on RFO

pin versus voltage supply.

VDD = 2.5 V to 3.3 V

VDD = 1.8 V to 3.7 V

RF_OPH RF output power in 50 ohms, on

PA_BOOST pin (Regulated PA).

Programmable with 1dB steps Max

Min

+17

dBm

RF_OPH_

MAX

Max RF output power, on

PA_BOOST pin High power mode -+20 -dBm

ΔRF_

OPH_V

RF output power stability on PA_-

BOOST pin versus voltage supply. VDD = 2.4 V to 3.7 V -+/-1 -dB

ΔRF_T RF output power stability versus

temperature on PA_BOOST pin. From T = -40 °C to +85 °C -+/-1 -dB

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PHN Transmitter Phase Noise

169 MHz, Band 3

10kHz Offset

50kHz Offset

400kHz Offset

1MHz Offset

-118

-128

-134

dBc/

433 MHz, Band 2

10kHz Offset

50kHz Offset

400kHz Offset

1MHz Offset

-110

-122

-129

dBc/

868/915 MHz, Band 1

10kHz Offset

50kHz Offset

400kHz Offset

1MHz Offset

-103

-115

-122

dBc/

ACP Transmitter adjacent channel

power (measured at 25 kHz offset)

BT=1. Measurement conditions as

defined by EN 300 220-1 V2.3.1 - - -37 dBm

TS_TR Transmitter wake up time, to the

first rising edge of DCLK

Frequency Synthesizer enabled, PaR-

amp = 10us, BR = 4.8 kb/s -120 -us

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2.5.5. Electrical Specification for LoRaTM Modulation

The table below gives the electrical specifications for the transceiver operating with LoRaTM modulation. Following

conditions apply unless otherwise specified:

Supply voltage = 3.3 V

Temperature = 25° C

fXOSC = 32 MHz

bandwidth (BW) = 125 kHz

Spreading Factor (SF) = 12

Error Correction Code (EC) = 4/6

Packet Error Rate (PER)= 1%

CRC on payload enabled

Output power = 13 dBm in transmission

Payload length = 64 bytes

Preamble Length = 12 symbols (programmed register PreambleLength=8)

With matched impedances

Table 10 LoRa Receiver Specification

Symbol Description Conditions Min. Typ Max Unit

IDDR_L Supply current in receiver LoRaTM

mode, LnaBoost off

Bands 2&3, BW=7.8 to 62.5 kHz

Bands 2&3, BW = 125 kHz

Bands 2&3, BW = 250 kHz

Bands 2&3, BW = 500 kHz

11.0

11.5

12.4

13.8

Band 1, BW=7.8 to 62.5 kHz

Band 1, BW = 125 kHz

Band 1, BW = 250 kHz

Band 1, BW = 500 kHz

9.9

10.3

11.1

12.6

IDDT_L Supply current in transmitter mode RFOP = 13 dBm

RFOP = 7 dBm

IDDT_H_L

Supply current in transmitter mode

with an external impedance

transformation

Using PA_BOOST pin

RFOP = 17 dBm -90-mA

BI_L Blocking immunity,

CW interferer

offset = +/- 1 MHz

offset = +/- 2 MHz

offset = +/- 10 MHz

100

IIP2_L

2nd order Input Intercept Point

Unwanted tones are 20 MHz above

the LO

Highest LNA gain -+55 -dBm

IIP3_L_HF

3rd order Input Intercept point

Unwanted tones are 1MHz and 1.995

MHz above the LO

Band 1

Highest LNA gain G1

LNA gain G2, 5dB sensitivity hit

-11

-6

dBm

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IIP3_L_LF

3rd order Input Intercept point

Unwanted tones are 1MHz and 1.995

MHz above the LO

Band 2

Highest LNA gain G1

LNA gain G2,2.5dB sensitivity hit

-22

-15

dBm

RFS_L10_HF

RF sensitivity, Long-Range Mode,

highest LNA gain, LnaBoost for Band

1, using split Rx/Tx path

10.4 kHz bandwidth

SF = 6

SF = 7

SF = 8

SF = 11

-131

-134

-138

-146

dBm

RFS_L62_HF

RF sensitivity, Long-Range Mode,

highest LNA gain, LnaBoost for Band

1, using split Rx/Tx path

62.5 kHz bandwidth

SF = 6

SF = 7

SF = 8

SF = 9

SF = 10

SF = 11

SF = 12

-121

-126

-129

-132

-135

-137

-139

dBm

RFS_L125_HF

RF sensitivity, Long-Range Mode,

highest LNA gain, LnaBoost for Band

1, using split Rx/Tx path

125 kHz bandwidth

SF = 6

SF = 7

SF = 8

SF = 9

SF = 10

SF = 11

SF = 12

-118

-123

-126

-129

-132

-133

-136

dBm

RFS_L250_HF

RF sensitivity, Long-Range Mode,

highest LNA gain, LnaBoost for Band

1, using split Rx/Tx path

250 kHz bandwidth

SF = 6

SF = 7

SF = 8

SF = 9

SF = 10

SF = 11

SF = 12

-115

-120

-123

-125

-128

-130

-133

dBm

RFS_L500_HF

RF sensitivity, Long-Range Mode,

highest LNA gain, LnaBoost for Band

1, using split Rx/Tx path

500 kHz bandwidth

SF = 6

SF = 7

SF = 8

SF = 9

SF = 10

SF = 11

SF = 12

-111

-116

-119

-122

-125

-128

-130

dBm

RFS_L7.8_LF

RF sensitivity, Long-Range Mode,

highest LNA gain, Band 2 or 3, using

split Rx/Tx path

7.8 kHz bandwidth

SF = 12

SF = 11

-148

-145

dBm

RFS_L10_LF

RF sensitivity, Long-Range Mode,

highest LNA gain, Band 3,

10.4 kHz bandwidth

SF = 6

SF = 7

SF = 8

-132

-136

-138

dBm

RFS_L62_LF

RF sensitivity, Long-Range Mode,

highest LNA gain, Band 3,

62.5 kHz bandwidth

SF = 6

SF = 7

SF = 8

SF = 9

SF = 10

SF = 11

SF = 12

-123

-128

-131

-134

-135

-137

-140

dBm

Symbol Description Conditions Min. Typ Max Unit

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RFS_L125_LF

RF sensitivity, Long-Range Mode,

highest LNA gain, Band 3,

125 kHz bandwidth

SF = 6

SF = 7

SF = 8

SF = 9

SF = 10

SF = 11

SF = 12

-121

-125

-128

-131

-134

-136

-137

dBm

RFS_L250_LF

RF sensitivity, Long-Range Mode,

highest LNA gain, Band 3

250 kHz bandwidth

SF = 6

SF = 7

SF = 8

SF = 9

SF = 10

SF = 11

SF = 12

-118

-122

-125

-128

-131

-133

-134

dBm

RFS_L500_LF

RF sensitivity, Long-Range Mode,

highest LNA gain, Band 3

500 kHz bandwidth

SF = 6

SF = 7

SF = 8

SF = 9

SF = 10

SF = 11

SF = 12

-112

-118

-121

-124

-127

-129

-130

dBm

CCR_LCW

Co-channel rejection

Single CW tone = Sens +6 dB

1% PER

SF = 7

SF = 8

SF = 9

SF = 10

SF = 11

SF = 12

9.5

14.4

19.5

CCR_LL Co-channel rejection

Interferer is a LoRaTM signal

using same BW and same SF.

Pw = Sensitivity + 3 dB

-6

ACR_LCW Adjacent channel rejection

Interferer is 1.5*BW_L from the

wanted signal center frequency

1% PER, Single CW tone =

Sens + 3 dB

SF = 7

SF = 12

IMR_LCW Image rejection after calibration. 1% PER, Single CW tone =

Sens +3 dB -66-dB

FERR_L

Maximum tolerated frequency offset

between transmitter and receiver, no

sensitivity degradation, SF6 thru 12

All BW, +/-25% of BW

The tighter limit applies (see

below)

+/-25% BW

Maximum tolerated frequency offset

between transmitter and receiver, no

sensitivity degradation, SF10 thru 12

SF = 12

SF = 11

SF = 10

-50

-100

-200

100

200

ppm

Symbol Description Conditions Min. Typ Max Unit

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2.5.6. Digital Specification

Conditions: Temp = 25° C, VDD = 3.3 V, FXOSC = 32 MHz, unless otherwise specified.

Table 11 Digital Specification

Symbol Description Conditions Min Typ Max Unit

VIH Digital input level high 0.8 - - VDD

VIL Digital input level low - - 0.2 VDD

VOH Digital output level high Imax = 1 mA 0.9 - - VDD

VOL Digital output level low Imax = -1 mA - - 0.1 VDD

FSCK SCK frequency - - 10 MHz

tch SCK high time 50 - - ns

tcl SCK low time 50 - - ns

trise SCK rise time - 5 - ns

tfall SCK fall time - 5 - ns

tsetup MOSI setup time From MOSI change to SCK rising

edge.

30 - - ns

thold MOSI hold time From SCK rising edge to MOSI

change.

20 - - ns

tnsetup NSS setup time From NSS falling edge to SCK rising

edge.

30 - - ns

tnhold NSS hold time From SCK falling edge to NSS rising

edge, normal mode.

100 - - ns

tnhigh NSS high time between SPI

accesses

20 - - ns

T_DATA DATA hold and setup time 250 - - ns

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3. SX1276/77/78/79 Features

This section gives a high-level overview of the functionality of the SX1276/77/78/79 low-power, highly integrated

transceiver. The following figure shows a simplified block diagram of the SX1276/77/78/79.

Figure 4. SX1276/77/78/79 Block Schematic Diagram

SX1276/77/78/79 is a half-duplex, low-IF transceiver. Here the received RF signal is first amplified by the LNA. The LNA

inputs are single ended to minimize the external BoM and for ease of design. Following the LNA inputs, the conversion to

differential is made to improve the second order linearity and harmonic rejection. The signal is then down-converted to in-

phase and quadrature (I&Q) components at the intermediate frequency (IF) by the mixer stage. A pair of sigma delta ADCs

then perform data conversion, with all subsequent signal processing and demodulation performed in the digital domain.

The digital state machine also controls the automatic frequency correction (AFC), received signal strength indicator (RSSI)

and automatic gain control (AGC). It also features the higher-level packet and protocol level functionality of the top level

sequencer (TLS), only available with traditional FSK and OOK modulation schemes.

The frequency synthesizers generate the local oscillator (LO) frequency for both receiver and transmitter, one covering the

lower UHF bands (up to 525 MHz), and the other one covering the upper UHF bands (from 779 MHz). The PLLs are

optimized for user-transparent low lock time and fast auto-calibrating operation. In transmission, frequency modulation is

performed digitally within the PLL bandwidth. The PLL also features optional pre-filtering of the bit stream to improve

spectral purity.

SX1276/77/78/79 feature three distinct RF power amplifiers. Two of those, connected to RFO_LF and RFO_HF, can deliver

up to +14 dBm, are unregulated for high power efficiency and can be connected directly to their respective RF receiver

inputs via a pair of passive components to form a single antenna port high efficiency transceiver. The third PA, connected to

the PA_BOOST pin and can deliver up to +20 dBm via a dedicated matching network. Unlike the high efficiency PAs, this

high-stability PA covers all frequency bands that the frequency synthesizer addresses.

SX1276/77/78/79 also include two timing references, an RC oscillator and a 32 MHz crystal oscillator.

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All major parameters of the RF front end and digital state machine are fully configurable via an SPI interface which gives

access to SX1276/77/78/79’s configuration registers. This includes a mode auto sequencer that oversees the transition

and calibration of the SX1276/77/78/79 between intermediate modes of operation in the fastest time possible.

The SX1276/77/78/79 are equipped with both standard FSK and long range spread spectrum (LoRaTM) modems.

Depending upon the mode selected either conventional OOK or FSK modulation may be employed or the LoRaTM spread

spectrum modem.

3.1. LoRaTM Modem

The LoRaTM modem uses a proprietary spread spectrum modulation technique. This modulation, in contrast to legacy

modulation techniques, permits an increase in link budget and increased immunity to in-band interference. At the same

time the frequency tolerance requirement of the crystal reference oscillator is relaxed - allowing a performance increase for

a reduction in system cost. For a detailed description of the design trade-offs and operation of the SX1276/77/78/79 please

consult Section 4.1 of the datasheet.

3.2. FSK/OOK Modem

In FSK/OOK mode the SX1276/77/78/79 supports standard modulation techniques including OOK, FSK, GFSK, MSK and

GMSK. The SX1276/77/78/79 is especially suited to narrow band communication thanks the low-IF architecture employed

and the built-in AFC functionality. For full information on the FSK/OOK modem please consult Section 4.2 of this document.

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4. SX1276/77/78/79 Digital Electronics

4.1. The LoRaTM Modem

The LoRaTM modem uses spread spectrum modulation and forward error correction techniques to increase the range and

robustness of radio communication links compared to traditional FSK or OOK based modulation. Examples of the

performance improvement possible, for several possible settings, are summarised in the table below. Here the spreading

factor and error correction rate are design variables that allow the designer to optimise the trade-off between occupied

bandwidth, data rate, link budget improvement and immunity to interference.

Table 12 Example LoRaTM Modem Performances, 868MHz Band

Notes - for all bandwidths lower than 62.5 kHz, it is advised to use a TCXO as a frequency reference. This is required to

meet the frequency error tolerance specifications given in the Electrical Specification

- Higher spreading factors and longer transmission times impose more stringent constraints on the short term

frequency stability of the reference. Please get in touch with a Semtech representative to implement extremely low

sensitivity products.

For European operation the range of crystal tolerances acceptable for each sub-band (of the ERC 70-03) is given in the

specifications table. For US based operation a frequency hopping mode is available that automates both the LoRaTM

spread spectrum and frequency hopping spread spectrum processes.

Another important facet of the LoRaTM modem is its increased immunity to interference. The LoRaTM modem is capable of

co-channel GMSK rejection of up to 20 dB. This immunity to interference permits the simple coexistence of LoRaTM

modulated systems either in bands of heavy spectral usage or in hybrid communication networks that use LoRaTM to

extend range when legacy modulation schemes fail.

Bandwidth

(kHz) Spreading Factor Coding rate Nominal Rb

(bps)

Sensitivity

indication

(dBm)

Frequency

Reference

10.4 64/5 782 -131

TCXO

12 4/5 24 -147

20.8 64/5 1562 -128

12 4/5 49 -144

62.5 64/5 4688 -121

XTAL

12 4/5 146 -139

125 64/5 9380 -118

12 4/5 293 -136

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4.1.1. Link Design Using the LoRaTM Modem

4.1.1.1. Overview

The LoRaTM modem is setup as shown in the following figure. This configuration permits the simple replacement of the

FSK modem with the LoRaTM modem via the configuration register setting RegOpMode. This change can be performed on

the fly (in Sleep operating mode) thus permitting the use of both standard FSK or OOK in conjunction with the long range

capability. The LoRaTM modulation and demodulation process is proprietary, it uses a form of spread spectrum modulation

combined with cyclic error correction coding. The combined influence of these two factors is an increase in link budget and

enhanced immunity to interference.

Figure 5. LoRaTM Modem Connectivity

A simplified outline of the transmit and receive processes is also shown above. Here we see that the LoRaTM modem has

an independent dual port data buffer FIFO that is accessed through an SPI interface common to all modes. Upon selection

of LoRaTM mode, the configuration register mapping of the SX1276/77/78/79 changes. For full details of this change

please consult the register description of Section 6.

So that it is possible to optimise the LoRaTM modulation for a given application, access is given to the designer to three

critical design parameters. Each one permitting a trade off between link budget, immunity to interference, spectral

occupancy and nominal data rate. These parameters are spreading factor, modulation bandwidth and error coding rate.

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4.1.1.2. Spreading Factor

The spread spectrum LoRaTM 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 represents the number of symbols sent per bit of information.

The range of values accessible with the LoRaTM modem are shown in the following table.

Table 13 Range of Spreading Factors

Note that the spreading factor, SpreadingFactor, 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, so link budget and

range, of the LoRa receiver.

Spreading Factor 6

SF = 6 Is a special use case for the highest data rate transmission possible with the LoRa modem. To this end several

settings must be activated in the SX1276/77/78/79 registers when it is in use. These settings are only valid for SF6 and

should be set back to their default values for other spreading factors:

Set SpreadingFactor = 6 in RegModemConfig2

The header must be set to Implicit mode.

Set the bit field DetectionOptimize of register RegLoRaDetectOptimize to value "0b101".

Write 0x0C in the register RegDetectionThreshold.

4.1.1.3. Coding Rate

To further improve the robustness of the link the LoRaTM modem employs cyclic error coding to perform forward error

detection and correction. Such error coding incurs a transmission overhead - the resultant additional data overhead per

transmission is shown in the table below.

Table 14 Cyclic Coding Overhead

SpreadingFactor

(RegModulationCfg)

Spreading Factor

(Chips / symbol)

LoRa Demodulator

SNR

664 -5 dB

7128 -7.5 dB

8256 -10 dB

9512 -12.5 dB

10 1024 -15 dB

11 2048 -17.5 dB

12 4096 -20 dB

CodingRate

(RegTxCfg1)

Cyclic Coding

Rate Overhead Ratio

14/5 1.25

24/6 1.5

34/7 1.75

44/8 2

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Forward error correction is particularly efficient in improving the reliability of the link in the presence of interference. So that

the coding rate (and so robustness to interference) can be changed in response to channel conditions - the coding rate can

optionally be included in the packet header for use by the receiver. Please consult Section 4.1.1.6 for more information on

the LoRaTM packet and header.

4.1.1.4. Signal 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. There are of course regulatory constraints in most countries on the

permissible occupied bandwidth. Contrary to the FSK modem which is described in terms of the single sideband

bandwidth, the LoRaTM modem bandwidth refers to the double sideband bandwidth (or total channel bandwidth). The

range of bandwidths relevant to most regulatory situations is given in the LoRaTM modem specifications table (see Section

2.5.5).

Table 15 LoRa Bandwidth Options

Note In the lower band (169 MHz), the 250 kHz and 500 kHz bandwidths are not supported.

4.1.1.5. LoRaTM Transmission Parameter Relationship

With a knowledge of the key parameters that can be controlled by the user we define the LoRaTM symbol rate as:

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.

Bandwidth

(kHz) Spreading Factor Coding rate Nominal Rb

(bps)

7.8 12 4/5 18

10.4 12 4/5 24

15.6 12 4/5 37

20.8 12 4/5 49

31.2 12 4/5 73

41.7 12 4/5 98

62.5 12 4/5 146

125 12 4/5 293

250 12 4/5 586

500 12 4/5 1172

Rs BW

2SF

---------

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4.1.1.6. LoRaTM Packet Structure

The LoRaTM modem employs two types of packet format, 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.

The LoRaTM packet comprises three elements:

A preamble.

An optional header.

The data payload.

Figure 6. LoRaTM Packet Structure

Preamble

The preamble is used to synchronize receiver with the incoming data flow. 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 to receiver duty cycle in receive intensive applications. However, the minimum length suffices for all

communication. The transmitted preamble length may be changed by setting the register PreambleLength from 6 to 65535,

yielding total preamble lengths of 6+4 to 65535+4 symbols, once the fixed overhead of the preamble data is considered.

This permits the transmission of a near arbitrarily long preamble sequence.

The receiver undertakes a preamble detection process that periodically restarts. For this reason the preamble length

should be configured 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.

Header

Depending upon the chosen mode of operation two types of header are available. The header type is selected by the

ImplicitHeaderModeOn bit found within the RegModemConfig1 register.

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 code rate

The presence of an optional 16-bits CRC for the payload.

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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.

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

on both sides of the radio link.

Note With SF = 6 selected, implicit header mode is the only mode of operation possible.

Explicit Header Mode:

In Explicit Header Mode, the presence of the CRC at the end of the payload in selected only on the transmitter side through

the bit RxPayloadCrcOn in the register RegModemConfig1.

On the receiver side, the bit RxPayloadCrcOn in the register RegModemConfig1 is not used and once the payload has

been received, the user should check the bit CrcOnPayload in the register RegHopChannel. If the bit CrcOnPayload is at

‘1’, the user should then check the Irq Flag PayloadCrcError to make sure the CRC is valid.

If the bit CrcOnPayload is at ‘0’, it means there was no CRC on the payload and thus the IRQ Flag PayloadCrcError will not

be trigged even if the payload has errors.

Implicit Header Mode;

In Implicit Header Mode, it is necessary to set the bit RxPayloadCrcOn in the register RegModemConfig1 on both sides

(TX and RX)

Explicit Header Transmitter Receiver CRC Status

Value of the bit

RxPayloadCrcOn

00 CRC is not checked

01 CRC is not checked

10 CRC is checked

11 CRC is checked

Implicit Header Transmitter Receiver CRC Status

Value of the bit

RxPayloadCrcOn

00 CRC is not checked

0 1 CRC is always

wrong

10 CRC is not checked

11 CRC is checked

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Low Data Rate Optimization

Given the potentially long duration of the packet at high spreading factors the option is given to improve the robustness of

the transmission to variations in frequency over the duration of the packet transmission and reception. The bit

LowDataRateOptimize increases the robustness of the LoRa link at these low effective data rates. Its use is mandated

when the symbol duration exceeds 16ms. Note that both the transmitter and the receiver must have the same setting for

LowDataRateOptimize.

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 in the register settings in implicit mode. An optional CRC may be appended. For more

information on the payload and how it is loaded from the data buffer FIFO please see Section 4.1.2.3.

4.1.1.7. Time on air

For a given combination of spreading factor (SF), coding rate (CR) and signal bandwidth (BW) the total on-the-air

transmission time of a LoRaTM packet can be calculated as follows. From the definition of the symbol rate it is convenient

to define the symbol rate:

The LoRa packet duration is the sum of the duration of the preamble and the transmitted packet. The preamble length is calculated as

follows:

where npreamble is the programmed preamble length, taken from the registers RegPreambleMsb and RegPreambleLsb.The

payload duration depends upon the header mode that is enabled. The following formula gives the number of payload

symbols.

With the following dependencies:

PL is the number of Payload bytes (1 to 255)

SF is the spreading factor (6 to 12)

IH=0 when the header is enabled, IH=1 when no header is present

DE=1 when LowDataRateOptimize=1, DE=0 otherwise

CR is the coding rate (1 corresponding to 4/5, 4 to 4/8)

The Payload duration is then the symbol period multiplied by the number of Payload symbols

The time on air, or packet duration, in simply then the sum of the preamble and payload duration.

Ts 1

------

Tpreamble npreamble 4.25+()Tsym

npayload 8max ceil 8PL 4SF–2816CRC 20IH–++()

4SF 2DE–()

---------------------------------------------------------------------------------------- CR 4+()0,





Tpayload npayload Ts

×=

Tpacket Tpreamble Tpayload

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4.1.1.8. Frequency Hopping with LoRaTM

Frequency hopping spread spectrum (FHSS) is typically employed when the duration of a single packet could exceed

regulatory requirements relating to the maximum permissible channel dwell time. This is most notably the case in US

operation where the 902 to 928 MHz ISM band which makes provision for frequency hopping operation. To ease the

implementation of FHSS systems the frequency hopping mode of the LoRaTM modem can be enabled by setting

FreqHoppingPeriod to a non-zero value in register RegHopPeriod.

Principle of Operation

The principle behind the FHSS scheme is that a portion of each LoRaTM packet is transmitted on each hopping channel

from a look up table of frequencies managed by the host microcontroller. After a predetermined hopping period the

transmitter and receiver change to the next channel in a predefined list of hopping frequencies to continue transmission

and reception of the next portion of the packet. The time which the transmission will dwell in any given channel is

determined by FreqHoppingPeriod which is an integer multiple of symbol periods:

The frequency hopping transmission and reception process starts at channel 0. The preamble and header are transmitted

first on channel 0. At the beginning of each transmission the channel counter FhssPresentChannel (located in the register

RegHopChannel) is incremented and the interrupt signal FhssChangeChannel is generated. The new frequency must then

be programmed within the hopping period to ensure it is taken into account for the next hop, the interrupt

ChangeChannelFhss is then to be cleared by writing a logical ‘1’.

FHSS Reception always starts on channel 0. The receiver waits for a valid preamble detection before starting the

frequency hopping process as described above. Note that in the eventuality of header CRC corruption, the receiver will

automatically request channel 0 and recommence the valid preamble detection process.

Timing of Channel Updates

The interrupt requesting the channel change, FhssChangeChannel, is generated upon transition to the new frequency. The

frequency hopping process is illustrated in the diagram below:

HoppingPeriod Ts FreqHoppingPeriod×=

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Figure 7. Interrupts Generated in the Case of Successful Frequency Hopping Communication.

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4.1.2. LoRaTM Digital Interface

The LoRaTM modem comprises three types of digital interface, static configuration registers, status registers and a FIFO

data buffer. All are accessed through the SX1276/77/78/79’s SPI interface - full details of each type of register are given

below. Full listings of the register addresses used for SPI access are given in Section 6.4.

4.1.2.1. LoRaTM Configuration Registers

Configuration registers are accessed through the SPI interface. Registers are readable in all device mode including Sleep.

However, they should be written only in Sleep and Standby modes. Please note that the automatic top level

sequencer (TLS modes) are not available in LoRaTM mode and the configuration register mapping changes as

shown in Table 41. The content of the LoRaTM configuration registers is retained in FSK/OOK mode. For the functionality

of mode registers common to both FSK/OOK and LoRaTM mode, please consult the Analog and RF Front End section of

this document (Section 5).

4.1.2.2. Status Registers

Status registers provide status information during receiver operation.

4.1.2.3. LoRaTM Mode FIFO Data Buffer

Overview

The SX1276/77/78/79 is equipped with a 256 byte RAM data buffer which is uniquely accessible in LoRa mode. This RAM

area, herein referred to as the FIFO Data buffer, is fully customizable by the user and allows access to the received, or to

be transmitted, data. All access to the LoRaTM FIFO data buffer is done via the SPI interface. A diagram of the user defined

memory mapping of the FIFO data buffer is shown below. These FIFO data buffer can be read in all operating modes

except sleep and store data related to the last receive operation performed. It is automatically cleared of old content upon

each new transition to receive mode.

Figure 8. LoRaTM Data Buffer

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Principle of Operation

Thanks to its dual port configuration, it is possible to simultaneously store both transmit and receive information in the FIFO

data buffer. The register RegFifoTxBaseAddr specifies the point in memory where the transmit information is stored.

Similarly, for receiver operation, the register RegFifoRxBaseAddr indicates the point in the data buffer where information

will be written to in event of a receive operation.

By default, the device is configured at power up so that half of the available memory is dedicated to Rx

(RegFifoRxBaseAddr initialized at address 0x00) and the other half is dedicated for Tx (RegFifoTxBaseAddr initialized at

address 0x80).

However, due to the contiguous nature of the FIFO 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 FIFO. To exploit the

maximum FIFO data buffer size in transmit or receive mode, the whole FIFO data buffer can be used in each mode by

setting the base addresses RegFifoTxBaseAddr and RegFifoRxBaseAddr at the bottom of the memory (0x00).

The FIFO data buffer is cleared when the device is put in SLEEP mode, consequently no access to the FIFO data buffer is

possible in sleep mode. However, the data in the FIFO data buffer are retained when switching across the other LoRaTM

modes of operation, so that a received packet can be retransmitted with minimum data handling on the controller side. The

FIFO data buffer is not self-clearing (unless if the device is put in sleep mode) and the data will only be “erased” when a

new set of data is written into the occupied memory location.

The FIFO data buffer location to be read from, or written to, via the SPI interface is defined by the address pointer

RegFifoAddrPtr. Before any read or write operation it is hence necessary to initialize this pointer to the corresponding base

value. Upon reading or writing to the FIFO data buffer (RegFifo) the address pointer will then increment automatically.

The register RegRxNbBytes defines the size of the memory location to be written in the event of a successful receive

operation. The register RegPayloadLength indicates the size of the memory location to be transmitted. In implicit header

mode, the register RegRxNbBytes is not used as the number of payload bytes is known. Otherwise, in explicit header

mode, the initial size of the receive buffer is set to the packet length in the received header. The register

RegFifoRxCurrentAddr indicates the location of the last packet received in the FIFO so that the last packet received can be

easily read by pointing the register RegFifoAddrPtr to this register.

It is important to notice that all the received data will be written to the FIFO data buffer even if the CRC is invalid, permitting

user defined post processing of corrupted data. It is also important to note that when receiving, if the packet size exceeds

the buffer memory allocated for the Rx, it will overwrite the transmit portion of the data buffer.

4.1.2.4. Interrupts in LoRa Mode

Two registers are used to control the IRQ in LoRa mode, the register RegIrqFlagsMask which is used to mask the

interrupts and the register RegIrqFlags which indicates which IRQ has been trigged.

In the register RegIrqFlagsMask, setting a bit to ‘1’ will mask the interrupt, meaning this interrupt is disactivated. By default

all the interrupt are available.

In the register RegIrqFlags, a ‘1’ indicates a given IRQ has been trigged and then the IRQ must be clear by writing a ‘1’.

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4.1.3. Operation of the LoRaTM Modem

4.1.3.1. Operating Mode Control

The operating modes of the LoRaTM modem are accessed by enabling LoRaTM mode (setting the LongRangeMode bit of

RegOpMode). Depending upon the operating mode selected the range of functionality and register access is given by the

following table:

Table 16 LoRaTM Operating Mode Functionality

It is possible to access any mode from any other mode by changing the value in the RegOpMode register.

Operating Mode Description

SLEEP

Low-power mode. In this mode only SPI and configuration registers are accessible. Lora FIFO is not

accessible.

Note that this is the only mode permissible to switch between FSK/OOK mode and LoRa mode.

STANDBY both Crystal oscillator and Lora baseband blocks are turned on.RF part and PLLs are disabled

FSTX This is a frequency synthesis mode for transmission. The PLL selected for transmission is locked and active

at the transmit frequency. The RF part is off.

FSRX This is a frequency synthesis mode for reception. The PLL selected for reception is locked and active at the

receive frequency. The RF part is off.

TX When activated the SX1276/77/78/79 powers all remaining blocks required for transmit, ramps the PA,

transmits the packet and returns to Standby mode.

RXCONTINUOUS When activated the SX1276/77/78/79 powers all remaining blocks required for reception, processing all

received data until a new user request is made to change operating mode.

RXSINGLE When activated the SX1276/77/78/79 powers all remaining blocks required for reception, remains in this

state until a valid packet has been received and then returns to Standby mode.

CAD When in CAD mode, the device will check a given channel to detect LoRa preamble signal

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4.1.4. Frequency Settings

Recalling that the frequency step is given by:

In order to set LO frequency values following registers are available.

Frf is a 24-bit register which defines carrier frequency. The carrier frequency relates to the register contents by following

formula:

4.1.5. Frequency Error Indication

The SX1276/77/78/79 derives its RF centre frequency from a crystal reference oscillator which has a finite frequency

precision. Errors in reference frequency will manifest themselves as errors of the same proportion from the RF centre

frequency.

In LoRa receive mode the SX1276/77/78/79 is capable of measuring the frequency offset between the receiver centre

frequency and that of an incoming LoRa signal. The modem is intolerant of frequency offsets in the region of +/- 25% of the

bandwidth and will accurately report the error over this same range.

The error is read by reading the three RegFei registers. The contents of which are a signed 20 bit two's compliment word,

FreqError. The frequency error is determined from the register contents by:

Where Fxtal is the crystal frequency.

To correct the measured frequency error there are two steps to be taken. First the frequency error is subtracted from the

RF centre frequency. This calculation must be performed locally (or in a look-up-table), no provision is made in the circuit to

apply the correction automatically.

Secondly, assuming that the frequency error is due to reference oscillator drift, the data rate of the LoRa modem must also

be compensated accordingly. This is done by

PpmOffset = 0.95 * measured Offset [PPM]

Where PpmOffset is the value to be programmed into register 0x27 and the measured Offset is the PPM drift equivalent to

the frequency error reported by the LoRa frequency error indicator. The PpmOffset value is a signed two’s compliment

value.

FSTEP

FXOSC

219

----------------

FRF FSTEP Frf 23 0(,)×=

FError

FreqError 224

Fxtal

------------------------------------------BW kHz[]

500

------------------------

×=

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4.1.6. LoRaTM Modem State Machine Sequences

The sequence for transmission and reception of data to and from the LoRaTM modem, together with flow charts of typical

sequences of operation, are detailed below.

Data Transmission Sequence

In transmit mode power consumption is optimized by enabling RF, PLL and PA blocks only when packet data needs to be

transmitted. Figure 9 shows a typical LoRaTM transmit sequence.

Figure 9. LoRaTM Modulation Transmission Sequence.

Static configuration registers can only be accessed in Sleep mode, Standby mode or FSTX mode.

The LoRaTM FIFO can only be filled in Standby mode.

Data transmission is initiated by sending TX mode request.

Upon completion the TxDone interrupt is issued and the radio returns to Standby mode.

Following transmission the radio can be manually placed in Sleep mode or the FIFO refilled for a subsequent Tx

operation.

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LoRaTM Transmit Data FIFO Filling

In order to write packet data into FIFO user should:

1Set FifoPtrAddr to FifoTxPtrBase.

2Write PayloadLength bytes to the FIFO (RegFifo)

Data Reception Sequence

Figure 10 shows typical LoRaTM receive sequences for both single and continuous receiver modes of operation.

Figure 10. LoRaTM Receive Sequence.

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The LoRa receive modem can work in two distinct mode

1. Single receive mode

2. Continuous receive mode

Those two modes correspond to different use cases and it is important to understand the subtle differences between them.

Single Reception Operating Mode

In this mode, the modem searches for a preamble during a given period of time. If a preamble hasn’t been found at the end

of the time window, the chip generates the RxTimeout interrupt and goes back to Standby mode. The length of the

reception window (in symbols) is defined by the RegSymbTimeout register and should be in the range of 4 (minimum time

for the modem to acquire lock on a preamble) up to 1023 symbols.

At the end of the payload, the RxDone interrupt is generated together with the interrupt PayloadCrcError if the payload

CRC is not valid. However, even when the CRC is not valid, the data are written in the FIFO data buffer for post processing.

Following the RxDone interrupt the radio goes to Standby mode.

The modem will also automatically return in Standby mode when the interrupts RxDone is generated. Therefore, this mode

should only be used when the time window of arrival of the packet is known. In other cases, the RX continuous mode

should be used.

In Rx single mode, low-power is achieved by turning off PLL and RF blocks as soon as a packet has been received. The

flow is as follows:

1 Set FifoAddrPtr to FifoRxBaseAddr.

2 Static configuration register device can be written in either Sleep mode, Standby mode or FSRX mode.

3 A single packet receive operation is initiated by selecting the operating mode RXSINGLE.

4 The receiver will then await the reception of a valid preamble. Once received, the gain of the receive chain is set.

Following the ensuing reception of a valid header, indicated by the ValidHeader interrupt in explicit mode. The packet

reception process commences. Once the reception process is complete the RxDone interrupt is set. The radio then returns

automatically to Standby mode to reduce power consumption.

5 The receiver status register PayloadCrcError should be checked for packet payload integrity.

6 If a valid packet payload has been received then the FIFO should be read (See Payload Data Extraction below). Should

a subsequent single packet reception need to be triggered, then the RXSINGLE operating mode must be re-selected to

launch the receive process again - taking care to reset the SPI pointer (FifoAddrPtr) to the base location in memory

(FifoRxBaseAddr).

Continuous Reception Operating Mode

In continuous receive mode, the modem scans the channel continuously for a preamble. Each time a preamble is detected

the modem tracks it until the packet is received and then carries on waiting for the next preamble.

If the preamble length exceeds the anticipated value set by the registers RegPreambleMsb and RegPreambleLsb (measured in

symbol periods) the preamble will be dropped and the search for a preamble restarted. However, this scenario will not be

flagged by any interrupt. In continuous RX mode, opposite to the single RX mode, the RxTimeout interrupt will never occur

and the device will never go in Standby mode automatically.

It is also important to note that the demodulated bytes are written in the data buffer memory in the order received. Meaning,

the first byte of a new packet is written just after the last byte of the preceding packet. The RX modem address pointer is

never reset as long as this mode is enabled. It is therefore necessary for the companion microcontroller to handle the

address pointer to make sure the FIFO data buffer is never full.

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In continuous mode the received packet processing sequence is given below.

1 Whilst in Sleep or Standby mode select RXCONT mode.

2 Upon reception of a valid header CRC the RxDone interrupt is set. The radio remains in RXCONT mode waiting for the

next RX LoRaTM packet.

3 The PayloadCrcError flag should be checked for packet integrity.

4 If packet has been correctly received the FIFO data buffer can be read (see below).

5 The reception process (steps 2 - 4) can be repeated or receiver operating mode exited as desired.

In continuous mode status information are available only for the last packet received, i.e. the corresponding registers

should be read before the next RxDone arrives.

Rx Single and Rx Continuous Use Cases

The LoRa single reception mode is used mainly in battery operated systems or in systems where the companion

microcontroller has a limited availability of timers. In such systems, the use of the timeout present in Rx Single reception

mode allows the end user to limit the amount of time spent in reception (and thus limiting the power consumption) while not

using any of the companion MCU timers (the MCU can then be in sleep mode while the radio is in the reception mode). The

RxTimeout interrupt generated at the end of the reception period is then used to wake-up the companion MCU. One of the

advantages of the RxSingle mode is that the interrupt RxTimeout will not be triggered if the device is currently receiving

data, thus giving the priority to the reception of the data over the timeout. However, if during the reception, the device loses

track of the data due to external perturbation, the device will drop the reception, flag the interrupt RxTimeout and go in

StandBy mode to decrease the power consumption of the system.

On the other hand, The LoRa continuous reception mode is used in systems which do not have power restrictions or on

system where the use of a companion MCU timer is preferred over the radio embedded timeout system. In RxContinuous

mode, the radio will track any LoRa signal present in the air and carry on the reception of packets until the companion MCU

sets the radio into another mode of operation. Upon reception the interrupt RxDone will be trigged but the device will stay in

Rx Mode, ready for the reception of the next packet.

Payload Data Extraction from FIFO

In order to retrieve received data from FIFO the user must ensure that ValidHeader, PayloadCrcError, RxDone and

RxTimeout interrupts in the status register RegIrqFlags are not asserted to ensure that packet reception has terminated

successfully (i.e. no flags should be set).

In case of errors the steps below should be skipped and the packet discarded. In order to retrieve valid received data from

the FIFO the user must:

RegRxNbBytes Indicates the number of bytes that have been received thus far.

RegFifoAddrPtr is a dynamic pointer that indicates precisely where the Lora modem received data has been written up

to.

Set RegFifoAddrPtr to RegFifoRxCurrentAddr. This sets the FIFO pointer to the location of the last packet received in

the FIFO. The payload can then be extracted by reading the register RegFifo, RegRxNbBytes times.

Alternatively, it is possible to manually point to the location of the last packet received, from the start of the current

packet, by setting RegFifoAddrPtr to RegFifoRxByteAddr minus RegRxNbBytes. The payload bytes can then be read

from the FIFO by reading the RegFifo address RegRxNbBytes times.

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Packet Filtering based on Preamble Start

The LoRa modem does automatically filter received packets based upon any addressing. However the SX1276/77/78/79

permit software filtering of the received packets based on the contents of the first few bytes of payload. A brief example is

given below for a 4 byte address, however, the address length can be selected by the designer.

The objective of the packet filtering process is to determine the presence, or otherwise, of a valid packet designed for the

receiver. If the packet is not for the receiver then the radio returns to sleep mode in order to improve battery life.

The software packet filtering process follows the steps below:

Each time the RxDone interrupt is received, latch the RegFifoRxByteAddr[7:0] register content in a variable, this

variable will be called start_address. The RegFifoRxByteAddr[7:0] register of the SX1276/77/78/79 gives in real time

the address of the last byte written in the data buffer + 1 (or the address at which the next byte will be written) by the

receive LoRa modem. So by doing this, we make sure that the variable start_address always contains the start address

of the next packet.

Upon reception of the interrupt ValidHeader, start polling the RegFifoRxByteAddr[7:0] register until it begins to

increment. The speed at which this register will increment depends on the Spreading factor, the error correction code

and the modulation bandwidth. (Note that this interrupt is still generated in implicit mode).

As soon as RegFifoRxByteAddr[7:0] >= start address + 4, the first 4 bytes (address) are stored in the FIFO data buffer.

These can be read and tested to see if the packet is destined for the radio and either remaining in Rx mode to receive

the packet or returning to sleep mode if not.

Receiver Timeout Operation

In LoRaTM Rx Single mode, a receiver timeout functionality is available that permits the receiver to listen for a

predetermined period of time before generating an interrupt signal to indicate that no valid packets have been received.

The timer is absolute and commences as soon as the radio is placed in single receive mode. The interrupt itself, RxTimeout,

can be found in the interrupt register RegIrqFlags. In Rx Single mode, the device will return to Standby mode as soon as

the interrupt occurs. The user must then clear the interrupt or go into Sleep mode before returning into Rx Single mode.

The programmed timeout value is expressed as a multiple of the symbol period and is given by:

TimeOut LoraRxTimeout Ts⋅=

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Channel Activity Detection

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 LoRaTM signals. Figure 11

shows the channel activity detection (CAD) process:

Figure 11. LoRaTM CAD Flow

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Principle of Operation

The channel activity detection mode is designed to detect a LoRa preamble on the radio channel with the best possible

power efficiency. Once in CAD mode, the SX1276/77/78/79 will perform a very quick scan of the band to detect a LoRa

packet preamble.

During a CAD the following operations take place:

The PLL locks

The radio receiver captures LoRa preamble symbol of data from the channel. The radio current consumption during that

phase corresponds to the specified Rx mode current

The radio receiver and the PLL turn off, and the modem digital processing starts.

The modem searches for a correlation between the radio captured samples and the ideal preamble waveform. This

correlation process takes a little bit less than a symbol period to perform. The radio current consumption during that

phase is greatly reduced.

Once the calculation is finished the modem generates the CadDone interrupt. If the correlation was successful,

CadDetected is generated simultaneously.

The chip goes back to Standby mode.

If a preamble was detected, clear the interrupt, then initiate the reception by putting the radio in RX single mode or RX

continuous mode.

The time taken for the channel activity detection is dependent upon the LoRa modulation settings used. For a given

configuration the typical CAD detection time is shown in the graph below, expressed as a multiple of the LoRa symbol

period. Of this period the radio is in receiver mode for (2SF + 32) / BW seconds. For the remainder of the CAD cycle the

radio is in a reduced consumption state.

Figure 12. CAD Time as a Function of Spreading Factor

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To illustrate this process and the respective consumption in each mode, the CAD process follows the sequence of events

outlined below:

Figure 13. Consumption Profile of the LoRa CAD Process

The receiver is then in full receiver mode for just over half of the activity detection, followed by a reduced consumption

processing phase where the consumption varies with the LoRa bandwidth as shown in the table below.

Table 17 LoRa CAD Consumption Figures

Note These numbers can be slightly lower when using Band 2 and 3, on the low frequency port.

4.1.6.1. Digital IO Pin Mapping

Six of SX1276/77/78/79’s general purpose IO pins are available used in LoRaTM mode. Their mapping is shown below and

depends upon the configuration of registers RegDioMapping1 and RegDioMapping2.

Bandwidth

(kHz)

Full Rx, IDDR_L

(mA)

Processing, IDDC_L

(mA)

7.8 to 41.7 11 5.2

62.5 11 5.6

125 11.5 6

250 12.4 6.8

500 13.8 8.3

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Table 18 DIO Mapping LoRaTM Mode

4.1.7. Modem Status Indicators

The state of the LoRa modem is accessible with the ModemStatus bits in RegModemStat. They can mostly used for debug

in Rx mode and the useful indicators are:

Bit 0: Signal Detected indicates that a valid LoRa preamble has been detected

Bit 1: Signal Synchronized indicates that the end of Preamble has been detected, the modem is in lock

Bit 3: Header Info Valid toggles high when a valid Header (with correct CRC) is detected

4.2. FSK/OOK Modem

4.2.1. Bit Rate Setting

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 continuous transmit mode (Section 4.2.12) the data stream to be transmitted can be input directly

to the modulator via pin 10 (DIO2/DATA) in an asynchronous manner, unless Gaussian filtering is used, in which case the

DCLK signal on pin 9 (DIO1/DCLK) is used to synchronize the data stream. See section 4.2.2.3 for details on the Gaussian

filter.

In Packet mode or in Continuous mode with Gaussian filtering enabled, the Bit Rate (BR) is controlled by bits Bitrate in

RegBitrateMsb and RegBitrateLsb

Note: BitrateFrac bits have no effect (i.e may be considered equal to 0) in OOK modulation mode.

The quantity BitrateFrac is hence designed to allow very high precision (max. 250 ppm programing resolution) for any

bitrate in the programmable range. Ta bl e 19 below shows a range of standard bitrates and the accuracy to within which

they may be reached.

Operating

Mode

DIOx

Mapping DIO5 DIO4 DIO3 DIO2 DIO1 DIO0

ALL

00 ModeReady CadDetected CadDone FhssChangeChannel RxTimeout RxDone

01 ClkOut PllLock ValidHeader FhssChangeChannel FhssChangeChannel TxDone

10 ClkOut PllLock PayloadCrcError FhssChangeChannel CadDetected CadDone

11 - - - - - -

BitRate FXOSC

BitRate 15 0(,)BitrateFrac

-------------------------------

-------------------------------------------------------------------------

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Table 19 Bit Rate Examples

4.2.2. FSK/OOK Transmission

4.2.2.1. FSK Modulation

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 given by:

To ensure correct modulation, the following limit applies:

Note No constraint applies to the modulation index of the transmitter, but the frequency deviation must be set between

600 Hz and 200 kHz.

Type BitRate

(15:8)

BitRate

(7:0)

(G)FSK

(G)MSK OOK Actual BR

(b/s)

Classical modem baud rates

(multiples of 1.2 kbps)

0x68 0x2B 1.2 kbps 1.2 kbps 1200.015

0x34 0x15 2.4 kbps 2.4 kbps 2400.060

0x1A 0x0B 4.8 kbps 4.8 kbps 4799.760

0x0D 0x05 9.6 kbps 9.6 kbps 9600.960

0x06 0x83 19.2 kbps 19.2 kbps 19196.16

0x03 0x41 38.4 kbps 38415.36

0x01 0xA1 76.8 kbps 76738.60

0x00 0xD0 153.6 kbps 153846.1

Classical modem baud rates

(multiples of 0.9 kbps)

0x02 0x2C 57.6 kbps 57553.95

0x01 0x16 115.2 kbps 115107.9

Round bit rates

(multiples of 12.5, 25 and

50 kbps)

0x0A 0x00 12.5 kbps 12.5 kbps 12500.00

0x05 0x00 25 kbps 25 kbps 25000.00

0x80 0x00 50 kbps 50000.00

0x01 0x40 100 kbps 100000.0

0x00 0xD5 150 kbps 150234.7

0x00 0xA0 200 kbps 200000.0

0x00 0x80 250 kbps 250000.0

0x00 0x6B 300 kbps 299065.4

Watch Xtal frequency 0x03 0xD1 32.768 kbps 32.768 kbps 32753.32

FDEV FSTEP Fdev 13 0(,)×=

FDEV

------- 250()kHz≤+

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4.2.2.2. OOK Modulation

OOK modulation is applied by switching on and off the power amplifier. Digital control and ramping are available to improve

the transient power response of the OOK transmitter.

4.2.2.3. Modulation Shaping

Modulation shaping can be applied in both OOK and FSK modulation modes, to improve the narrow band response of the

transmitter. Both shaping features are controlled with PaRamp bits in RegPaRamp.

In FSK mode, a Gaussian filter with BT = 0.5 or 1 is used to filter the modulation stream, at the input of the sigma-delta

modulator. If the Gaussian filter is enabled when the SX1276/77/78/79 is in Continuous mode, DCLK signal on pin 10

(DIO1/DCLK) will trigger an interrupt on the uC each time a new bit has to be transmitted. Please refer to section

4.2.12.2 for details.

When OOK modulation is used, the PA bias voltages are ramped up and down smoothly when the PA is turned on and

off, to reduce spectral splatter.

Note The transmitter must be restarted if the ModulationShaping setting is changed, in order to recalibrate the built-in

filter.

4.2.3. FSK/OOK Reception

4.2.3.1. FSK Demodulator

The FSK demodulator of the SX1276/77/78/79 is designed to demodulate FSK, GFSK, MSK and GMSK modulated

signals. It is most efficient when the modulation index of the signal is greater than 0.5 and below 10:

The output of the FSK demodulator can be fed to the Bit Synchronizer to provide the companion processor with a

synchronous data stream in Continuous mode.

4.2.3.2. OOK Demodulator

The OOK demodulator performs a comparison of the RSSI output and a threshold value. Three different threshold modes

are available, configured through bits OokThreshType in RegOokPeak.

The recommended mode of operation is the “Peak” threshold mode, illustrated in Figure 14:

0.5 β≤ 2FDEV

---------------------- 10≤=

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Figure 14. OOK Peak Demodulator Description

In peak threshold mode the comparison threshold level is the peak value of the RSSI, reduced by 6dB. In the absence of

an input signal, or during the reception of a logical ‘0’, the acquired peak value is decremented by one OokPeakThreshStep

every OokPeakThreshDec period.

When the RSSI output is null for a long time (for instance after a long string of “0” received, or if no transmitter is present),

the peak threshold level will continue falling until it reaches the “Floor Threshold”, programmed in OokFixedThresh.

The default settings of the OOK demodulator lead to the performance stated in the electrical specification. However, in

applications in which sudden signal drops are awaited during a reception, the three parameters should be optimized

accordingly.

Optimizing the Floor Threshold

OokFixedThresh determines the sensitivity of the OOK receiver, as it sets the comparison threshold for weak input signals

(i.e. those close to the noise floor). Significant sensitivity improvements can be generated if configured correctly.

Note that the noise floor of the receiver at the demodulator input depends on:

The noise figure of the receiver.

The gain of the receive chain from antenna to base band.

The matching - including SAW filter if any.

The bandwidth of the channel filters.

Zoom

Period as defined in

OokPeakThreshDec

Decay in dB as defined in

OokPeakThreshStep

Fixed 6dB difference

RSSI

[dBm]

Noise floor of

receiver

‘’Floor’’ threshold defined by

OokFixedThresh

Time

‘’Peak -6dB’’ Threshold

Zoom

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It is therefore important to note that the setting of OokFixedThresh will be application dependent. The following procedure

is recommended to optimize OokFixedThresh.

Figure 15. Floor Threshold Optimization

The new floor threshold value found during this test should be used for OOK reception with those receiver settings.

Optimizing OOK Demodulator for Fast Fading Signals

A sudden drop in signal strength can cause the bit error rate to increase. For applications where the expected signal drop

can be estimated, the following OOK demodulator parameters OokPeakThreshStep and OokPeakThreshDec can be

optimized as described below for a given number of threshold decrements per bit. Refer to RegOokPeak to access those

settings.

Set SX1276/7/8/9 in OOK Rx mode

Adjust Bit Rate, Channel filter BW

Default OokFixedThresh setting

No input signal

Continuous Mode

Optimization complete

Glitch activity

on DATA ?

Monitor DIO2/DATA pin

Increment

OokFixedThresh

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Alternative OOK Demodulator Threshold Modes

In addition to the Peak OOK threshold mode, the user can alternatively select two other types of threshold detectors:

Fixed Threshold: The value is selected through OokFixedThresh

Average Threshold: Data supplied by the RSSI block is averaged, and this operation mode should only be used with

DC-free encoded data.

4.2.3.3. Bit Synchronizer

The bit synchronizer provides a clean and synchronized digital output based upon timing recovery information gleaned

from the received data edge transitions. Its output is made available on pin DIO1/DCLK in Continuous mode and can be

disabled through register settings. However, for optimum receiver performance, especially in Continuous receive mode, its

use is strongly advised.

The Bit Synchronizer is automatically activated in Packet mode. Its bit rate is controlled by BitRateMsb and BitRateLsb in

RegBitrate.

Figure 16. Bit Synchronizer Description

To ensure correct operation of the Bit Synchronizer, the following conditions have to be satisfied:

A preamble (0x55 or 0xAA) of at least 12 bits is required for synchronization, the longer the synchronization phase is the

better the ensuing packet detection rate will be.

The subsequent payload bit stream must have at least one edge transition (either rising or falling) every 16 bits during

data transmission.

The absolute error between transmitted and received bit rate must not exceed 6.5%.

Raw demodulator

output

(FSK or OOK)

DCLK

DATA

BitSync Output

To pin DATA and

DCLK in continuous

mode

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4.2.3.4. Frequency Error Indicator

This frequency error indicator measures the frequency error between the programmed RF centre frequency and the carrier

frequency of the modulated input signal to the receiver. When the FEI is performed, the frequency error is measured and

the signed result is loaded in FeiValue in RegFei, in 2’s complement format. The time required for an FEI evaluation is 4 bit

periods.

To ensure correct operation of the FEI:

The measurement must be launched during the reception of preamble.

The sum of the frequency offset and the 20 dB signal bandwidth must be lower than the base band filter bandwidth. i.e.

The whole modulated spectrum must be received.

The 20 dB bandwidth of the signal can be evaluated as follows (double-side bandwidth):

The frequency error, in Hz, can be calculated with the following formula:

The FEI is enabled automatically upon the transition to receive mode and automatically updated every 4 bits.

4.2.3.5. AFC

The AFC is based on the FEI measurement, therefore the same input signal and receiver setting conditions apply. When

the AFC procedure is performed the AfcValue is directly subtracted from the register that defines the frequency of

operation of the chip, FRF

. The AFC is executed each time the receiver is enabled, if AfcAutoOn = 1.

When the AFC is enabled (AfcAutoOn = 1), the user has the option to:

Clear the former AFC correction value, if AfcAutoClearOn = 1. Allowing the next frequency correction to be performed

from the initial centre frequency.

Start the AFC evaluation from the previously corrected frequency. This may be useful in systems in which the centre

frequency experiences cumulative drift - such as the ageing of a crystal reference.

The SX1276/77/78/79 offers an alternate receiver bandwidth setting during the AFC phase allowing the accommodation of

larger frequency errors. The setting RegAfcBw sets the receive bandwidth during the AFC process. In a typical receiver

application the, once the AFC is performed, the radio will revert to the receiver communication or channel bandwidth

(RegRxBw) for the ensuing communication phase.

Note that the FEI measurement is valid only during the reception of preamble. The provision of the PreambleDetect flag

can hence be used to detect this condition and allow a reliable AFC or FEI operation to be triggered. This process can be

performed automatically by using the appropriate options in StartDemodOnPreamble found in the RegRxConfig register.

A detailed description of the receiver setup to enable the AFC is provided in section 4.2.6.

BW20dB 2FDEV

-------





×=

FEI FSTEP FeiValue×=

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4.2.3.6. Preamble Detector

The Preamble Detector indicates the reception of a carrier modulated with a 0101...sequence. It is insensitive to the

frequency offset, as long as the receiver bandwidth is large enough. The size of detection can be programmed from 1 to 3

bytes with PreambleDetectorSize in RegPreambleDetect as defined in the next table.

Table 20 Preamble Detector Settings

For normal operation, PreambleDetectTol should be set to be set to 10 (0x0A), with a qualifying preamble size of 2 bytes.

The PreambleDetect interrupt (either in RegIrqFlags1 or mapped to a specific DIO) then goes high every time a valid

preamble is detected, assuming PreambleDetectorOn=1.

The preamble detector can also be used as a gate to ensure that AFC and AGC are performed on valid preamble. See

section 4.2.6. for details.

4.2.3.7. Image Rejection Mixer

The SX1276/77/78/79 employs an image rejection mixer (IRM) which, uncalibrated, 35 dB image rejection. A low phase

noise PLL is used to perform calibration of the receiver chain. This increases the typical image rejection to 48 dB.

4.2.3.8. Image and RSSI Calibration

An automated process is implemented to calibrate the phase and gain imbalances of I and Q receive paths. This calibration

enhances image rejection and improves RSSI precision. It is launched under the following circumstances:

Automatically at Power On Reset or after a Manual Reset of the chip (refer to section 7.2), only for the Low Frequency

front-end, and is performed at 434MHz

Automatically when a pre-defined temperature change is observed, if the option is enabled. A selectable temperature

change, set with TempThreshold (5, 10, 15 or 20°C), is detected and reported in TempChange, if the temperature

monitoring is turned On with TempMonitorOff=0.This interrupt flag can be used by the application to launch a new

image calibration at a convenient time if AutoImageCalOn=0, or immediately when this temperature variation is

detected, if AutoImageCalOn=1

Upon user request, by setting bit ImageCalStart in RegImageCal, when the device is in Standby mode

Notes - The calibration procedure takes approximately 10ms. It is recommended to disable the fully automated

(temperature-dependent) calibration, to better control when it is triggered (and avoid unexpected packet losses)

- To perform the calibration, the radio must be temporarily returned to FSK/OOK mode

- The automatic IQ and RSSI calibration done at POR and Reset is only valid at 434 MHz (the value of RegFrf at

POR). To improve accuracy of RSSI and image rejection, this calibration should be replicated at the frequency (ies)

PreambleDetectorSize # of Bytes

00 1

01 2 (recommended)

10 3

11 reserved

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of interest, for instance a calibration should be launched with Frf set to 868.3 MHz if the high frequency port

supports communication in this frequency band. Conversely if the product is used at 169 MHz, the calibration

should be repeated with Frf=169MHz

- FormerTemp and TempChange in SX1276/77/79 are frequency-specific and the IC keeps a copy of these

variables when switching between the low frequency and the high frequency domains (along with the

corresponding calibration values, stored in test registers)

- FormerTemp and TempChange cannot be read in Sleep mode (although they are saved). They should be read in

Standby mode

4.2.3.9. Timeout Function

The SX1276/77/78/79 includes a Timeout function, which allows it to automatically shut-down the receiver after a receive

sequence and therefore save energy.

Timeout interrupt is generated TimeoutRxRssi x 16 x Tbit after switching to Rx mode if the Rssi flag does not raise

within this time frame (RssiValue > RssiThreshold)

Timeout interrupt is generated TimeoutRxPreamble x 16 x Tbit after switching to Rx mode if the PreambleDetect flag

does not raise within this time frame

Timeout interrupt is generated TimeoutSignalSync x 16 x Tbit after switching to Rx mode if the SyncAddress flag does

not raise within this time frame

This timeout interrupt can be used to warn the companion processor to shut down the receiver and return to a lower power

mode. To become active, these timeouts must also be enabled by setting the correct RxTrigger parameters in

RegRxConfig:

Table 21 RxTrigger Settings to Enable Timeout Interrupts

4.2.4. Operating Modes in FSK/OOK Mode

The SX1276/77/78/79 has several working modes, manually programmed in RegOpMode. Fully automated mode

selection, packet transmission and reception is also possible using the Top Level Sequencer described in Section 4.2.8.

Table 22 Basic Transceiver Modes

Receiver

Triggering Event

RxTrigger

(2:0)

Timeout on

Rssi

Timeout on

Preamble

Timeout on

SyncAddress

None 000 Off Off

Active

Rssi Interrupt 001 Active Off

PreambleDetect 110 Off Active

Rssi Interrupt & PreambleDetect 111 Active Active

Mode Selected mode Symbol Enabled blocks

000 Sleep mode Sleep None

001 Standby mode Stdby Top regulator and crystal oscillator

010 Frequency synthesiser to Tx

frequency FSTx Frequency synthesizer at Tx frequency (Frf)

011 Transmit mode Tx Frequency synthesizer and transmitter

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When switching from a mode to another the sub-blocks are woken up according to a pre-defined optimized sequence.

100 Frequency synthesiser to Rx

frequency FSRx Frequency synthesizer at frequency for reception (Frf-IF)

101 Receive mode Rx Frequency synthesizer and receiver

Mode Selected mode Symbol Enabled blocks

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4.2.5. Startup Times

The startup time of the transmitter or the receiver is Dependant upon which mode the transceiver was in at the beginning.

For a complete description, Figure 17 below shows a complete startup process, from the lower power mode “Sleep”.

Figure 17. Startup Process

TS_OSC is the startup time of the crystal oscillator which depends on the electrical characteristics of the crystal. TS_FS is

the startup time of the PLL including systematic calibration of the VCO.

Typical values of TS_OSC and TS_FS are given in Section 2.5.2.

4.2.5.1. Transmitter Startup Time

The transmitter startup time, TS_TR, is calculated as follows in FSK mode:

where PaRamp is the ramp-up time programmed in RegPaRamp and Tbit is the bit time.

In OOK mode, this equation can be simplified to the following:

4.2.5.2. Receiver Startup Time

The receiver startup time, TS_RE, only depends upon the receiver bandwidth effective at the time of startup. When AFC is

enabled (AfcAutoOn=1), AfcBw should be used instead of RxBw to extract the receiver startup time:

Sleep

mode

Transmit

Stdby

mode

FSTx

FSRx Receive

Timeline

0 TS_OSC TS_OSC

+TS_FS

TS_OSC

+TS_FS

+TS_TR

TS_OSC

+TS_FS

+TS_RE

Current

Drain

IDDSL IDDST

IDDFS

IDDR (Rx) or IDDT (Tx)

TbitPaRampsTRTS ×+×+=

25.15_

TbitsTRTS ×+=

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Table 23 Receiver Startup Time Summary

TS_RE or later after setting the device in Receive mode, any incoming packet will be detected and demodulated by the

transceiver.

4.2.5.3. Time to RSSI Evaluation

The first RSSI sample will be available TS_RSSI after the receiver is ready, in other words TS_RE + TS_RSSI after the

receiver was requested to turn on.

Figure 18. Time to RSSI Sample

TS_RSSI depends on the receiver bandwidth, as well as the RssiSmoothing option that was selected. The formula used to

calculate TS_RSSI is provided in section 5.5.4.

RxBw if AfcAutoOn=0

RxBwAfc if AfcAutoOn=1

TS_RE

(+/-5%)

2.6 kHz 2.33 ms

3.1 kHz 1.94 ms

3.9 kHz 1.56 ms

5.2 kHz 1.18 ms

6.3 kHz 984 us

7.8 kHz 791 us

10.4 kHz 601 us

12.5 kHz 504 us

15.6 kHz 407 us

20.8 kHz 313 us

25.0 kHz 264 us

31.3 kHz 215 us

41.7 kHz 169 us

50.0 kHz 144 us

62.5 kHz 119 us

83.3 kHz 97 us

100.0 kHz 84 us

125.0 kHz 71 us

166.7 kHz 85 us

200.0 kHz 74 us

250.0 kHz 63 us

FSRx Rx

Rssi IRQ

Rssi sample

ready

Timeline

0TS_RE TS_RE

+TS_RSSI

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4.2.5.4. Tx to Rx Turnaround Time

Figure 19. Tx to Rx Turnaround

Note The SPI instruction times are omitted, as they can generally be very small as compared to other timings (up to

10MHz SPI clock).

4.2.5.5. Rx to Tx

Figure 20. Rx to Tx Turnaround

Tx Mode 1. set new Frf (*)

2. set Rx mode

Timeline

0TS_HOP

+TS_RE

(*) Optional

Rx Mode

Rx Mode 1. set new Frf (*)

2. set Tx mode

Timeline

0TS_HOP

+TS_TR

(*) Optional

Tx Mode

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4.2.5.6. Receiver Hopping, Rx to Rx

Two methods are possible:

Figure 21. Receiver Hopping

The second method is quicker, and should be used if a very quick RF sniffing mechanism is to be implemented.

4.2.5.7. Tx to Tx

Figure 22. Transmitter Hopping

4.2.6. Receiver Startup Options

The SX1276/77/78/79 receiver can automatically control the gain of the receive chain (AGC) and adjust the receiver LO

frequency (AFC). Those processes are carried out on a packet-by-packet basis. They occur:

When the receiver is turned On.

When the Receiver is restarted upon user request, through the use of trigger bits RestartRxWithoutPllLock or

RestartRxWithPllLock, in RegRxConfig.

When the receiver is automatically restarted after the reception of a valid packet, or after a packet collision.

Rx Mode,

Channel A

1. set new Frf

2. set RestartRxWithPllLock

Timeline

0TS_HOP

+TS_RE

Rx Mode,

Channel B

First method

Rx Mode,

Channel A

1. set FastHopOn=1

2. set new Frf (*)

3. wait for TS_HOP

Timeline

0~TS_HOP

Rx Mode,

Channel B

Second method

(*) RegFrfLsb must be written to

trigger a frequency change

1. set new Frf (*)

2. set FSTx mode FSTx

Timeline

~PaRamp

+TS_HOP

~PaRamp

+TS_HOP

+TS_TR

Tx Mode,

Channel A

Tx Mode,

Channel B

Set Tx mode

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Automatic restart capabilities are detailed in Section 4.2.7.

The receiver startup options available in SX1276/77/78/79 are described in Tab l e 24.

Table 24 Receiver Startup Options

When AgcAutoOn=0, the LNA gain is manually selected by choosing LnaGain bits in RegLna.

4.2.7. Receiver Restart Methods

The options for restart of the receiver are covered below. This is typically of use to prepare for the reception of a new signal

whose strength or carrier frequency is different from the preceding packet to allow the AGC or AFC to be re-evaluated.

4.2.7.1. Restart Upon User Request

In Receive mode the user can request a receiver restart - this can be useful in conjunction with the use of a Timeout

interrupt following a period of inactivity in the channel of interest. Two options are available:

No change in the Local Oscillator upon restart: the AFC is disabled, and the Frf register has not been changed through

SPI before the restart instruction: set bit RestartRxWithoutPllLock in RegRxConfig to 1.

Local Oscillator change upon restart: if AFC is enabled (AfcAutoOn=1), and/or the Frf register had been changed during

the last Rx period: set bit RestartRxWithPllLock in RegRxConfig to 1.

Note ModeReady must be at logic level 1 for a new RestartRx command to be taken into account.

4.2.7.2. Automatic Restart after valid Packet Reception

The bits AutoRestartRxMode in RegSyncConfig control the automatic restart feature of the SX1276/77/78/79 receiver,

when a valid packet has been received:

If AutoRestartRxMode = 00, the function is off, and the user should manually restart the receiver upon valid packet

reception (see section 4.2.7.1).

If AutoRestartRxMode = 01, after the user has emptied the FIFO following a PayloadReady interrupt, the receiver will

automatically restart itself after a delay of InterPacketRxDelay, allowing for the distant transmitter to ramp down, hence

avoiding a false RSSI detection on the ‘tail’ of the previous packet.

If AutoRestartRxMode = 10 should be used if the next reception is expected on a new frequency, i.e. Frf is changed

after the reception of the previous packet. An additional delay is systematically added, in order for the PLL to lock at a

new frequency.

Triggering Event Realized Function AgcAutoOn AfcAutoOn RxTrigger

(2:0)

None None 0 0 000

Rssi Interrupt AGC 1 0 001

AGC & AFC 1 1 001

PreambleDetect AGC 1 0 110

AGC & AFC 1 1 110

Rssi Interrupt

PreambleDetect

AGC 1 0 111

AGC & AFC 1 1 111

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4.2.7.3. Automatic Restart when Packet Collision is Detected

In receive mode the SX1276/77/78/79 is able to detect packet collision and restart the receiver. Collisions are detected by

a sudden rise in received signal strength, detected by the RSSI. This functionality can be useful in network configurations

where many asynchronous slaves attempt periodic communication with a single a master node.

The collision detector is enabled by setting bit RestartRxOnCollision to 1.

The decision to restart the receiver is based on the detection of RSSI change. The sensitivity of the system can be adjusted

in 1 dB steps by using register RssiCollisionThreshold in RegRxConfig.

4.2.8. Top Level Sequencer

Depending on the application, it is desirable to be able to change the mode of the circuit according to a predefined

sequence without access to the serial interface. In order to define different sequences or scenarios, a user-programmable

state machine, called Top Level Sequencer (Sequencer in short), can automatically control the chip modes.

NOTE THAT THIS FUNCTIONALITY IS ONLY AVAILABLE IN FSK/OOK MODE.

The Sequencer is activated by setting the SequencerStart bit in RegSeqConfig1 to 1 in Sleep or Standby mode (called

initial mode).

It is also possible to force the Sequencer off by setting the Stop bit in RegSeqConfig1 to 1 at any time.

Note SequencerStart and Stop bit must never be set at the same time.

4.2.8.1. Sequencer States

As shown in the table below, with the aid of a pair of interrupt timers (T1 and T2), the sequencer can take control of the chip

operation in all modes.

Table 25 Sequencer States

Sequencer

State Description

SequencerOff State

The Sequencer is not activated. Sending a SequencerStart command will launch it.

When coming from LowPowerSelection state, the Sequencer will be Off, whilst the chip will

return to its initial mode (either Sleep or Standby mode).

Idle State The chip is in low-power mode, either Standby or Sleep, as defined by IdleMode in

RegSeqConfig1. The Sequencer waits only for the T1 interrupt.

Transmit State The transmitter in on.

Receive State The receiver in on.

PacketReceived The receiver is on and a packet has been received. It is stored in the FIFO.

LowPowerSelection Selects low power state (SequencerOff or Idle State)

RxTimeout Defines the action to be taken on a RxTimeout interrupt.

RxTimeout interrupt can be a TimeoutRxRssi, TimeoutRxPreamble or TimeoutSignalSync

interrupt.

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4.2.8.2. Sequencer Transitions

The transitions between sequencer states are listed in the forthcoming table.

Table 26 Sequencer Transition Options

Variable Transition

IdleMode

Selects the chip mode during Idle state:

0: Standby mode

1: Sleep mode

FromStart

Controls the Sequencer transition when the SequencerStart bit is set to 1 in Sleep or Standby mode:

00: to LowPowerSelection

01: to Receive state

10: to Transmit state

11: to Transmit state on a FifoThreshold interrupt

LowPowerSelection

Selects Sequencer LowPower state after a to LowPowerSelection transition

0: SequencerOff state with chip on Initial mode

1: Idle state with chip on Standby or Sleep mode depending on IdleMode

Note: Initial mode is the chip LowPower mode at Sequencer start.

FromIdle

Controls the Sequencer transition from the Idle state on a T1 interrupt:

0: to Transmit state

1: to Receive state

FromTransmit

Controls the Sequencer transition from the Transmit state:

0: to LowPowerSelection on a PacketSent interrupt

1: to Receive state on a PacketSent interrupt

FromReceive

Controls the Sequencer transition from the Receive state:

000 and 111: unused

001: to PacketReceived state on a PayloadReady interrupt

010: to LowPowerSelection on a PayloadReady interrupt

011: to PacketReceived state on a CrcOk interrupt. If CRC is wrong (corrupted packet, with CRC on but

CrcAutoClearOn is off), the PayloadReady interrupt will drive the sequencer to RxTimeout state.

100: to SequencerOff state on a Rssi interrupt

101: to SequencerOff state on a SyncAddress interrupt

110: to SequencerOff state on a PreambleDetect interrupt

Irrespective of this setting, transition to LowPowerSelection on a T2 interrupt

FromRxTimeout

Controls the state-machine transition from the Receive state on a RxTimeout interrupt (and on

PayloadReady if FromReceive = 011):

00: to Receive state via ReceiveRestart

01: to Transmit state

10: to LowPowerSelection

11: to SequencerOff state

Note: RxTimeout interrupt is a TimeoutRxRssi, TimeoutRxPreamble or TimeoutSignalSync interrupt.

FromPacketReceived

Controls the state-machine transition from the PacketReceived state:

000: to SequencerOff state

001: to Transmit on a FifoEmpty interrupt

010: to LowPowerSelection

011: to Receive via FS mode, if frequency was changed

100: to Receive state (no frequency change)

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4.2.8.3. Timers

Two timers (Timer1 and Timer2) are also available in order to define periodic sequences. These timers are used to

generate interrupts, which can trigger transitions of the Sequencer.

T1 interrupt is generated (Timer1Resolution * Timer1Coefficient) after T2 interrupt or SequencerStart. command.

T2 interrupt is generated (Timer2Resolution * Timer2Coefficient) after T1 interrupt.

The timers’ mechanism is summarized on the following diagram.

Figure 23. Timer1 and Timer2 Mechanism

Note The timer sequence is completed independently of the actual Sequencer state. Thus, both timers need to be on to

achieve periodic cycling.

Table 27 Sequencer Timer Settings

Variable Description

Timer1Resolution

Resolution of Timer1

00: disabled

01: 64 us

10: 4.1 ms

11: 262 ms

Timer2Resolution

Resolution of Timer2

00: disabled

01: 64 us

10: 4.1 ms

11: 262 ms

Timer1Coefficient Multiplying coefficient for Timer1

Timer2Coefficient Multiplying coefficient for Timer2

interrupt

Timer1

Timer2

Sequencer Start

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4.2.8.4. Sequencer State Machine

The following graphs summarize every possible transition between each Sequencer state. The Sequencer states are

highlighted in grey. The transitions are represented by arrows. The condition activating them is described over the

transition arrow. For better readability, the start transitions are separated from the rest of the graph.

Transitory states are highlighted in light grey, and exit states are represented in red. It is also possible to force the

Sequencer off by setting the Stop bit in RegSeqConfig1 to 1 at any time.

Figure 24. Sequencer State Machine

Sequencer: Start transitions

Sequencer: State machine

Transmit

LowPower

Selection Idle

Receive

Packet

Received

RxTimeout

If LowPowerSelection = 1

On T1 if FromIdle = 0

On PacketSent

if FromTransmit = 1

On PayloadReady if FromReceive = 001

On CrcOk if FromReceive = 011

On PayloadReady

if FromReceive = 010

If FromRxTimeout = 01

If FromRxTimeout = 10

If FromPacketReceived = 010

If FromPacketReceived = 100

Via FS mode if FromPacketReceived = 011

On PacketSent

if FromTransmit = 0

Via ReceiveRestart

if FromRxTimeout = 00

On RxTimeout

On T2

On T1 if FromIdle = 1

If LowPowerSelection = 0

( Mode Initial mode )

On Rssi if FromReceive = 100

On SyncAdress if FromReceive = 101

On Preamble if FromReceive = 110

If FromRxTimeout = 11

If FromPacketReceived = 000

Sequencer Off

Standby if IdleMode = 0

Sleep if IdleMode = 1

Transmit

LowPower

Selection Receive

Start

If FromStart = 00

If FromStart = 01 If FromStart = 10

Sequencer Off

Initial mode = Sleep or Standby

On SequencerStart bit rising edge

On FifoThreshold

if FromStart = 11

On PayloadReady if FromReceive = 011

(CRC failed and CrcAutoClearOn=0)

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4.2.9. Data Processing in FSK/OOK Mode

4.2.9.1. Block Diagram

Figure below illustrates the SX1276/77/78/79 data processing circuit. Its role is to interface the data to/from the modulator/

demodulator and the uC access points (SPI and DIO pins). It also controls all the configuration registers.

The circuit contains several control blocks which are described in the following paragraphs.

Figure 25. SX1276/77/78/79 Data Processing Conceptual View

The SX1276/77/78/79 implements several data operation modes, each with their own data path through the data

processing. Depending on the data operation mode selected, some control blocks are active whilst others remain disabled.

4.2.9.2. Data Operation Modes

The SX1276/77/78/79 has two different data operation modes selectable by the user:

Continuous mode: each bit transmitted or received is accessed in real time at the DIO2/DATA pin. This mode may be

used if adequate external signal processing is available.

Packet mode (recommended): user only provides/retrieves payload bytes to/from the FIFO. The packet is automatically

built with preamble, Sync word, and optional CRC and DC-free encoding schemes The reverse operation is performed

in reception. The uC processing overhead is hence significantly reduced compared to Continuous mode. Depending on

the optional features activated (CRC, etc) the maximum payload length is limited to 255, 2047 bytes or unlimited.

Each of these data operation modes is fully described in the following s.

CONTROL

SPI

PACKET

HANDLER

SYNC

RECOG.

DIO1

MISO

MOSI

SCK

NSS

Tx/Rx

Data

FIFO

(+SR)

Potential datapaths (data operation mode dependant)

DIO2

DIO0

DIO3

DIO4

DIO5

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4.2.10. FIFO

Overview and Shift Register (SR)

In packet mode of operation, both data to be transmitted and that has been received are stored in a configurable FIFO

(First In First Out) device. It is accessed via the SPI interface and provides several interrupts for transfer management.

The FIFO is 1 byte wide hence it only performs byte (parallel) operations, whereas the demodulator functions serially. A

shift register is therefore employed to interface the two devices. In transmit mode it takes bytes from the FIFO and outputs

them serially (MSB first) at the programmed bit rate to the modulator. Similarly, in Rx the shift register gets bit by bit data

from the demodulator and writes them byte by byte to the FIFO. This is illustrated in figure below.

Figure 26. FIFO and Shift Register (SR)

Note When switching to Sleep mode, the FIFO can only be used once the ModeReady flag is set (quasi immediate from

all modes except from Tx)

The FIFO size is fixed to 64 bytes.

Interrupt Sources and Flags

FifoEmpty: FifoEmpty interrupt source is high when byte 0, i.e. whole FIFO, is empty. Otherwise it is low. Note that when

retrieving data from the FIFO, FifoEmpty is updated on NSS falling edge, i.e. when FifoEmpty is updated to low state

the currently started read operation must be completed. In other words, FifoEmpty state must be checked after each

read operation for a decision on the next one (FifoEmpty = 0: more byte(s) to read; FifoEmpty = 1: no more byte to

read).

FifoFull: FifoFull interrupt source is high when the last FIFO byte, i.e. the whole FIFO, is full. Otherwise it is low.

FifoOverrunFlag: FifoOverrunFlag is set when a new byte is written by the user (in Tx or Standby modes) or the SR (in

Rx mode) while the FIFO is already full. Data is lost and the flag should be cleared by writing a 1, note that the FIFO will

also be cleared.

PacketSent: PacketSent interrupt source goes high when the SR's last bit has been sent.

FifoLevel: Threshold can be programmed by FifoThreshold in RegFifoThresh. Its behavior is illustrated in figure below.

Data Tx/Rx 8

SR (8bits)

byte0

byte1 FIFO

MSB LSB

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Figure 27. FifoLevel IRQ Source Behavior

Notes - FifoLevel interrupt is updated only after a read or write operation on the FIFO. Thus the interrupt cannot be

dynamically updated by only changing the FifoThreshold parameter

- FifoLevel interrupt is valid as long as FifoFull does not occur. An empty FIFO will restore its normal operation

FIFO Clearing

Table below summarizes the status of the FIFO when switching between different modes

Table 28 Status of FIFO when Switching Between Different Modes of the Chip

4.2.10.1. Sync Word Recognition

Overview

Sync word recognition (also called Pattern recognition) is activated by setting SyncOn in RegSyncConfig. The bit

synchronizer must also be activated in Continuous mode (automatically done in Packet mode).

The block behaves like a shift register; it continuously compares the incoming data with its internally programmed Sync

word and sets SyncAddressMatch when a match is detected. This is illustrated in Figure 28 below.

From To FIFO status Comments

Stdby Sleep Not cleared

Sleep Stdby Not cleared

Stdby/Sleep Tx Not cleared To allow the user to write the FIFO in Stdby/Sleep before Tx

Stdby/Sleep Rx Cleared

Rx Tx Cleared

Rx Stdby/Sleep Not cleared To allow the user to read FIFO in Stdby/Sleep mode after Rx

Tx Any Cleared

# of bytes in FIFO

FifoLevel

BB+1

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Figure 28. Sync Word Recognition

During the comparison of the demodulated data, the first bit received is compared with bit 7 (MSB) of RegSyncValue1 and

the last bit received is compared with bit 0 (LSB) of the last byte whose address is determined by the length of the Sync

word.

When the programmed Sync word is detected the user can assume that this incoming packet is for the node and can be

processed accordingly.

SyncAddressMatch is cleared when leaving Rx or FIFO is emptied.

Configuration

Size: Sync word size can be set from 1 to 8 bytes (i.e. 8 to 64 bits) via SyncSize in RegSyncConfig. In Packet mode this

field is also used for Sync word generation in Tx mode.

Value: The Sync word value is configured in SyncValue(63:0). In Packet mode this field is also used for Sync word

generation in Tx mode.

Note SyncValue choices containing 0x00 bytes are not allowed

Packet Handler

The packet handler is the block used in Packet mode. Its functionality is fully described in Section 4.2.13.

Control

The control block configures and controls the full chip's behavior according to the settings programmed in the configuration

registers.

Rx DATA

(NRZ)

DCLK

Bit N-x =

Sync_value[x]

Bit N-1 =

Sync_value[1]

Bit N =

Sync_value[0]

SyncAddressMatch

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4.2.11. Digital IO Pins Mapping

Six general purpose IO pins are available on the SX1276/77/78/79, and their configuration in Continuous or Packet mode

is controlled through RegDioMapping1 and RegDioMapping2.

Table 29 DIO Mapping, Continuous Mode

Table 30 DIO Mapping, Packet Mode

DIOx Mapping Sleep Standby FSRx/Tx Rx Tx

00 SyncAddress TxReady

01 Rssi / PreambleDetect -

10 RxReady TxReady

01 Rssi / PreambleDetect -

00 Timeout -

01 Rssi / PreambleDetect -

11 -

10 TimeOut -

11 -

00 ClkOut if RC

10 Rssi / PreambleDetect -

11 -

PllLock

ModeReady ModeReady

DIO0

DIO1

DIO3

DIO2

DIO5

DIO4

ModeReady ModeReady

Dclk

Data

ClkOut ClkOut

TempChange / LowBat TempChange / LowBat

TempChange / LowBat

PllLock

Data

DIOx Mapping Sleep Standby FSRx/Tx Rx Tx

00 PayloadReady PacketSent

01 CrcOk -

11 -

00 FifoLevel

01 FifoEmpty

10 FifoFull

00 FifoFull

01 RxReady -

10 TimeOut FifoFull

11 SyncAddress FifoFull

00 FifoEmpty

01 TxReady

10 FifoEmpty

11 FifoEmpt

00 -

10 TimeOut -

11 Rssi / PreambleDetect -

00 ClkOut if RC

11 -

FifoEmpty

ModeReady

FifoEmpty

DIO5 - PllLock

-Data

ClkOut ClkOut

ModeReady

DIO4 - PllLock

TempChange / LowBat TempChange / LowBat

DIO3 -

FifoEmpty

DIO2 -

FifoFull

FifoFull FifoFull

FifoEmpty

DIO1

FifoLevel

FifoEmpty FifoEmpty

FifoLevel

FifoFull FifoFull

DIO0

TempChange / LowBatTempChange / LowBat

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4.2.12. Continuous Mode

4.2.12.1. General Description

As illustrated in Figure 29, in Continuous mode the NRZ data to (from) the (de)modulator is directly accessed by the uC on

the bidirectional DIO2/DATA pin. The FIFO and packet handler are thus inactive.

Figure 29. Continuous Mode Conceptual View

4.2.12.2. Tx Processing

In Tx mode, a synchronous data clock for an external uC is provided on DIO1/DCLK pin. Clock timing with respect to the

data is illustrated in Figure 30. DATA is internally sampled on the rising edge of DCLK so the uC can change logic state

anytime outside the grayed out setup/hold zone.

Figure 30. Tx Processing in Continuous Mode

Note the use of DCLK is required when the modulation shaping is enabled.

CONTROL

SPI

SYNC

RECOG.

DIO1/DCLK

MISO

MOSI

SCK

NSS

Tx/Rx

Data

DIO2/DATA

DIO0

DIO3

DIO4

DIO5

DCLK

T_DATAT_DATA

DATA

(NRZ)

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4.2.12.3. Rx Processing

If the bit synchronizer is disabled, the raw demodulator output is made directly available on DATA pin and no DCLK signal

is provided.

Conversely, if the bit synchronizer is enabled, synchronous cleaned data and clock are made available respectively on

DIO2/DATA and DIO1/DCLK pins. DATA is sampled on the rising edge of DCLK and updated on the falling edge as

illustrated below.

Figure 31. Rx Processing in Continuous Mode

Note In Continuous mode it is always recommended to enable the bit synchronizer to clean the DATA signal even if the

DCLK signal is not used by the uC (bit synchronizer is automatically enabled in Packet mode).

4.2.13. Packet Mode

4.2.13.1. General Description

In Packet mode the NRZ data to (from) the (de)modulator is not directly accessed by the uC but stored in the FIFO and

accessed via the SPI interface.

In addition, the SX1276/77/78/79 packet handler performs several packet oriented tasks such as Preamble and Sync word

generation, CRC calculation/check, whitening/dewhitening of data, Manchester encoding/decoding, address filtering, etc.

This simplifies software and reduces uC overhead by performing these repetitive tasks within the RF chip itself.

Another important feature is ability to fill and empty the FIFO in Sleep/Stdby mode, ensuring optimum power consumption

and adding more flexibility for the software.

DATA (NRZ)

DCLK

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Figure 32. Packet Mode Conceptual View

Note The Bit Synchronizer is automatically enabled in Packet mode.

4.2.13.2. Packet Format

Fixed Length Packet Format

Fixed length packet format is selected when bit PacketFormat is set to 0 and PayloadLength is set to any value greater

than 0.

In applications where the packet length is fixed in advance, this mode of operation may be of interest to minimize RF

overhead (no length byte field is required). All nodes, whether Tx only, Rx only, or Tx/Rx should be programmed with the

same packet length value.

The length of the payload is limited to 2047 bytes.

The length programmed in PayloadLength relates only to the payload which includes the message and the optional

address byte. In this mode, the payload must contain at least one byte, i.e. address or message byte.

An illustration of a fixed length packet is shown below. It contains the following fields:

Preamble (1010...)

Sync word (Network ID)

Optional Address byte (Node ID)

Message data

Optional 2-bytes CRC checksum

CONTROL

SPI

PACKET

HANDLER

SYNC

RECOG.

DIO1

MISO

MOSI

SCK

NSS

Data

FIFO

(+SR)

DIO2

DIO0

DIO3

DIO4

DIO5

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Figure 33. Fixed Length Packet Format

Variable Length Packet Format

Variable length packet format is selected when bit PacketFormat is set to 1.

This mode is useful in applications where the length of the packet is not known in advance and can vary over time. It is then

necessary for the transmitter to send the length information together with each packet in order for the receiver to operate

properly.

In this mode the length of the payload, indicated by the length byte, is given by the first byte of the FIFO and is limited to

255 bytes. Note that the length byte itself is not included in its calculation. In this mode, the payload must contain at least 2

bytes, i.e. length + address or message byte.

An illustration of a variable length packet is shown below. It contains the following fields:

Preamble (1010...)

Sync word (Network ID)

Length byte

Optional Address byte (Node ID)

Message data

Message

Up to 2047 bytes

Address

byte

CRC

2-bytes

Sync Word

0 to 8 bytes

Payload

(

min 1 b

)

CRC checksum calculation

Fields added by the packet handler in Tx and processed and removed in Rx

Optional User provided fields which are part of the payload

Message part of the payload

Optional DC free data coding

Preamble

0 to 65536 bytes

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Optional 2-bytes CRC checksum

Figure 34. Variable Length Packet Format

Unlimited Length Packet Format

Unlimited length packet format is selected when bit PacketFormat is set to 0 and PayloadLength is set to 0. The user can

then transmit and receive packet of arbitrary length and PayloadLength register is not used in Tx/Rx modes for counting

the length of the bytes transmitted/received.

In Tx the data is transmitted depending on the TxStartCondition bit. On the Rx side the data processing features like

Address filtering, Manchester encoding and data whitening are not available if the sync pattern length is set to zero

(SyncOn = 0). The CRC detection in Rx is also not supported in this mode of the packet handler, however CRC generation

in Tx is operational. The interrupts like CrcOk & PayloadReady are not available either.

An unlimited length packet shown below is made up of the following fields:

Preamble (1010...).

Sync word (Network ID).

Optional Address byte (Node ID).

Message data

Optional 2-bytes CRC checksum (Tx only)

Figure 35. Unlimited Length Packet Format

4.2.13.3. Tx Processing

Message

Up to 255 bytes

Address

byte

Length

byte

CRC

2-bytes

Sync Word

0 to 8 bytes

Preamble

0 to 65536 bytes

Payload

(min 2 bytes)

CRC checksum calculation

Fields added by the packet handler in Tx and processed and removed in Rx

Optional User provided fields which are part of the payload

Message part of the payload

Optional DC free data coding

Message

unlimited length

Address

byte

Sync Word

0 to 8 bytes

Preamble

0 to 65535

bytes

Payload

Fields added by the packet handler in Tx and processed and removed in Rx

Optional User provided fields which are part of the payload

Message part of the payload

DC free Data encoding

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In Tx mode the packet handler dynamically builds the packet by performing the following operations on the payload

available in the FIFO:

Add a programmable number of preamble bytes

Add a programmable Sync word

Optionally calculating CRC over complete payload field (optional length byte + optional address byte + message) and

appending the 2 bytes checksum.

Optional DC-free encoding of the data (Manchester or whitening)

Only the payload (including optional address and length fields) is required to be provided by the user in the FIFO.

The transmission of packet data is initiated by the Packet Handler only if the chip is in Tx mode and the transmission

condition defined by TxStartCondition is fulfilled. If transmission condition is not fulfilled then the packet handler transmits a

preamble sequence until the condition is met. This happens only if the preamble length /= 0, otherwise it transmits a zero or

one until the condition is met to transmit the packet data.

The transmission condition itself is defined as:

if TxStartCondition = 1, the packet handler waits until the first byte is written into the FIFO, then it starts sending the

preamble followed by the sync word and user payload

If TxStartCondition = 0, the packet handler waits until the number of bytes written in the FIFO is equal to the number

defined in RegFifoThresh + 1

If the condition for transmission was already fulfilled i.e. the FIFO was filled in Sleep/Stdby then the transmission of

packet starts immediately on enabling Tx

4.2.13.4. Rx Processing

In Rx mode the packet handler extracts the user payload to the FIFO by performing the following operations:

Receiving the preamble and stripping it off

Detecting the Sync word and stripping it off

Optional DC-free decoding of data

Optionally checking the address byte

Optionally checking CRC and reflecting the result on CrcOk.

Only the payload (including optional address and length fields) is made available in the FIFO.

When the Rx mode is enabled the demodulator receives the preamble followed by the detection of sync word. If fixed

length packet format is enabled then the number of bytes received as the payload is given by the PayloadLength

parameter.

In variable length mode the first byte received after the sync word is interpreted as the length of the received packet. The

internal length counter is initialized to this received length. The PayloadLength register is set to a value which is greater

than the maximum expected length of the received packet. If the received length is greater than the maximum length stored

in PayloadLength register the packet is discarded otherwise the complete packet is received.

If the address check is enabled then the second byte received in case of variable length and first byte in case of fixed

length is the address byte. If the address matches to the one in the NodeAddress field, reception of the data continues

otherwise it's stopped. The CRC check is performed if CrcOn = 1 and the result is available in CrcOk indicating that the

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CRC was successful. An interrupt (PayloadReady) is also generated on DIO0 as soon as the payload is available in the

FIFO. The payload available in the FIFO can also be read in Sleep/Standby mode.

If the CRC fails the PayloadReady interrupt is not generated and the FIFO is cleared. This function can be overridden by

setting CrcAutoClearOff = 1, forcing the availability of PayloadReady interrupt and the payload in the FIFO even if the CRC

fails.

4.2.13.5. Handling Large Packets

When PayloadLength exceeds FIFO size (64 bytes) whether in fixed, variable or unlimited length packet format, in addition

to PacketSent in Tx and PayloadReady or CrcOk in Rx, the FIFO interrupts/flags can be used as described below:

For Tx:

FIFO can be prefilled in Sleep/Standby but must be refilled “on-the-fly” during Tx with the rest of the payload.

1) Pre-fill FIFO (in Sleep/Standby first or directly in Tx mode) until FifoThreshold or FifoFull is set

2) In Tx, wait for FifoThreshold or FifoEmpty to be set (i.e. FIFO is nearly empty)

3) Write bytes into the FIFO until FifoThreshold or FifoFull is set.

4) Continue to step 2 until the entire message has been written to the FIFO (PacketSent will fire when the last bit of the

packet has been sent).

For Rx:

FIFO must be unfilled “on-the-fly” during Rx to prevent FIFO overrun.

1) Start reading bytes from the FIFO when FifoEmpty is cleared or FifoThreshold becomes set.

2) Suspend reading from the FIFO if FifoEmpty fires before all bytes of the message have been read

3) Continue to step 1 until PayloadReady or CrcOk fires

4) Read all remaining bytes from the FIFO either in Rx or Sleep/Standby mode

4.2.13.6. Packet Filtering

The SX1276/77/78/79 packet handler offers several mechanisms for packet filtering, ensuring that only useful packets are

made available to the uC, reducing significantly system power consumption and software complexity.

Sync Word Based

Sync word filtering/recognition is used for identifying the start of the payload and also for network identification. As

previously described, the Sync word recognition block is configured (size, value) in RegSyncConfig and RegSyncValue(i)

registers. This information is used, both for appending Sync word in Tx, and filtering packets in Rx.

Every received packet which does not start with this locally configured Sync word is automatically discarded and no

interrupt is generated.

When the Sync word is detected, payload reception automatically starts and SyncAddressMatch is asserted.

Note Sync Word values containing 0x00 byte(s) are forbidden

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Address Based

Address filtering can be enabled via the AddressFiltering bits. It adds another level of filtering, above Sync word (i.e. Sync

must match first), typically useful in a multi-node networks where a network ID is shared between all nodes (Sync word)

and each node has its own ID (address).

Two address based filtering options are available:

AddressFiltering = 01: Received address field is compared with internal register NodeAddress. If they match then the

packet is accepted and processed, otherwise it is discarded.

AddressFiltering = 10: Received address field is compared with internal registers NodeAddress and BroadcastAddress.

If either is a match, the received packet is accepted and processed, otherwise it is discarded. This additional check with

a constant is useful for implementing broadcast in a multi-node networks

Please note that the received address byte, as part of the payload, is not stripped off the packet and is made available in

the FIFO. In addition, NodeAddress and AddressFiltering only apply to Rx. On Tx side, if address filtering is expected, the

address byte should simply be put into the FIFO like any other byte of the payload.

As address filtering requires a Sync word match, both features share the same interrupt flag SyncAddressMatch.

Length Based

In variable length Packet mode, PayloadLength must be programmed with the maximum payload length permitted. If

received length byte is smaller than this maximum then the packet is accepted and processed, otherwise it is discarded.

Please note that the received length byte, as part of the payload, is not stripped off the packet and is made available in the

FIFO.

To disable this function the user should set the value of the PayloadLength to 2047.

CRC Based

The CRC check is enabled by setting bit CrcOn in RegPacketConfig1. It is used for checking the integrity of the message.

On Tx side a two byte CRC checksum is calculated on the payload part of the packet and appended to the end of the

message

On Rx side the checksum is calculated on the received payload and compared with the two checksum bytes received.

The result of the comparison is stored in bit CrcOk.

By default, if the CRC check fails then the FIFO is automatically cleared and no interrupt is generated. This filtering function

can be disabled via CrcAutoClearOff bit and in this case, even if CRC fails, the FIFO is not cleared and only PayloadReady

interrupt goes high. Please note that in both cases, the two CRC checksum bytes are stripped off by the packet handler

and only the payload is made available in the FIFO. Two CRC implementations are selected with bit CrcWhiteningType.

Table 31 CRC Description

A C code implementation of each CRC type is proposed in Application Section 7.

Crc Type CrcWhiteningType Polynomial Seed Value Complemented

CCITT 0 (default) X16 + X12 + X5 + 1 0x1D0F Yes

IBM 1X16 + X15 + X2 + 1 0xFFFF No

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4.2.13.7. DC-Free Data Mechanisms

The payload to be transmitted may contain long sequences of 1's and 0's, which introduces a DC bias in the transmitted

signal. The radio signal thus produced has a non uniform power distribution over the occupied channel bandwidth. It also

introduces data dependencies in the normal operation of the demodulator. Thus it is useful if the transmitted data is random

and DC free.

For such purposes, two techniques are made available in the packet handler: Manchester encoding and data whitening.

Note Only one of the two methods can be enabled at a time.

Manchester Encoding

Manchester encoding/decoding is enabled if DcFree = 01 and can only be used in Packet mode.

The NRZ data is converted to Manchester code by coding '1' as “10” and '0' as “01”.

In this case, the maximum chip rate is the maximum bit rate given in the specifications and the actual bit rate is half the chip

rate.

Manchester encoding and decoding is only applied to the payload and CRC checksum while preamble and Sync word are

kept NRZ. However, the chip rate from preamble to CRC is the same and defined by BitRate in RegBitRate (Chip Rate =

Bit Rate NRZ = 2 x Bit Rate Manchester).

Manchester encoding/decoding is thus made transparent for the user, who still provides/retrieves NRZ data to/from the

FIFO.

Figure 36. Manchester Encoding/Decoding

Data Whitening

Another technique called whitening or scrambling is widely used for randomizing the user data before radio transmission.

The data is whitened using a random sequence on the Tx side and de-whitened on the Rx side using the same sequence.

Comparing to Manchester technique it has the advantage of keeping NRZ data rate i.e. actual bit rate is not halved.

The whitening/de-whitening process is enabled if DcFree = 10. A 9-bit LFSR is used to generate a random sequence. The

payload and 2-byte CRC checksum is then XORed with this random sequence as shown below. The data is de-whitened

on the receiver side by XORing with the same random sequence.

Payload whitening/de-whitening is thus made transparent for the user, who still provides/retrieves NRZ data to/from the

FIFO.

...Sync Payload...

RF chips @ BR ... 1 1 1 0 1 0 0 1 0 0 1 0 1 1 0 1 0 ...

User/NRZ bits

Manchester OFF ... 1 1 1 0 1 0 0 1 0 0 1 0 1 1 0 1 0 ...

User/NRZ bits

Manchester ON ... 1 1 1 0 1 0 0 1 0 0 1 1 ...

1/BR

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Figure 37. Data Whitening Polynomial

4.2.13.8. Beacon Tx Mode

In some short range wireless network topologies a repetitive message, also known as beacon, is transmitted periodically

by a transmitter. The Beacon Tx mode allows for the re-transmission of the same packet without having to fill the FIFO

multiple times with the same data.

When BeaconOn in RegPacketConfig2 is set to 1, the FIFO can be filled only once in Sleep or Stdby mode with the

required payload. After a first transmission, FifoEmpty will go high as usual, but the FIFO content will be restored when the

chip exits Transmit mode. FifoEmpty, FifoFull and FifoLevel flags are also restored.

This feature is only available in Fixed packet format, with the Payload Length smaller than the FIFO size. The control of the

chip modes (Tx-Sleep-Tx....) can either be undertaken by the microcontroller, or be automated in the Top Sequencer. See

example in Section 4.2.13.8.

The Beacon Tx mode is exited by setting BeaconOn to 0, and clearing the FIFO by setting FifoOverrun to 1.

4.2.14. io-homecontrol® Compatibility Mode

The SX1276/77/78/79 features a io-homecontrol® compatibility mode. Please contact your local Semtech representative

for details on its implementation.

X7 X6 X5 X4 X3 X2 X1 X0

LFSR Polynomial =X9 + X5 + 1

Transmit data Whitened data

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4.3. 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.

Three access modes to the registers are provided:

SINGLE access: 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.

BURST access: the address byte is followed by several data bytes. The address is automatically incremented internally

between each data byte. This mode is available for both read and write accesses. The NSS pin goes low at the

beginning of the frame and stay low between each byte. It goes high only after the last byte transfer.

FIFO access: if the address byte corresponds to the address of the FIFO, then succeeding data byte will address the

FIFO. The address is not automatically incremented but is memorized and does not need to be sent between each data

byte. The NSS pin goes low at the beginning of the frame and stay low between each byte. It goes high only after the

last byte transfer.

The figure below shows a typical SPI single access to a register.

Figure 38. SPI Timing Diagram (single access)

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 first byte is the address byte. It is comprises:

A wnr bit, which is 1 for write access and 0 for read access.

Then 7 bits of address, MSB first.

The second byte is a data byte, either sent on MOSI by the master in case of a write access or received by the master on

MISO in case of read access. The data byte is transmitted MSB first.

Proceeding bytes may be sent on MOSI (for write access) or received on MISO (for read access) without a rising NSS

edge and re-sending the address. In FIFO mode, if the address was the FIFO address then the bytes will be written / read

at the FIFO address. In Burst mode, if the address was not the FIFO address, then it is automatically incremented for each

new byte received.

The frame ends when NSS goes high. The next frame must start with an address byte. The SINGLE access mode is

therefore a special case of FIFO / BURST mode with only 1 data byte transferred.

During the write access, the byte transferred from the slave to the master on the MISO line is the value of the written

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5. SX1276/77/78/79 Analog & RF Frontend Electronics

5.1. Power Supply Strategy

The SX1276/77/78/79 employs an internal voltage regulation scheme which provides stable operating voltage, and hence

device characteristics, over the full industrial temperature and operating voltage range of operation. This includes up to

+17 dBm of RF output power which is maintained from 1.8 V to 3.7 V and +20 dBm from 2.4 V to 3.7 V.

The SX1276/77/78/79 can be powered from any low-noise voltage source via pins VBAT_ANA, VBAT_RF and VBAT_DIG.

Decoupling capacitors should be connected, as suggested in the reference design of the applications section of this

document, on VR_PA, VR_DIG and VR_ANA pins to ensure correct operation of the built-in voltage regulators.

5.2. Low Battery Detector

A low battery detector is also included allowing the generation of an interrupt signal in response to the supply voltage

dropping below a programmable threshold that is adjustable through the register RegLowBat. The interrupt signal can be

mapped to any of the DIO pins by programming RegDioMapping.

5.3. Frequency Synthesis

5.3.1. Crystal Oscillator

The crystal oscillator is the main timing reference of the SX1276/77/78/79. It is used as the reference for the PLL’s

frequency synthesis and as the clock signal for all digital processing.

The crystal oscillator startup time, TS_OSC, depends on the electrical characteristics of the crystal reference used, for

more information on the electrical specification of the crystal see section 7.1. The crystal connects to the Pierce oscillator

on pins XTA and XTB. The SX1276/77/78/79 optimizes the startup time and automatically triggers the PLL when the

oscillator signal is stable.

Optionally, an external clock can be used to replace the crystal oscillator. This typically takes the form of a tight tolerance

temperature compensated crystal oscillator (TCXO). When using an external clock source the bit TcxoInputOn of register

RegTcxo should be set to 1 and the external clock has to be provided on XTA (pin 5). XTB (pin 6) should be left open.

The peak-peak amplitude of the input signal must never exceed 1.8 V. Please consult your TCXO supplier for an

appropriate value of decoupling capacitor, CD.

Figure 39. TCXO Connection

XTA XTB

32 MHz

TCXO

Vcc

GND CD

Vcc

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5.3.2. CLKOUT Output

The reference frequency, or a fraction of it, can be provided on DIO5 (pin 13) by modifying bits ClkOut in RegDioMapping2.

Two typical applications of the CLKOUT output include:

To provide a clock output for a companion processor, thus saving the cost of an additional oscillator. CLKOUT can be

made available in any operation mode except Sleep mode and is automatically enabled at power on reset.

To provide an oscillator reference output. Measurement of the CLKOUT signal enables simple software trimming of the

initial crystal tolerance.

Note To minimize the current consumption of the SX1276/77/78/79, please ensure that the CLKOUT signal is disabled

when not required.

5.3.3. PLL

The local oscillator of the SX1276/77/78/79 is derived from two almost identical fractional-N PLLs that are referenced to the

crystal oscillator circuit. Both PLLs feature a programmable bandwidth setting where one of four discrete preset bandwidths

may be accessed.

The SX1276/77/78/79 PLL uses a 19-bit sigma-delta modulator whose frequency resolution, constant over the whole

frequency range, is given by:

The carrier frequency is programmed through RegFrf, split across addresses 0x06 to 0x08:

Note The Frf setting is split across 3 bytes. A change in the center frequency will only be taken into account when the

least significant byte FrfLsb in RegFrfLsb is written. This allows the potential for user generation of m-ary FSK at

very low bit rates. This is possible where frequency modulation is achieved by direct programming of the

programmed RF centre frequency. To enable this functionality set the FastHopOn bit of register RegPllHop.

Three frequency bands are supported, defined as follows:

Table 32 Frequency Bands

* For SX1279

5.3.4. RC Oscillator

All timing operations in the low-power Sleep state of the Top Level Sequencer rely on the accuracy of the internal low-

power RC oscillator. This oscillator is automatically calibrated at the device power-up not requiring any user input.

Name Frequency Limits Products

Band 1 (HF) 862 (*779)-1020 (*960) MHz SX1276/77/79

Band 2 (LF) 410-525 (*480) MHz SX1276/77/78/79

Band 3 (LF) 137-175 (*160)MHz SX1276/77/78/79

FSTEP

FXOSC

219

----------------

FRF FSTEP Frf 23 0(,)×=

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5.4. Transmitter Description

The transmitter of SX1276/77/78/79 comprises the frequency synthesizer, modulator (both LoRaTM and FSK/OOK) and

power amplifier blocks, together with the DC biasing and ramping functionality that is provided through the VR_PA block.

5.4.1. Architecture Description

The architecture of the RF front end is shown in the following diagram:

Figure 40. RF Front-end Architecture Shows the Internal PA Configuration.

5.4.2. RF Power Amplifiers

PA_HF and PA_LF are high efficiency amplifiers capable of yielding RF power programmable in 1 dB steps from -4 to

+14dBm directly into a 50 ohm load with low current consumption. PA_LF covers the lower bands (up to 525 MHz), whilst

PA_HF will cover the upper bands (from 779 MHz). The output power is sensitive to the power supply voltage, and typically

their performance is expressed at 3.3V.

PA_HP (High Power), connected to the PA_BOOST pin, covers all frequency bands that the chip addresses. It permits

continuous operation at up to +17 dBm and duty cycled operation at up to +20dBm. For full details of operation at +20dBm

please consult section 5.4.3

Table 33 Power Amplifier Mode Selection Truth Table

Notes - For +20 dBm restrictions on operation please consult the following .

- To ensure correct operation at the highest power levels ensure that the current limiter OcpTrim is adjusted to

permit delivery of the requisite supply current.

- If the PA_BOOST pin is not used it may be left floating.

PaSelect Mode Power Range Pout Formula

0PA_HF or PA_LF on RFO_HF or RFO_LF -4 to +15dBm Pout=Pmax-(15-OutputPower)

Pmax=10.8+0.6*MaxPower [dBm]

1PA_HP on PA_BOOST, any frequency +2 to +17dBm Pout=17-(15-OutputPower) [dBm]

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5.4.3. High Power +20 dBm Operation

The SX1276/77/78/79 have a high power +20 dBm capability on PA_BOOST pin, with the following settings:

Table 34 High Power Settings

Notes - High Power settings must be turned off when using PA_LF or PA_HF

- The Over Current Protection limit should be adapted to the actual power level, in RegOcp

Specific Absolute Maximum Ratings and Operating Range restrictions apply to the +20 dBm operation. They are listed in

Tab le 35 and Ta bl e 36.

Table 35 Operating Range, +20dBm Operation

Table 36 Operating Range, +20dBm Operation

The duty cycle of transmission at +20 dBm is limited to 1%, with a maximum VSWR of 3:1 at antenna port, over the

standard operating range [-40;+85°C]. For any other operating condition, contact your Semtech representative.

High Power

Default value

PA_HF/LF or

+17dBm

Description

RegPaDac 0x4d 0x87 0x84 Set Pmax to +20dBm for PA_HP

Symbol Description Min Max Unit

DC_20dBm Duty Cycle of transmission at +20 dBm output - 1 %

VSWR_20dBm Maximum VSWR at antenna port, +20 dBm output -3:1 -

Symbol Description Min Max Unit

VDDop_20dBm Supply voltage, +20 dBm output 2.4 3.7 V

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5.4.4. Over Current Protection

The power amplifiers of SX1276/77/78/79 are protected against current over supply in adverse RF load conditions by the

over current protection block. This has the added benefit of protecting battery chemistries with limited peak current

capability and minimising worst case PA consumption in battery life calculation. The current limiter value is controlled by

the OcpTrim bits in RegOcp, and is calculated according to the following formulae:

Table 37 Trimming of the OCP Current

Note Imax sets a limit on the current drain of the Power Amplifier only, hence the maximum current drain of the SX1276/

77/78/79 is equal to Imax + IDDFS.

5.5. Receiver Description

5.5.1. Overview

The SX1276/77/78/79 features a digital receiver with the analog to digital conversion process being performed directly

following the LNA-Mixers block. In addition to the LoRaTM modulation scheme the low-IF receiver is able to demodulate

ASK, OOK, (G)FSK and (G)MSK modulation. All filtering, demodulation, gain control, synchronization and packet handling

is performed digitally allowing a high degree of programmable flexibility. The receiver also has automatic gain calibration,

this improves the precision of RSSI measurement and enhances image rejection.

5.5.2. Receiver Enabled and Receiver Active States

In the receiver operating mode two states of functionality are defined. Upon initial transition to receiver operating mode the

receiver is in the ‘receiver-enabled’ state. In this state the receiver awaits for either the user defined valid preamble or RSSI

detection criterion to be fulfilled. Once met the receiver enters ‘receiver-active’ state. In this second state the received

signal is processed by the packet engine and top level sequencer. For a complete description of the digital functions of the

SX1276/77/78/79 receiver please see section 4 of the datasheet.

5.5.3. Automatic Gain Control In FSK/OOK Mode

The AGC feature allows receiver to handle a wide Rx input dynamic range from the sensitivity level up to maximum input

level of 0dBm or more, whilst optimizing the system linearity.

The following table shows typical NF and IIP3 performances for the SX1276/77/78/79 LNA gains available.

OcpTrim IMAX Imax Formula

0 to 15 45 to 120 mA 45 + 5*OcpTrim [mA]

16 to 27 130 to 240 mA -30 + 10*OcpTrim [mA]

27+ 240 mA 240 mA

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Table 38 LNA Gain Control and Performances

5.5.4. RSSI in FSK/OOK Mode

The RSSI provides a measure of the incoming signal power at RF input port, measured within the receiver bandwidth. The

signal power is available in RssiValue. This value is absolute in units of dBm and with a resolution of 0.5 dB. The formula

below relates the register value to the absolute input signal level at the RF input port:

The RSSI value can be compensated to take into account the loss in the matching network or even the gain of an

additional LNA by using RssiOffset. The offset can be chosen in 1 dB steps from -16 to +15 dB. When compensation is

applied, the effective signal strength is read as follows:

The RSSI value is smoothed on a user defined number of measured RSSI samples. The precision of the RSSI value is

related to the number of RSSI samples used. RssiSmoothing selects the number of RSSI samples from a minimum of 2

samples up to 256 samples in increments of power of 2. Ta bl e 39 gives the estimation of the RSSI accuracy for a 10 dB

SNR and response time versus the number of RSSI samples programmed in RssiSmoothing.

Table 39 RssiSmoothing Options

The RSSI is calibrated when the image and RSSI calibration process is launched.

RX input level (Pin) Gain

Setting LnaGain Relative LNA

Gain [dB]

Band 3/2/1

[dB]

IIP3

Band 3/2/1

[dBm]

Pin <= AgcThresh1 G1 ‘001’ 0 dB 4/5.5/7 -15/-22/-11

AgcThresh1 < Pin <= AgcThresh2 G2 ‘010’ -6 dB 6.5/8/12 -11/-15/-6

AgcThresh2 < Pin <= AgcThresh3 G3 ‘011’ -12 dB 11/12/17 -11/-12/0

AgcThresh3 < Pin <= AgcThresh4 G4 ‘100’ -24 dB 20/21/27 2/3/9

AgcThresh4 < Pin <= AgcThresh5 G5 ‘110’ -26 dB 32/33/35 10/10/14

AgcThresh5 < Pin G6 ‘111’ -48 dB 44/45/43 11/12/14

RssiSmoothing Number of Samples Estimated Accuracy Response Time

‘000’ 2 ± 6 dB

‘001’ 4 ± 5 dB

‘010’ 8 ± 4 dB

‘011’ 16 ± 3 dB

‘100’ 32 ± 2 dB

‘101’ 64 ± 1.5 dB

‘110’ 128 ± 1.2 dB

‘111’ 256 ± 1.1 dB

[] []

dBRssiOffsetdBmlevelRFRssiValue

+⋅−=

[]

RssiValue

dBmRSSI −=

()

[]

kHzRxBw

ingRssiSmooth

⋅

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5.5.5. RSSI and SNR in LoRaTM Mode

The RSSI values reported by the LoRaTM modem differ from those expressed by the FSK/OOK modem. The following

formula shows the method used to interpret the LoRaTM RSSI values:

RSSI (dBm) = -157 + Rssi, (when using the High Frequency (HF) port)

RSSI (dBm) = -164 + Rssi, (when using the Low Frequency (LF) port)

The same formula can be re-used to evaluate the signal strength of the received packet:

Packet Strength (dBm) = -157 + Rssi, (when using the High Frequency (HF) port)

Packet Strength (dBm) = -164 + Rssi, (when using the Low Frequency (LF) port)

Due to the nature of the LoRa modulation, it is possible to receive packets below the noise floor. In this situation, the SNR

is used in conjunction of the PacketRssi to compute the signal strength of the received packet:

Packet Strength (dBm) = -157 + PacketRssi + PacketSnr * 0.25 (when using the HF port and SNR < 0)

Packet Strength (dBm) = -164 + PacketRssi + PacketSnr * 0.25 (when using the LF port and SNR < 0)

Note:

1. PacketRssi (in RegPktRssiValue), is an averaged version of Rssi (in RegRssiValue). Rssi can be read at any time

(during packet reception or not), and should be averaged to give more precise results.

2. The constants, -157 and -164, may vary with the front-end setup of the SX1276/77/78/79 (LnaBoost =1 or 0,

presence of an external LNA, mismatch at the LNA input…). It is recommended to adjust these values with a single-point

calibration procedure to increase RSSI accuracy.

3. As signal strength increases (RSSI>-100dBm), the linearity of PacketRssi is not guaranteed and results will diverge

from the ideal 1dB/dB ideal curve. When very good RSSI precision is required over the whole dynamic range of the

receiver, two options are proposed:

- Rssi in RegRssiValue offers better linearity. Rssi can be sampled during the reception of the payload (between

ValidHeader and RxDone IRQ), and used to extract a more high-signal RSSI measurement

- When SNR>=0, the standard formula can be adjusted to correct the slope:

RSSI = -157+16/15 * PacketRssi (or RSSI = -164+16/15 * PacketRssi)

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5.5.6. Channel Filter

The role of the channel filter is to reject noise and interference outside of the wanted channel. The SX1276/77/78/79

channel filtering is implemented with a 16-tap finite impulse response (FIR) filter. Rejection of the filter is high enough that

the filter stop-band performance is not the dominant influence on adjacent channel rejection performance. This is instead

limited by the SX1276/77/78/79 local oscillator phase noise.

Note To respect sampling criterion in the decimation chain of the receiver, the communication bit rate cannot be set at a

higher than twice the single side receiver bandwidth (BitRate < 2 x RxBw)

The single-side channel filter bandwidth RxBw is controlled by the parameters RxBwMant and RxBwExp in RegRxBw:

The following channel filter bandwidths are hence accessible in the case of a 32 MHz reference oscillator:

Table 40 Available RxBw Settings

RxBwMant

(binary/value)

RxBwExp

(decimal)

RxBw (kHz)

FSK/OOK

10b / 24 7 2.6

01b / 20 7 3.1

00b / 16 7 3.9

10b / 24 6 5.2

01b / 20 6 6.3

00b / 16 6 7.8

10b / 24 5 10.4

01b / 20 5 12.5

00b / 16 5 15.6

10b / 24 4 20.8

01b / 20 4 25.0

00b / 16 4 31.3

10b / 24 3 41.7

01b / 20 3 50.0

00b / 16 3 62.5

10b / 24 2 83.3

01b / 20 2 100.0

00b / 16 2 125.0

10b / 24 1 166.7

01b / 20 1 200.0

00b / 16 1 250.0

Other settings reserved

RxBw FXOSC

RxBwMant 2RxBwExp 2+

------------------------------------------------------------------

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5.5.7. Temperature Measurement

A stand alone temperature measurement block is used in order to measure the temperature in any mode except Sleep and

Standby. It is enabled by default, and can be stopped by setting TempMonitorOff to 1. The result of the measurement is

stored in TempValue in RegTemp.

Due to process variations, the absolute accuracy of the result is +/- 10 °C. Higher precision requires a calibration procedure

at a known temperature. The figure below shows the influence of just such a calibration process. For more information,

including source code, please consult the applications section of this document.

Figure 41. Temperature Sensor Response

When using the temperature sensor in the application, the following sequence should be followed:

Set the device to Standby and wait for oscillator startup

Set the device to FSRx mode

Set TempMonitorOff = 0 (enables the sensor). It is not required to wait for the PLL Lock indication

Wait for 140 microseconds

Set TempMonitorOff = 1

Set device back to Sleep of Standby mode

Access temperature value in RegTemp

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6. Description of the Registers

The register mapping depends upon whether FSK/OOK or LoRaTM mode has been selected. The following table

summarises the location and function of each register and gives an overview of the changes in register mapping between

both modes of operation.

6.1. Register Table Summary

Table 41 Registers Summary

Address

(POR)

Default

(FSK)

Description

FSK/OOK Mode LoRaTM Mode FSK Mode LoRaTM Mode

0x00 RegFifo 0x00 FIFO read/write access

0x01 RegOpMode 0x01 Operating mode & LoRaTM / FSK selection

0x02 RegBitrateMsb

Unused

0x1A Bit Rate setting, Most Significant Bits

0x03 RegBitrateLsb 0x0B Bit Rate setting, Least Significant Bits

0x04 RegFdevMsb 0x00 Frequency Deviation setting, Most Significant Bits

0x05 RegFdevLsb 0x52 Frequency Deviation setting, Least Significant Bits

0x06 RegFrfMsb 0x6C RF Carrier Frequency, Most Significant Bits

0x07 RegFrfMid 0x80 RF Carrier Frequency, Intermediate Bits

0x08 RegFrfLsb 0x00 RF Carrier Frequency, Least Significant Bits

0x09 RegPaConfig 0x4F PA selection and Output Power control

0x0A RegPaRamp 0x09 Control of PA ramp time, low phase noise PLL

0x0B RegOcp 0x2B Over Current Protection control

0x0C RegLna 0x20 LNA settings

0x0D RegRxConfig RegFifoAddrPtr 0x08 0x0E AFC, AGC, ctrl FIFO SPI pointer

0x0E RegRssiConfig RegFifoTxBa-

seAddr 0x02 RSSI Start Tx data

0x0F RegRssiCollision RegFifoRxBa-

seAddr 0x0A RSSI Collision detector Start Rx data

0x10 RegRssiThresh FifoRxCurren-

tAddr 0xFF RSSI Threshold control Start address of last

packet received

0x11 RegRssiValue RegIrqFlagsMask n/a n/a RSSI value in dBm Optional IRQ flag mask

0x12 RegRxBw RegIrqFlags 0x15 Channel Filter BW Control IRQ flags

0x13 RegAfcBw RegRxNbBytes 0x0B AFC Channel Filter BW Number of received bytes

0x14 RegOokPeak RegRxHeaderCnt

ValueMsb 0x28 OOK demodulator Number of valid headers

received

0x15 RegOokFix RegRxHeaderCnt

ValueLsb 0x0C Threshold of the OOK demod

0x16 RegOokAvg RegRxPacketCnt

ValueMsb 0x12 Average of the OOK demod Number of valid packets

received

0x17 Reserved17 RegRxPacketCnt

ValueLsb 0x47 -

0x18 Reserved18 RegModemStat 0x32 -Live LoRaTM modem

status

0x19 Reserved19 RegPktSnrValue 0x3E -Espimation of last packet

SNR

0x1A RegAfcFei RegPktRssiValue 0x00 AFC and FEI control RSSI of last packet

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0x1B RegAfcMsb RegRssiValue 0x00 n/a Frequency correction value of

the AFC

Current RSSI

0x1C RegAfcLsb RegHopChannel 0x00 n/a FHSS start channel

0x1D RegFeiMsb RegModemConfig

0x00 n/a

Value of the calculated

frequency error

Modem PHY config 1

0x1E RegFeiLsb RegModemConfig

0x00 n/a Modem PHY config 2

0x1F RegPreambleDe-

tect

RegSymbTimeout

Lsb

0x40 0xAA Settings of the Preamble

Detector Receiver timeout value

0x20 RegRxTimeout1 RegPreambleMsb 0x00 Timeout Rx request and RSSI

Size of preamble

0x21 RegRxTimeout2 RegPreambleLsb 0x00 Timeout RSSI and Pay-

loadReady

0x22 RegRxTimeout3 RegPay-

loadLength

0x00 Timeout RSSI and SyncAd-

dress LoRaTM payload length

0x23 RegRxDelay RegMaxPayloadL

ength

0x00 Delay between Rx cycles LoRaTM maximum pay-

load length

0x24 RegOsc RegHopPeriod 0x05 0x07 RC Oscillators Settings, CLK-

OUT frequency FHSS Hop period

0x25 RegPreambleMsb RegFifoRxByteAd

0x00 Preamble length, MSB Address of last byte

written in FIFO

0x26 RegPreambleLsb RegModemCon-

fig3

0x03 Preamble length, LSB Modem PHY config 3

0x27 RegSyncConfig RESERVED 0x93 Sync Word Recognition control RESERVED

0x28 RegSyncValue1 RegFeiMsb 0x55 0x01 Sync Word bytes 1

Estimated frequency

error

0x29 RegSyncValue2 RegFeiMid 0x55 0x01 Sync Word bytes 2

0x2A RegSyncValue3 RegFeiLsb 0x55 0x01 Sync Word bytes 3

0x2B RegSyncValue4 RESERVED 0x55 0x01 Sync Word bytes 4 RESERVED

0x2C RegSyncValue5 RegRssiWide-

band

0x55 0x01 Sync Word bytes 5 Wideband RSSI meas-

urement

0x2D-

0x2F

RegSyncValue6-8 RESERVED 0x55 0x01 Sync Word bytes, 6 to 8

RESERVED

0x30 RegPacketConfig1 RESERVED 0x90 Packet mode settings

0x31 RegPacketConfig2 RegDetectOpti-

mize

0x40 Packet mode settings LoRa detection Optimize

for SF6

0x32 RegPayloadLength RESERVED 0x40 Payload length setting RESERVED

0x33 RegNodeAdrs RegInvertIQ 0x00 Node address Invert LoRa I and Q

signals

0x34 RegBroadcastAdrs

RESERVED

0x00 Broadcast address

RESERVED

0x35 RegFifoThresh 0x0F 0x1F Fifo threshold, Tx start condi-

tion

0x36 RegSeqConfig1 0x00 Top level Sequencer settings

0x37 RegSeqConfig2 RegDetection-

Threshold

0x00 Top level Sequencer settings LoRa detection threshold

for SF6

0x38 RegTimerResol RESERVED 0x00 Timer 1 and 2 resolution control RESERVED

0x39 RegTimer1Coef RegSyncWord 0xF5 0x12 Timer 1 setting LoRa Sync Word

Address

(POR)

Default

(FSK)

Description

FSK/OOK Mode LoRaTM Mode FSK Mode LoRaTM Mode

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Note - Reset values are automatically refreshed in the chip at Power On Reset

- Default values are the Semtech recommended register values, optimizing the device operation

- Registers for which the Default value differs from the Reset value are denoted by a * in the tables of section 6.2

0x3A RegTimer2Coef

RESERVED

0x20 Timer 2 setting

RESERVED

0x3B RegImageCal 0x82 0x02 Image calibration engine con-

trol

0x3C RegTemp -Temperature Sensor value

0x3D RegLowBat 0x02 Low Battery Indicator Settings

0x3E RegIrqFlags1 0x80 Status register: PLL Lock state,

Timeout, RSSI

0x3F RegIrqFlags2 0x40 Status register: FIFO handling

flags, Low Battery

0x40 RegDioMapping1 0x00 Mapping of pins DIO0 to DIO3

0x41 RegDioMapping2 0x00 Mapping of pins DIO4 and DIO5, ClkOut frequency

0x42 RegVersion 0x12 Semtech ID relating the silicon revision

0x44 RegPllHop Unused 0x2D Control the fast frequency hop-

ping mode Unused

0x4B RegTcxo 0x09 TCXO or XTAL input setting

0x4D RegPaDac 0x84 Higher power settings of the PA

0x5B RegFormerTemp -Stored temperature during the former IQ Calibration

0x5D RegBitRateFrac Unused 0x00 Fractional part in the Bit Rate

division ratio Unused

0x61 RegAgcRef 0x13

Adjustment of the AGC thresholds

0x62 RegAgcThresh1 0x0E

0x63 RegAgcThresh2 0x5B

0x64 RegAgcThresh3 0xDB

0x70 RegPll 0xD0 Control of the PLL bandwidth

others RegTest -Internal test registers. Do not overwrite

Address

(POR)

Default

(FSK)

Description

FSK/OOK Mode LoRaTM Mode FSK Mode LoRaTM Mode

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6.2. FSK/OOK Mode Register Map

This section details the SX1276/77/78/79 register mapping and the precise contents of each register in FSK/OOK mode.

Convention: r: read, w: write, t:trigger, c: clear

Table 42 Register Map

Name

(Address) Bits Variable Name Mode Default

value FSK/OOK Description

RegFifo

(0x00) 7-0 Fifo rw 0x00 FIFO data input/output

Registers for Common settings

RegOpMode

(0x01)

7LongRangeMode r 0x00

0  FSK/OOK Mode

1 LoRaTM Mode

This bit can be modified only in Sleep mode. A write operation on

other device modes is ignored.

6-5 ModulationType rw 0x00

Modulation scheme:

00  FSK

01  OOK

10  11  reserved

4reserved r 0x0 reserved

3LowFrequencyModeOn rw 0x01

Access Low Frequency Mode registers (from address 0x61 on)

0  High Frequency Mode (access to HF test registers)

1  Low Frequency Mode (access to LF test registers)

2-0 Mode rw 0x01

Transceiver modes

000  Sleep mode

001  Stdby mode

010  FS mode TX (FSTx)

011  Transmitter mode (Tx)

100  FS mode RX (FSRx)

101  Receiver mode (Rx)

110  reserved

111  reserved

RegBitrateMsb

(0x02) 7-0 BitRate(15:8) rw 0x1a MSB of Bit Rate (chip rate if Manchester encoding is enabled)

RegBitrateLsb

(0x03) 7-0 BitRate(7:0) rw 0x0b

LSB of bit rate (chip rate if Manchester encoding is enabled)

Default value: 4.8 kb/s

RegFdevMsb

(0x04)

7-6 reserved rw 0x00 reserved

5-0 Fdev(13:8) rw 0x00 MSB of the frequency deviation

RegFdevLsb

(0x05) 7-0 Fdev(7:0) rw 0x52

LSB of the frequency deviation

Default value: 5 kHz

BitRate FXOSC

BitRate 15 0(,)BitrateFrac

-------------------------------

-------------------------------------------------------------------------

Fdev Fstep Fdev 15 0(,)×=

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RegFrfMsb

(0x06) 7-0 Frf(23:16) rw 0x6c MSB of the RF carrier frequency

RegFrfMid

(0x07) 7-0 Frf(15:8) rw 0x80 MSB of the RF carrier frequency

RegFrfLsb

(0x08) 7-0 Frf(7:0) rw 0x00

LSB of RF carrier frequency

Default value: 434.000 MHz

The RF frequency is taken into account internally only when:

- entering FSRX/FSTX modes

- re-starting the receiver

Registers for the Transmitter

RegPaConfig

(0x09)

7PaSelect rw 0x00

Selects PA output pin

0  RFO pin. Maximum power of +14 dBm

1  PA_BOOST pin. Maximum power of +20 dBm

6-4 MaxPower rw 0x04 Select max output power: Pmax=10.8+0.6*MaxPower [dBm]

3-0 OutputPower rw 0x0f Pout=Pmax-(15-OutputPower) if PaSelect = 0 (RFO pins)

Pout=17-(15-OutputPower) if PaSelect = 1 (PA_BOOST pin)

RegPaRamp

(0x0A)

7unused r 0x00 unused

6-5 ModulationShaping rw 0x00

Data shaping:

In FSK:

00  no shaping

01  Gaussian filter BT = 1.0

10  Gaussian filter BT = 0.5

11  Gaussian filter BT = 0.3

In OOK:

00  no shaping

01  filtering with fcutoff = bit_rate

10  filtering with fcutoff = 2*bit_rate (for bit_rate < 125 kb/s)

11  reserved

4reserved rw 0x00 reserved

3-0 PaRamp rw 0x09

Rise/Fall time of ramp up/down in FSK

0000  3.4 ms

0001  2 ms

0010  1 ms

0011  500 us

0100  250 us

0101  125 us

0110  100 us

0111  62 us

1000  50 us

1001  40 us (d)

1010  31 us

1011  25 us

1100  20 us

1101  15 us

1110  12 us

1111  10 us

Name

(Address) Bits Variable Name Mode Default

value FSK/OOK Description

Frf Fstep Frf 23 0;()×=

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RegOcp

(0x0B)

7-6 unused r 0x00 unused

5OcpOn rw 0x01

Enables overload current protection (OCP) for the PA:

0  OCP disabled

1  OCP enabled

4-0 OcpTrim rw 0x0b

Trimming of OCP current:

Imax = 45+5*OcpTrim [mA] if OcpTrim <= 15 (120 mA) /

Imax = -30+10*OcpTrim [mA] if 15 < OcpTrim <= 27 (130 to 240

mA)

Imax = 240mA for higher settings

Default Imax = 100mA

Registers for the Receiver

RegLna

(0x0C)

7-5 LnaGain rw 0x01

LNA gain setting:

000  reserved

001  G1 = highest gain

010  G2 = highest gain – 6 dB

011  G3 = highest gain – 12 dB

100  G4 = highest gain – 24 dB

101  G5 = highest gain – 36 dB

110  G6 = highest gain – 48 dB

111  reserved

Note:

Reading this address always returns the current LNA gain (which

may be different from what had been previously selected if AGC

is enabled.

4-3 LnaBoostLf rw 0x00

Low Frequency (RFI_LF) LNA current adjustment

00  Default LNA current

Other  Reserved

2reserved rw 0x00 reserved

1-0 LnaBoostHf rw 0x00

High Frequency (RFI_HF) LNA current adjustment

00  Default LNA current

11  Boost on, 150% LNA current

Name

(Address) Bits Variable Name Mode Default

value FSK/OOK Description

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RegRxConfig

(0x0d)

7RestartRxOnCollision rw 0x00

Turns on the mechanism restarting the receiver automatically if it

gets saturated or a packet collision is detected

0  No automatic Restart

1  Automatic restart On

6RestartRxWithoutPllLock wt 0x00

Triggers a manual Restart of the Receiver chain when set to 1.

Use this bit when there is no frequency change,

RestartRxWithPllLock otherwise.

5RestartRxWithPllLock wt 0x00

Triggers a manual Restart of the Receiver chain when set to 1.

Use this bit when there is a frequency change, requiring some

time for the PLL to re-lock.

4AfcAutoOn rw 0x00 0  No AFC performed at receiver startup

1  AFC is performed at each receiver startup

3AgcAutoOn rw 0x01 0  LNA gain forced by the LnaGain Setting

1  LNA gain is controlled by the AGC

2-0 RxTrigger rw 0x06

Selects the event triggering AGC and/or AFC at receiver startup.

See Table 24 for a description.

RegRssiConfig

(0x0e)

7-3 RssiOffset rw 0x00

Signed RSSI offset, to compensate for the possible losses/gains

in the front-end (LNA, SAW filter...)

1dB / LSB, 2’s complement format

2-0 RssiSmoothing rw 0x02

Defines the number of samples taken to average the RSSI result:

000  2 samples used

001  4 samples used

010  8 samples used

011  16 samples used

100  32 samples used

101  64 samples used

110  128 samples used

111  256 samples used

RegRssiCollision

(0x0f) 7-0 RssiCollisionThreshold rw 0x0a

Sets the threshold used to consider that an interferer is detected,

witnessing a packet collision. 1dB/LSB (only RSSI increase)

Default: 10dB

RegRssiThresh

(0x10) 7-0 RssiThreshold rw 0xff RSSI trigger level for the Rssi interrupt:

- RssiThreshold / 2 [dBm]

RegRssiValue

(0x11) 7-0 RssiValue r - Absolute value of the RSSI in dBm, 0.5dB steps.

RSSI = - RssiValue/2 [dBm]

RegRxBw

(0x12)

7unused r - unused

6-5 reserved rw 0x00 reserved

4-3 RxBwMant rw 0x02

Channel filter bandwidth control:

00  RxBwMant = 16 10  RxBwMant = 24

01  RxBwMant = 20 11  reserved

2-0 RxBwExp rw 0x05 Channel filter bandwidth control

RegAfcBw

(0x13)

7-5 reserved rw 0x00 reserved

4-3 RxBwMantAfc rw 0x01 RxBwMant parameter used during the AFC

2-0 RxBwExpAfc rw 0x03 RxBwExp parameter used during the AFC

Name

(Address) Bits Variable Name Mode Default

value FSK/OOK Description

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RegOokPeak

(0x14)

7-6 reserved rw 0x00 reserved

5BitSyncOn rw 0x01

Enables the Bit Synchronizer.

0  Bit Sync disabled (not possible in Packet mode)

1  Bit Sync enabled

4-3 OokThreshType rw 0x01

Selects the type of threshold in the OOK data slicer:

00  fixed threshold 10  average mode

01  peak mode (default) 11  reserved

2-0 OokPeakTheshStep rw 0x00

Size of each decrement of the RSSI threshold in the OOK

demodulator:

000  0.5 dB 001  1.0 dB

010  1.5 dB 011  2.0 dB

100  3.0 dB 101  4.0 dB

110  5.0 dB 111  6.0 dB

RegOokFix

(0x15) 7-0 OokFixedThreshold rw 0x0C

Fixed threshold for the Data Slicer in OOK mode

Floor threshold for the Data Slicer in OOK when Peak mode is

used

RegOokAvg

(0x16)

7-5 OokPeakThreshDec rw 0x00

Period of decrement of the RSSI threshold in the OOK

demodulator:

000  once per chip 001  once every 2 chips

010  once every 4 chips 011  once every 8 chips

100  twice in each chip 101  4 times in each chip

110  8 times in each chip 111  16 times in each chip

4reserved rw 0x01 reserved

3-2 OokAverageOffset rw 0x00

Static offset added to the threshold in average mode in order to

reduce glitching activity (OOK only):

00  0.0 dB 10  4.0 dB

01  2.0 dB 11  6.0 dB

1-0 OokAverageThreshFilt rw 0x02

Filter coefficients in average mode of the OOK demodulator:

00  fC ≈ chip rate / 32.π 01  fC ≈ chip rate / 8.π

10  fC ≈ chip rate / 4.π 11 fC ≈ chip rate / 2.π

RegRes17

RegRes19

7-0 reserved rw

0x47

0x32

0x3E

reserved. Keep the Reset values.

RegAfcFei

(0x1a)

7-5 unused r - unused

4AgcStart wt 0x00 Triggers an AGC sequence when set to 1.

3reserved rw 0x00 reserved

2unused - - unused

1AfcClear wc 0x00 Clear AFC register set in Rx mode. Always reads 0.

0AfcAutoClearOn rw 0x00

Only valid if AfcAutoOn is set

0  AFC register is not cleared at the beginning of the automatic

AFC phase

1  AFC register is cleared at the beginning of the automatic

AFC phase

Name

(Address) Bits Variable Name Mode Default

value FSK/OOK Description

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RegAfcMsb

(0x1b) 7-0 AfcValue(15:8) rw 0x00 MSB of the AfcValue, 2’s complement format. Can be used to

overwrite the current AFC value

RegAfcLsb

(0x1c) 7-0 AfcValue(7:0) rw 0x00 LSB of the AfcValue, 2’s complement format. Can be used to

overwrite the current AFC value

RegFeiMsb

(0x1d) 7-0 FeiValue(15:8) rw - MSB of the measured frequency offset, 2’s complement. Must be

read before RegFeiLsb.

RegFeiLsb

(0x1e) 7-0 FeiValue(7:0) rw - LSB of the measured frequency offset, 2’s complement

Frequency error = FeiValue x Fstep

RegPreambleDetect

(0x1f)

7PreambleDetectorOn rw 0x01

Enables Preamble detector when set to 1. The AGC settings

supersede this bit during the startup / AGC phase.

0  Turned off

1  Turned on

6-5 PreambleDetectorSize rw 0x01

Number of Preamble bytes to detect to trigger an interrupt

00  1 byte 10  3 bytes

01  2 bytes 11  Reserved

4-0 PreambleDetectorTol rw 0x0A

Number or chip errors tolerated over PreambleDetectorSize.

4 chips per bit.

RegRxTimeout1

(0x20) 7-0 TimeoutRxRssi rw 0x00

Timeout interrupt is generated TimeoutRxRssi*16*Tbit after

switching to Rx mode if Rssi interrupt doesn’t occur (i.e.

RssiValue > RssiThreshold)

0x00: TimeoutRxRssi is disabled

RegRxTimeout2

(0x21) 7-0 TimeoutRxPreamble rw 0x00

Timeout interrupt is generated TimeoutRxPreamble*16*Tbit after

switching to Rx mode if Preamble interrupt doesn’t occur

0x00: TimeoutRxPreamble is disabled

RegRxTimeout3

(0x22) 7-0 TimeoutSignalSync rw 0x00

Timeout interrupt is generated TimeoutSignalSync*16*Tbit after

the Rx mode is programmed, if SyncAddress doesn’t occur

0x00: TimeoutSignalSync is disabled

RegRxDelay

(0x23) 7-0 InterPacketRxDelay rw 0x00 Additional delay before an automatic receiver restart is launched:

Delay = InterPacketRxDelay*4*Tbit

RC Oscillator registers

RegOsc

(0x24)

7-4 unused r - unused

3RcCalStart wt 0x00 Triggers the calibration of the RC oscillator when set. Always

reads 0. RC calibration must be triggered in Standby mode.

2-0 ClkOut rw 0x07

Selects CLKOUT frequency:

000  FXOSC

001  FXOSC / 2

010  FXOSC / 4

011  FXOSC / 8

100  FXOSC / 16

101  FXOSC / 32

110  RC (automatically enabled)

111  OFF

Packet Handling registers

Name

(Address) Bits Variable Name Mode Default

value FSK/OOK Description

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RegPreambleMsb

(0x25) 7-0 PreambleSize(15:8) rw 0x00 Size of the preamble to be sent (from TxStartCondition fulfilled).

(MSB byte)

RegPreambleLsb

(0x26) 7-0 PreambleSize(7:0) rw 0x03 Size of the preamble to be sent (from TxStartCondition fulfilled).

(LSB byte)

RegSyncConfig

(0x27)

7-6 AutoRestartRxMode rw 0x02

Controls the automatic restart of the receiver after the reception of

a valid packet (PayloadReady or CrcOk):

00  Off

01  On, without waiting for the PLL to re-lock

10  On, wait for the PLL to lock (frequency changed)

11  reserved

5PreamblePolarity rw 0x00

Sets the polarity of the Preamble

0  0xAA (default)

1  0x55

4 SyncOn rw 0x01

Enables the Sync word generation and detection:

0  Off

1  On

3reserved rw 0x00 reserved

2-0 SyncSize rw 0x03 Size of the Sync word:

(SyncSize + 1) bytes, (SyncSize) bytes if ioHomeOn=1

RegSyncValue1

(0x28) 7-0 SyncValue(63:56) rw 0x01

1st byte of Sync word. (MSB byte)

Used if SyncOn is set.

RegSyncValue2

(0x29) 7-0 SyncValue(55:48) rw 0x01

2nd byte of Sync word

Used if SyncOn is set and (SyncSize +1) >= 2.

RegSyncValue3

(0x2a) 7-0 SyncValue(47:40) rw 0x01

3rd byte of Sync word.

Used if SyncOn is set and (SyncSize +1) >= 3.

RegSyncValue4

(0x2b) 7-0 SyncValue(39:32) rw 0x01

4th byte of Sync word.

Used if SyncOn is set and (SyncSize +1) >= 4.

RegSyncValue5

(0x2c) 7-0 SyncValue(31:24) rw 0x01

5th byte of Sync word.

Used if SyncOn is set and (SyncSize +1) >= 5.

RegSyncValue6

(0x2d) 7-0 SyncValue(23:16) rw 0x01

6th byte of Sync word.

Used if SyncOn is set and (SyncSize +1) >= 6.

RegSyncValue7

(0x2e) 7-0 SyncValue(15:8) rw 0x01

7th byte of Sync word.

Used if SyncOn is set and (SyncSize +1) >= 7.

RegSyncValue8

(0x2f) 7-0 SyncValue(7:0) rw 0x01

8th byte of Sync word.

Used if SyncOn is set and (SyncSize +1) = 8.

Name

(Address) Bits Variable Name Mode Default

value FSK/OOK Description

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RegPacketConfig1

(0x30)

7PacketFormat rw 0x01

Defines the packet format used:

0  Fixed length

1  Variable length

6-5 DcFree rw 0x00

Defines DC-free encoding/decoding performed:

00  None (Off)

01  Manchester

10  Whitening

11  reserved

4CrcOn rw 0x01

Enables CRC calculation/check (Tx/Rx):

0  Off

1  On

3CrcAutoClearOff rw 0x00

Defines the behavior of the packet handler when CRC check fails:

0  Clear FIFO and restart new packet reception. No

PayloadReady interrupt issued.

1  Do not clear FIFO. PayloadReady interrupt issued.

2-1 AddressFiltering rw 0x00

Defines address based filtering in Rx:

00  None (Off)

01  Address field must match NodeAddress

10  Address field must match NodeAddress or

BroadcastAddress

11  reserved

0CrcWhiteningType rw 0x00

Selects the CRC and whitening algorithms:

0  CCITT CRC implementation with standard whitening

1  IBM CRC implementation with alternate whitening

RegPacketConfig2

(0x31)

7unused r - unused

6DataMode rw 0x01

Data processing mode:

0  Continuous mode

1  Packet mode

5IoHomeOn rw 0x00

Enables the io-homecontrol® compatibility mode

0  Disabled

1  Enabled

4IoHomePowerFrame rw 0x00 reserved - Linked to io-homecontrol® compatibility mode

3BeaconOn rw 0x00 Enables the Beacon mode in Fixed packet format

2-0 PayloadLength(10:8) rw 0x00 Packet Length Most significant bits

RegPayloadLength

(0x32) 7-0 PayloadLength(7:0) rw 0x40 If PacketFormat = 0 (fixed), payload length.

If PacketFormat = 1 (variable), max length in Rx, not used in Tx.

RegNodeAdrs

(0x33) 7-0 NodeAddress rw 0x00 Node address used in address filtering.

RegBroadcastAdrs

(0x34) 7-0 BroadcastAddress rw 0x00 Broadcast address used in address filtering.

Name

(Address) Bits Variable Name Mode Default

value FSK/OOK Description

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RegFifoThresh

(0x35)

7TxStartCondition rw 0x01

Defines the condition to start packet transmission:

0  FifoLevel (i.e. the number of bytes in the FIFO exceeds

FifoThreshold)

1  FifoEmpty goes low(i.e. at least one byte in the FIFO)

6unused r - unused

5-0 FifoThreshold rw 0x0f Used to trigger FifoLevel interrupt, when:

number of bytes in FIFO >= FifoThreshold + 1

Sequencer registers

RegSeqConfig1

(0x36)

7SequencerStart wt 0x00

Controls the top level Sequencer

When set to ‘1’, executes the “Start” transition.

The sequencer can only be enabled when the chip is in Sleep or

Standby mode.

6SequencerStop wt 0x00 Forces the Sequencer Off.

Always reads ‘0’

5IdleMode rw 0x00

Selects chip mode during the state:

0: Standby mode

1: Sleep mode

4-3 FromStart rw 0x00

Controls the Sequencer transition when SequencerStart is set to 1

in Sleep or Standby mode:

00: to LowPowerSelection

01: to Receive state

10: to Transmit state

11: to Transmit state on a FifoLevel interrupt

2LowPowerSelection rw 0x00

Selects the Sequencer LowPower state after a to

LowPowerSelection transition:

0: SequencerOff state with chip on Initial mode

1: Idle state with chip on Standby or Sleep mode depending on

IdleMode

Note: Initial mode is the chip LowPower mode at

Sequencer Start.

1FromIdle rw 0x00

Controls the Sequencer transition from the Idle state on a T1

interrupt:

0: to Transmit state

1: to Receive state

0FromTransmit rw 0x00

Controls the Sequencer transition from the Transmit state:

0: to LowPowerSelection on a PacketSent interrupt

1: to Receive state on a PacketSent interrupt

Name

(Address) Bits Variable Name Mode Default

value FSK/OOK Description

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RegSeqConfig2

(0x37)

7-5 FromReceive rw 0x00

Controls the Sequencer transition from the Receive state

000 and 111: unused

001: to PacketReceived state on a PayloadReady interrupt

010: to LowPowerSelection on a PayloadReady interrupt

011: to PacketReceived state on a CrcOk interrupt (1)

100: to SequencerOff state on a Rssi interrupt

101: to SequencerOff state on a SyncAddress interrupt

110: to SequencerOff state on a PreambleDetect interrupt

Irrespective of this setting, transition to LowPowerSelection on a

T2 interrupt

(1) If the CRC is wrong (corrupted packet, with CRC on but

CrcAutoClearOn=0), the PayloadReady interrupt will drive the

sequencer to RxTimeout state.

4-3 FromRxTimeout rw 0x00

Controls the state-machine transition from the Receive state on a

RxTimeout interrupt (and on PayloadReady if FromReceive =

011):

00: to Receive State, via ReceiveRestart

01: to Transmit state

10: to LowPowerSelection

11: to SequencerOff state

Note: RxTimeout interrupt is a TimeoutRxRssi,

TimeoutRxPreamble or TimeoutSignalSync interrupt

2-0 FromPacketReceived rw 0x00

Controls the state-machine transition from the PacketReceived

state:

000: to SequencerOff state

001: to Transmit state on a FifoEmpty interrupt

010: to LowPowerSelection

011: to Receive via FS mode, if frequency was changed

100: to Receive state (no frequency change)

RegTimerResol

(0x38)

7-4 unused r - unused

3-2 Timer1Resolution rw 0x00

Resolution of Timer 1

00: Timer1 disabled

01: 64 us

10: 4.1 ms

11: 262 ms

1-0 Timer2Resolution rw 0x00

Resolution of Timer 2

00: Timer2 disabled

01: 64 us

10: 4.1 ms

11: 262 ms

RegTimer1Coef

(0x39) 7-0 Timer1Coefficient rw 0xf5 Multiplying coefficient for Timer 1

RegTimer2Coef

(0x3a) 7-0 Timer2Coefficient rw 0x20 Multiplying coefficient for Timer 2

Name

(Address) Bits Variable Name Mode Default

value FSK/OOK Description

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Service registers

RegImageCal

(0x3b)

7AutoImageCalOn rw 0x00

Controls the Image calibration mechanism

0  Calibration of the receiver depending on the temperature is

disabled

1  Calibration of the receiver depending on the temperature

enabled.

6ImageCalStart wt - Triggers the IQ and RSSI calibration when set in Standby mode.

5ImageCalRunning r 0x00 Set to 1 while the Image and RSSI calibration are running.

Toggles back to 0 when the process is completed

4unused r - unused

3TempChange r 0x00

IRQ flag witnessing a temperature change exceeding

TempThreshold since the last Image and RSSI calibration:

0  Temperature change lower than TempThreshold

1  Temperature change greater than TempThreshold

2-1 TempThreshold rw 0x01

Temperature change threshold to trigger a new I/Q calibration

00  5 °C

01  10 °C

10  15 °C

11  20 °C

0TempMonitorOff rw 0x00

Controls the temperature monitor operation:

0  Temperature monitoring done in all modes except Sleep and

Standby

1  Temperature monitoring stopped.

RegTemp

(0x3c) 7-0 Te m p Va l u e r -

Measured temperature

-1°C per Lsb

Needs calibration for absolute accuracy

RegLowBat

(0x3d)

7-4 unused r - unused

3LowBatOn rw 0x00

Low Battery detector enable signal

0  LowBat detector disabled

1  LowBat detector enabled

2-0 LowBatTrim rw 0x02

Trimming of the LowBat threshold:

000  1.695 V

001  1.764 V

010  1.835 V (d)

011  1.905 V

100  1.976 V

101  2.045 V

110  2.116 V

111  2.185 V

Status registers

Name

(Address) Bits Variable Name Mode Default

value FSK/OOK Description

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RegIrqFlags1

(0x3e)

7ModeReady r -

Set when the operation mode requested in Mode, is ready

- Sleep: Entering Sleep mode

- Standby: XO is running

- FS: PLL is locked

- Rx: RSSI sampling starts

- Tx: PA ramp-up completed

Cleared when changing the operating mode.

6RxReady r - Set in Rx mode, after RSSI, AGC and AFC.

Cleared when leaving Rx.

5TxReady r - Set in Tx mode, after PA ramp-up.

Cleared when leaving Tx.

4PllLock r - Set (in FS, Rx or Tx) when the PLL is locked.

Cleared when it is not.

3Rssi rwc - Set in Rx when the RssiValue exceeds RssiThreshold.

Cleared when leaving Rx or setting this bit to 1.

2Timeout r - Set when a timeout occurs

Cleared when leaving Rx or FIFO is emptied.

1PreambleDetect rwc - Set when the Preamble Detector has found valid Preamble.

bit clear when set to 1

0SyncAddressMatch rwc -

Set when Sync and Address (if enabled) are detected.

Cleared when leaving Rx or FIFO is emptied.

This bit is read only in Packet mode, rwc in Continuous mode

RegIrqFlags2

(0x3f)

7FifoFull r - Set when FIFO is full (i.e. contains 66 bytes), else cleared.

6FifoEmpty r - Set when FIFO is empty, and cleared when there is at least 1 byte

in the FIFO.

5FifoLevel r - Set when the number of bytes in the FIFO strictly exceeds

FifoThreshold, else cleared.

4FifoOverrun rwc -

Set when FIFO overrun occurs. (except in Sleep mode)

Flag(s) and FIFO are cleared when this bit is set. The FIFO then

becomes immediately available for the next transmission /

reception.

3PacketSent r - Set in Tx when the complete packet has been sent.

Cleared when exiting Tx

2PayloadReady r -

Set in Rx when the payload is ready (i.e. last byte received and

CRC, if enabled and CrcAutoClearOff is cleared, is Ok). Cleared

when FIFO is empty.

1CrcOk r - Set in Rx when the CRC of the payload is Ok. Cleared when FIFO

is empty.

0LowBat rwc - Set when the battery voltage drops below the Low Battery

threshold. Cleared only when set to 1 by the user.

IO control registers

Name

(Address) Bits Variable Name Mode Default

value FSK/OOK Description

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RegDioMapping1

(0x40)

7-6 Dio0Mapping rw 0x00

Mapping of pins DIO0 to DIO5

See Table 18 for mapping in LoRa mode

See Table 29 for mapping in Continuous mode

SeeTable 30 for mapping in Packet mode

5-4 Dio1Mapping rw 0x00

3-2 Dio2Mapping rw 0x00

1-0 Dio3Mapping rw 0x00

RegDioMapping2

(0x41)

7-6 Dio4Mapping rw 0x00

5-4 Dio5Mapping rw 0x00

3-1 reserved rw 0x00 reserved. Retain default value

0MapPreambleDetect rw 0x00

Allows the mapping of either Rssi Or PreambleDetect to the DIO

pins, as summarized on Table 29 and Table 30

0  Rssi interrupt

1  PreambleDetect interrupt

Version register

RegVersion

(0x42) 7-0 Version r 0x12 Version code of the chip. Bits 7-4 give the full revision number;

bits 3-0 give the metal mask revision number.

Additional registers

RegPllHop

(0x44)

7FastHopOn rw 0x00

Bypasses the main state machine for a quick frequency hop.

Writing RegFrfLsb will trigger the frequency change.

0  Frf is validated when FSTx or FSRx is requested

1  Frf is validated triggered when RegFrfLsb is written

6-0 reserved rw 0x2d reserved

RegTcxo

(0x4b)

7-5 reserved rw 0x00 reserved. Retain default value

4TcxoInputOn rw 0x00

Controls the crystal oscillator

0  Crystal Oscillator with external Crystal

1  External clipped sine TCXO AC-connected to XTA pin

3-0 reserved rw 0x09 Reserved. Retain default value.

RegPaDac

(0x4d)

7-3 reserved rw 0x10 reserved. Retain default value

2-0 PaDac rw 0x04

Enables the +20dBm option on PA_BOOST pin

0x04  Default value

0x07  +20dBm on PA_BOOST when OutputPower=1111

RegFormerTemp

(0x5b) 7-0 FormerTemp rw - Temperature saved during the latest IQ (RSSI and Image)

calibration. Same format as TempValue in RegTemp.

RegBitrateFrac

(0x5d)

7-4 unused r 0x00 unused

3-0 BitRateFrac rw 0x00

Fractional part of the bit rate divider (Only valid for FSK)

If BitRateFrac> 0 then:

Name

(Address) Bits Variable Name Mode Default

value FSK/OOK Description

BitRate FXOSC

BitRate 15 0(,)BitrateFrac

-------------------------------

-------------------------------------------------------------------------

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6.3. Band Specific Additional Registers

The registers in the address space from 0x61 to 0x73 are specific for operation in the lower frequency bands (below 525

MHz), or in the upper frequency bands (above 779 MHz). Their programmed value may differ, and are retained when

switching from lower to high frequency and vice-versa. The access to the band specific registers is granted by enabling or

disabling the bit 3 LowFrequencyModeOn of the RegOpMode register. By default, the bit LowFrequencyModeOn is at ‘1’

indicating that the registers are configured for the low frequency band.

Table 43 Low Frequency Additional Registers

RegAgcRef

(0x61)

7-6 unused r - unused

5-0 AgcReferenceLevel rw 0x19

Sets the floor reference for all AGC thresholds:

AGC Reference[dBm]=

-174dBm+10*log(2*RxBw)+SNR+AgcReferenceLevel

SNR = 8dB, fixed value

RegAgcThresh1

(0x62)

7-5 unused r - unused

4-0 AgcStep1 rw 0x0c Defines the 1st AGC Threshold

RegAgcThresh2

(0x63)

7-4 AgcStep2 rw 0x04 Defines the 2nd AGC Threshold:

3-0 AgcStep3 rw 0x0b Defines the 3rd AGC Threshold:

RegAgcThresh3

(0x64)

7-4 AgcStep4 rw 0x0c Defines the 4th AGC Threshold:

3-0 AgcStep5 rw 0x0c Defines the 5th AGC Threshold:

Name

(Address) Bits Variable Name Mode Default

value Low Frequency Additional Registers

RegAgcRefLf

(0x61)

7-6 unused r - unused

5-0 AgcReferenceLevel rw 0x19

Sets the floor reference for all AGC thresholds:

AGC Reference[dBm]=

-174dBm+10*log(2*RxBw)+SNR+AgcReferenceLevel

SNR = 8dB, fixed value

RegAgcThresh1Lf

(0x62)

7-5 unused r - unused

4-0 AgcStep1 rw 0x0c Defines the 1st AGC Threshold

RegAgcThresh2Lf

(0x63)

7-4 AgcStep2 rw 0x04 Defines the 2nd AGC Threshold:

3-0 AgcStep3 rw 0x0b Defines the 3rd AGC Threshold:

RegAgcThresh3Lf

(0x64)

7-4 AgcStep4 rw 0x0c Defines the 4th AGC Threshold:

3-0 AgcStep5 rw 0x0c Defines the 5th AGC Threshold:

RegPllLf

(0x70)

7-6 PllBandwidth rw 0x03

Controls the PLL bandwidth:

00  75 kHz 10  225 kHz

01  150 kHz 11  300 kHz

5-0 reserved rw 0x10 reserved. Retain default value

Name

(Address) Bits Variable Name Mode Default

value FSK/OOK Description

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Table 44 High Frequency Additional Registers

Name

(Address) Bits Variable Name Mode Default

value Low Frequency Additional Registers

RegAgcRefHf

(0x61)

7-6 unused r - unused

5-0 AgcReferenceLevel rw 0x1c

Sets the floor reference for all AGC thresholds:

AGC Reference[dBm]=

-174dBm+10*log(2*RxBw)+SNR+AgcReferenceLevel

SNR = 8dB, fixed value

RegAgcThresh1Hf

(0x62)

7-5 unused r - unused

4-0 AgcStep1 rw 0x0e Defines the 1st AGC Threshold

RegAgcThresh2Hf

(0x63)

7-4 AgcStep2 rw 0x05 Defines the 2nd AGC Threshold:

3-0 AgcStep3 rw 0x0b Defines the 3rd AGC Threshold:

RegAgcThresh3Hf

(0x64)

7-4 AgcStep4 rw 0x0c Defines the 4th AGC Threshold:

3-0 AgcStep5 rw 0x0c Defines the 5th AGC Threshold:

RegPllHf

(0x70)

7-6 PllBandwidth rw 0x03

Controls the PLL bandwidth:

00  75 kHz 10  225 kHz

01  150 kHz 11  300 kHz

5-0 reserved rw 0x10 reserved. Retain default value

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6.4. LoRaTM Mode Register Map

This details the SX1276/77/78/79 register mapping and the precise contents of each register in LoRaTM mode.

It is essential to understand that the LoRaTM modem is controlled independently of the FSK modem. Therefore, care

should be taken when accessing the registers, especially as some register may have the same name in LoRaTM or FSK

mode.

The LoRa registers are only accessible when the device is set in Lora mode (and, in the same way, the FSK register are

only accessible in FSK mode). However, in some cases, it may be necessary to access some of the FSK register while in

LoRa mode. To this aim, the AccesSharedReg bit was created in the RegOpMode register. This bit, when set to ‘1’, will

grant access to the FSK register 0x0D up to the register 0x3F. Once the setup has been done, it is strongly recommended

to clear this bit so that LoRa register can be accessed normally.

Convention: r: read, w: write, c : set to clear and t: trigger.

Name

(Address) Bits Variable Name Mode Reset LoRaTM Description

RegFifo

(0x00) 7-0 Fifo rw 0x00 LoRaTM base-band FIFO data input/output. FIFO is cleared an

not accessible when device is in SLEEP mode

Common Register Settings

RegOpMode

(0x01)

7LongRangeMode rw 0x0

0  FSK/OOK Mode

1  LoRaTM Mode

This bit can be modified only in Sleep mode. A write operation on

other device modes is ignored.

6AccessSharedReg rw 0x0

This bit operates when device is in Lora mode; if set it allows

access to FSK registers page located in address space

(0x0D:0x3F) while in LoRa mode

0  Access LoRa registers page 0x0D: 0x3F

1  Access FSK registers page (in mode LoRa) 0x0D: 0x3F

5-4 reserved r 0x00 reserved

3LowFrequencyModeOn rw 0x01

Access Low Frequency Mode registers

0  High Frequency Mode (access to HF test registers)

1  Low Frequency Mode (access to LF test registers)

2-0 Mode rwt 0x01

Device modes

000  SLEEP

001  STDBY

010  Frequency synthesis TX (FSTX)

011  Transmit (TX)

100  Frequency synthesis RX (FSRX)

101  Receive continuous (RXCONTINUOUS)

110  receive single (RXSINGLE)

111  Channel activity detection (CAD)

(0x02) 7-0 reserved r 0x00 -

(0x03) 7-0 reserved r 0x00 -

(0x04) 7-0 reserved rw 0x00 -

(0x05) 7-0 reserved r 0x00 -

RegFrMsb

(0x06) 7-0 Frf(23:16) rw 0x6c MSB of RF carrier frequency

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RegFrMid

(0x07) 7-0 Frf(15:8) rw 0x80 MSB of RF carrier frequency

RegFrLsb

(0x08) 7-0 Frf(7:0) rwt 0x00

LSB of RF carrier frequency

Resolution is 61.035 Hz if F(XOSC) = 32 MHz. Default value is

0x6c8000 = 434 MHz. Register values must be modified only

when device is in SLEEP or STAND-BY mode.

Registers for RF blocks

RegPaConfig

(0x09)

7PaSelect rw 0x00

Selects PA output pin

0  RFO pin. Output power is limited to +14 dBm.

1  PA_BOOST pin. Output power is limited to +20 dBm

6-4 MaxPower rw 0x04 Select max output power: Pmax=10.8+0.6*MaxPower [dBm]

3-0 OutputPower rw 0x0f Pout=Pmax-(15-OutputPower) if PaSelect = 0 (RFO pin)

Pout=17-(15-OutputPower) if PaSelect = 1 (PA_BOOST pin)

RegPaRamp

(0x0A)

7-5 unused r - unused

4reserved rw 0x00 reserved

3-0 PaRamp(3:0) rw 0x09

Rise/Fall time of ramp up/down in FSK

0000  3.4 ms

0001  2 ms

0010  1 ms

0011  500 us

0100  250 us

0101  125 us

0110  100 us

0111  62 us

1000  50 us

1001  40 us

1010  31 us

1011  25 us

1100  20 us

1101  15 us

1110  12 us

1111  10 us

RegOcp

(0x0B

7-6 unused r 0x00 unused

5OcpOn rw 0x01

Enables overload current protection (OCP) for PA:

0  OCP disabled

1  OCP enabled

4-0 OcpTrim rw 0x0b

Trimming of OCP current:

Imax = 45+5*OcpTrim [mA] if OcpTrim <= 15 (120 mA) /

Imax = -30+10*OcpTrim [mA] if 15 < OcpTrim <= 27 (130 to

240 mA)

Imax = 240mA for higher settings

Default Imax = 100mA

Name

(Address) Bits Variable Name Mode Reset LoRaTM Description

fRF

F(XOSC) Frf⋅

219

------------------------------------

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RegLna

(0x0C)

7-5 LnaGain rwx 0x01

LNA gain setting:

000  not used

001  G1 = maximum gain

010  G2

011  G3

100  G4

101  G5

110  G6 = minimum gain

111  not used

4-3 LnaBoostLf rw 0x00

Low Frequency (RFI_LF) LNA current adjustment

00  Default LNA current

Other  Reserved

2reserved rw 0x00 reserved

1-0 LnaBoostHf rw 0x00

High Frequency (RFI_HF) LNA current adjustment

00  Default LNA current

11  Boost on, 150% LNA current

Lora page registers

RegFifoAddrPtr

(0x0D)

7-0 FifoAddrPtr rw 0x00 SPI interface address pointer in FIFO data buffer.

RegFifoTxBaseAd

(0x0E)

7-0 FifoTxBaseAddr rw 0x80 write base address in FIFO data buffer for TX modulator

RegFifoRxBaseAd

(0x0F)

7-0 FifoRxBaseAddr rw 0x00 read base address in FIFO data buffer for RX demodulator

RegFifoRxCurrent

Addr

(0x10)

7-0 FifoRxCurrentAddr r n/a Start address (in data buffer) of last packet received

RegIrqFlagsMask

(0x11)

7RxTimeoutMask rw 0x00 Timeout interrupt mask: setting this bit masks the corresponding

IRQ in RegIrqFlags

6RxDoneMask rw 0x00 Packet reception complete interrupt mask: setting this bit masks

the corresponding IRQ in RegIrqFlags

5PayloadCrcErrorMask rw 0x00 Payload CRC error interrupt mask: setting this bit masks the

corresponding IRQ in RegIrqFlags

4ValidHeaderMask rw 0x00 Valid header received in Rx mask: setting this bit masks the

corresponding IRQ in RegIrqFlags

3TxDoneMask rw 0x00 FIFO Payload transmission complete interrupt mask: setting this

bit masks the corresponding IRQ in RegIrqFlags

2CadDoneMask rw 0x00 CAD complete interrupt mask: setting this bit masks the

corresponding IRQ in RegIrqFlags

1FhssChangeChannelM

ask rw 0x00 FHSS change channel interrupt mask: setting this bit masks the

corresponding IRQ in RegIrqFlags

0CadDetectedMask rw 0x00 Cad Detected Interrupt Mask: setting this bit masks the

corresponding IRQ in RegIrqFlags

Name

(Address) Bits Variable Name Mode Reset LoRaTM Description

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RegIrqFlags

(0x12)

7RxTimeout rc 0x00 Timeout interrupt: writing a 1 clears the IRQ

6RxDone rc 0x00 Packet reception complete interrupt: writing a 1 clears the IRQ

5PayloadCrcError rc 0x00 Payload CRC error interrupt: writing a 1 clears the IRQ

4ValidHeader rc 0x00 Valid header received in Rx: writing a 1 clears the IRQ

3TxDone rc 0x00 FIFO Payload transmission complete interrupt: writing a 1 clears

the IRQ

2CadDone rc 0x00 CAD complete: write to clear: writing a 1 clears the IRQ

1FhssChangeChannel rc 0x00 FHSS change channel interrupt: writing a 1 clears the IRQ

0CadDetected rc 0x00 Valid Lora signal detected during CAD operation: writing a 1

clears the IRQ

RegRxNbBytes

(0x13)

7-0 FifoRxBytesNb r n/a Number of payload bytes of latest packet received

RegRxHeaderCnt

ValueMsb

(0x14)

7-0 ValidHeaderCntMsb(15:

8) rn/a

Number of valid headers received since last transition into Rx

mode, MSB(15:8). Header and packet counters are reseted in

Sleep mode.

RegRxHeaderCnt

ValueLsb

(0x15)

7-0 ValidHeaderCntLsb(7:0) r n/a

Number of valid headers received since last transition into Rx

mode, LSB(7:0). Header and packet counters are reseted in

Sleep mode.

RegRxPacketCntV

alueMsb

(0x16)

7-0 ValidPacketCntMsb(15:

8) rc n/a

Number of valid packets received since last transition into Rx

mode, MSB(15:8). Header and packet counters are reseted in

Sleep mode.

RegRxPacketCntV

alueLsb

(0x17)

7-0 ValidPacketCntLsb(7:0) r n/a

Number of valid packets received since last transition into Rx

mode, LSB(7:0). Header and packet counters are reseted in

Sleep mode.

RegModemStat

(0x18)

7-5 RxCodingRate r n/a Coding rate of last header received

ModemStatus

r ‘1’ Modem clear

3 r ‘0’ Header info valid

2 r ‘0’ RX on-going

1 r ‘0’ Signal synchronized

0 r ‘0’ Signal detected

RegPktSnrValue

(0x19) 7-0 PacketSnr rn/a

Estimation of SNR on last packet received.In two’s compliment

format mutiplied by 4.

Name

(Address) Bits Variable Name Mode Reset LoRaTM Description

SNR dB[] PacketSnr twos complement[]

-----------------------------------------------------------------------------------=

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RegPktRssiValue

(0x1A) 7-0 PacketRssi r n/a

RSSI of the latest packet received (dBm):

RSSI[dBm] = -157 + Rssi (using HF output port, SNR >= 0)

RSSI[dBm] = -164 + Rssi (using LF output port, SNR >= 0)

(see section 5.5.5 for details)

RegRssiValue

(0x1B) 7-0 Rssi r n/a

Current RSSI value (dBm)

RSSI[dBm] = -157 + Rssi (using HF output port)

RSSI[dBm] = -164 + Rssi (using LF output port)

(see section 5.5.5 for details)

RegHopChannel

(0x1C)

7PllTimeout r n/a PLL failed to lock while attempting a TX/RX/CAD operation

1  PLL did not lock

0  PLL did lock

6CrcOnPayload r n/a

CRC Information extracted from the received packet header

(Explicit header mode only)

0  Header indicates CRC off

1  Header indicates CRC on

5-0 FhssPresentChannel r n/a Current value of frequency hopping channel in use.

RegModemConfig

(0x1D)

7-4 Bw rw 0x07

Signal bandwidth:

0000  7.8 kHz

0001  10.4 kHz

0010  15.6 kHz

0011  20.8kHz

0100  31.25 kHz

0101  41.7 kHz

0110  62.5 kHz

0111  125 kHz

1000  250 kHz

1001  500 kHz

other values  reserved

In the lower band (169MHz), signal bandwidths 8&9 are not

supported)

3-1 CodingRate rw ‘001’

Error coding rate

001  4/5

010  4/6

011  4/7

100  4/8

All other values  reserved

In implicit header mode should be set on receiver to determine

expected coding rate. See 4.1.1.3

0ImplicitHeaderModeOn rw 0x0 0  Explicit Header mode

1  Implicit Header mode

Name

(Address) Bits Variable Name Mode Reset LoRaTM Description

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RegModemConfig

(0x1E)

7-4 SpreadingFactor rw 0x07

SF rate (expressed as a base-2 logarithm)

6  64 chips / symbol

7  128 chips / symbol

8  256 chips / symbol

9  512 chips / symbol

10  1024 chips / symbol

11  2048 chips / symbol

12  4096 chips / symbol

other values reserved.

3TxContinuousMode rw 0

0  normal mode, a single packet is sent

1  continuous mode, send multiple packets across the FIFO

(used for spectral analysis)

2RxPayloadCrcOn rw 0x00

Enable CRC generation and check on payload:

0 CRC disable

1 CRC enable

If CRC is needed, RxPayloadCrcOn should be set:

- in Implicit header mode: on Tx and Rx side

- in Explicit header mode: on the Tx side alone (recovered from

the header in Rx side)

1-0 SymbTimeout(9:8) rw 0x00 RX Time-Out MSB

RegSymbTimeoutL

(0x1F)

7-0 SymbTimeout(7:0) rw 0x64

RX Time-Out LSB

RX operation time-out value expressed as number of symbols:

RegPreambleMsb

(0x20) 7-0 PreambleLength(15:8) rw 0x0 Preamble length MSB, = PreambleLength + 4.25 Symbols

See 4.1.1 for more details.

RegPreambleLsb

(0x21) 7-0 PreambleLength(7:0) rw 0x8 Preamble Length LSB

RegPayloadLength

(0x22) 7-0 PayloadLength(7:0) rw 0x1

Payload length in bytes. The register needs to be set in implicit

header mode for the expected packet length. A 0 value is not

permitted

RegMaxPayloadLe

ngth

(0x23)

7-0 PayloadMaxLength(7:0) rw 0xff

Maximum payload length; if header payload length exceeds

value a header CRC error is generated. Allows filtering of packet

with a bad size.

RegHopPeriod

(0x24) 7-0 FreqHoppingPeriod(7:0) rw 0x0 Symbol periods between frequency hops. (0 = disabled). 1st hop

always happen after the 1st header symbol

RegFifoRxByteAdd

(0x25)

7-0 FifoRxByteAddrPtr r n/a Current value of RX databuffer pointer (address of last byte

written by Lora receiver)

Name

(Address) Bits Variable Name Mode Reset LoRaTM Description

TimeOut SymbTimeout Ts⋅=

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RegModemConfig

(0x26)

7-4 Unused r 0x00

LowDataRateOptimize rw 0x00 0  Disabled

1  Enabled; mandated for when the symbol length exceeds

16ms

2AgcAutoOn rw 0x00 0  LNA gain set by register LnaGain

1  LNA gain set by the internal AGC loop

1-0 Reserved rw 0x00 Reserved

(0x27) 7-0 PpmCorrection rw 0x00 Data rate offset value, used in conjunction with AFC

RegFeiMsb

(0x28)

7-4 Reserved r n/a Reserved

3-0 FreqError(19:16) r 0x0

Estimated frequency error from modem

MSB of RF Frequency Error

RegFeiMid

(0x29) 7-0 FreqError(15:8) r 0x0 Middle byte of RF Frequency Error

RegFeiLsb

(0x2A) 7-0 FreqError(7:0) r 0x0 LSB of RF Frequency Error

(0x2B) -Reserved r n/a Reserved

RegRssiWideband

(0x2C) 7-0 RssiWideband(7:0) r n/a Wideband RSSI measurement used to locally generate a

random number

(0x2D) - (0x30) -Reserved r n/a Reserved

RegDetectOptimiz

(0x31)

7-3 Reserved r 0xC0 Reserved

2-0 DetectionOptimize rw 0x03

LoRa Detection Optimize

0x03  SF7 to SF12

0x05  SF6

(0x32) -Reserved r n/a Reserved

RegInvertIQ

(0x33)

7 Reserved rw 0x0 Reserved

6InvertIQ rw 0x0

Invert the LoRa I and Q signals

0  normal mode

1  I and Q signals are inverted

5-0 Reserved rw 0x27 Reserved

(0x34) - (0x36) 7-0 Reserved r n/a Reserved

RegDetectionThre

shold

(0x37)

7-0 DetectionThreshold rw 0x0A

LoRa detection threshold

0x0A  SF7 to SF12

0x0C  SF6

(0x38) -Reserved r n/a Reserved

RegSyncWord

(0x39) 7-0 SyncWord rw 0x12 LoRa Sync Word

Value 0x34 is reserved for LoRaWAN networks

Name

(Address) Bits Variable Name Mode Reset LoRaTM Description

FError

FreqError 224

Fxtal

------------------------------------------BW kHz[]

500

------------------------

×=

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(0x3A) - (0x3F) -Reserved r n/a Reserved

Name

(Address) Bits Variable Name Mode Reset LoRaTM Description

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7. Application Information

7.1. Crystal Resonator Specification

Tab le 45 shows the crystal resonator specification for the crystal reference oscillator circuit of the SX1276/77/78/79. This

specification covers the full range of operation of the SX1276/77/78/79 and is employed in the reference design.

Table 45 Crystal Specification

Notes - the initial frequency tolerance, temperature stability and aging performance should be chosen in accordance with

the target operating temperature range and the receiver bandwidth selected.

- the loading capacitance should be applied externally, and adapted to the actual Cload specification of the XTAL.

7.2. Reset of the Chip

A power-on reset of the SX1276/77/78/79 is triggered at power up. Additionally, a manual reset can be issued by

controlling pin 7.

7.2.1. POR

If the application requires the disconnection of VDD from the SX1276/77/78/79, despite of the extremely low Sleep Mode

current, the user should wait for 10 ms from of the end of the POR cycle before commencing communications over the SPI

bus. Pin 7 (NRESET) should be left floating during the POR sequence.

Figure 42. POR Timing Diagram

Please note that any CLKOUT activity can also be used to detect that the chip is ready.

Symbol Description Conditions Min Typ Max Unit

FXOSC XTAL Frequency -32 -MHz

RS XTAL Serial Resistance -15 100 ohms

C0 XTAL Shunt Capacitance - 1 3 pF

CFOOT External Foot Capacitance On each pin XTA and XTB 10 15 22 pF

CLOAD Crystal Load Capacitance 6 - 12 pF

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7.2.2. Manual Reset

A manual reset of the SX1276/77/78/79 is possible even for applications in which VDD cannot be physically disconnected.

Pin 7 should be pulled low for a hundred microseconds, and then released. The user should then wait for 5 ms before using

the chip.

Figure 43. Manual Reset Timing Diagram

Note whilst pin 7 is driven low, an over current consumption of up to one milliampere can be seen on VDD.

7.3. Top Sequencer: Listen Mode Examples

In this scenario, the circuit spends most of the time in Idle mode, during which only the RC oscillator is on. Periodically the

receiver wakes up and looks for incoming signal. If a wanted signal is detected, the receiver is kept on and data are

analyzed. Otherwise, if there was no wanted signal for a defined period of time, the receiver is switched off until the next

receive period.

During Listen mode, the Radio stays most of the time in a Low Power mode, resulting in very low average power

consumption. The general timing diagram of this scenario is given in Figure 44.

Figure 44. Listen Mode: Principle

An interrupt request is generated on a packet reception. The user can then take appropriate action.

Depending on the application and environment, there are several ways to implement Listen mode:

Wake on a PreambleDetect interrupt

Wake on a SyncAddress interrupt

Wake on a PayloadReady interrupt

7.3.1. Wake on Preamble Interrupt

In one possible scenario, the sequencer polls for a Preamble detection. If a preamble signal is detected, the sequencer is

switched off and the circuit stays in Receive mode until the user switches modes. Otherwise, the receiver is switched off

until the next Rx period.

Listen mode : principle

Receive ReceiveIdle ( Sleep + RC ) Idle

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7.3.1.1. Timing Diagram

When no signal is received, the circuit wakes every Timer1 + Timer2 and switches to Receive mode for a time defined by

Timer2, as shown on the following diagram. If no Preamble is detected, it then switches back to Idle mode, i.e. Sleep mode

with RC oscillator on.

Figure 45. Listen Mode with No Preamble Received

If a Preamble signal is detected, the Sequencer is switched off. The PreambleDetect signal can be mapped to DIO4, in

order to request the user's attention. The user can then take appropriate action.

Figure 46. Listen Mode with Preamble Received

No received signal

Receive ReceiveIdle ( Sleep + RC ) Idle

Timer2

Timer1

Timer2

Timer1Timer1

Timer2

Received signal

Preamble ( As long as T1 + 2 * T2 ) Sync

Word Payload Crc

ReceiveIdle ( Sleep + RC )

Timer1

Preamble

Detect

Timer2

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7.3.1.2. Sequencer Configuration

The following graph shows Listen mode - Wake on PreambleDetect state machine:

Figure 47. Wake On PreambleDetect State Machine

This example configuration is achieved as follows:

Table 46 Listen Mode with PreambleDetect Condition Settings

TTimer2 defines the maximum duration the chip stays in Receive mode as long as no Preamble is detected. In order to

optimize power consumption, Timer2 must be set just long enough for Preamble detection.

TTimer1 + TTimer2 defines the cycling period, i.e. time between two Preamble polling starts. In order to optimize average

power consumption, Timer1 should be relatively long. However, increasing Timer1 also extends packet reception duration.

In order to insure packet detection and optimize the receiver's power consumption, the received packet Preamble should

be as long as TTimer1 + 2 x TTimer2.

An example of DIO configuration for this mode is described in the following table:

Table 47 Listen Mode with PreambleDetect Condition Recommended DIO Mapping

Variable Effect

IdleMode 1: Sleep mode

FromStart 00: To LowPowerSelection

LowPowerSelection 1: To Idle state

FromIdle 1: To Receive state on T1 interrupt

FromReceive 110: To Sequencer Off on PreambleDetect interrupt

DIO Value Description

001CrcOk

1 00 FifoLevel

300FifoEmpty

4 11 PreambleDetect – Note: MapPreambleDetect bit should be set.

State Machine

LowPower

Selection Idle

Receive

LowPowerSelection = 1

On T2

On T1

FromIdle = 1

On PreambleDetect

FromReceive = 110 Sequencer Off

IdleMode = 1 : Sleep

Start

Sequencer Off

Initial mode = Sleep or Standby

Start bit set

FromStart = 00

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7.3.2. Wake on SyncAddress Interrupt

In another possible scenario, the sequencer polls for a Preamble detection and then for a valid SyncAddress interrupt. If

events occur, the sequencer is switched off and the circuit stays in Receive mode until the user switches modes.

Otherwise, the receiver is switched off until the next Rx period.

7.3.2.1. Timing Diagram

Most of the sequencer running time is spent while no wanted signal is received. As shown by the timing diagram in

Figure 48, the circuit wakes periodically for a short time, defined by RxTimeout. The circuit is in a Low Power mode for the

rest of Timer1 + Timer2 (i.e. Timer1 + Timer2 - TrxTimeout)

Figure 48. Listen Mode with no SyncAddress Detected

If a preamble is detected before RxTimeout timer ends, the circuit stays in Receive mode and waits for a valid

SyncAddress detection. If none is detected by the end of Timer2, Receive mode is deactivated and the polling cycle

resumes, without any user intervention.

Figure 49. Listen Mode with Preamble Received and no SyncAddress

But if a valid Sync Word is detected, a SyncAddress interrupt is fired, the Sequencer is switched off and the circuit stays in

Receive mode as long as the user doesn't switch modes.

No wanted signal

Receive ReceiveIdle ( Sleep + RC )Idle Idle

Timer2

Timer1

Timer2

Timer1Timer1

RxTimeout RxTimeout

Unwanted Signal

Preamble ( Preamble + Sync = T2 ) Wrong

Word Payload Crc

Preamble

Detect

Receive ReceiveIdleIdle Idle

Timer2

Timer1

Timer2

Timer1Timer1

RxTimeout

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Figure 50. Listen Mode with Preamble Received & Valid SyncAddress

7.3.2.2. Sequencer Configuration

The following graph shows Listen mode - Wake on SyncAddress state machine:

Figure 51. Wake On SyncAddress State Machine

Wanted Signal

Preamble ( Preamble + Sync = T2 ) Sync

Word Payload Crc

Preamble

Detect

ReceiveIdle

Timer2

Timer1

Sync

Address

Fifo

Level

RxTimeout

State Machine

LowPower

Selection Idle

ReceiveRxTimeout

LowPowerSelection = 1

FromRxTimeout = 10

On RxTimeout

On T2

On T1

FromIdle = 1

On SyncAdress

FromReceive = 101 Sequencer Off

IdleMode = 1 : Sleep

Start

FromStart = 00

Sequencer Off

Initial mode = Sleep or Standby

Start bit set

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This example configuration is achieved as follows:

Table 48 Listen Mode with SyncAddress Condition Settings

TTimeoutRxPreamble should be set to just long enough to catch a preamble (depends on PreambleDetectSize and BitRate).

TTimer1 should be set to 64 µs (shortest possible duration).

TTimer2 is set so that TTimer1 + TTimer2 defines the time between two start of reception.

In order to insure packet detection and optimize the receiver power consumption, the received packet Preamble should be

defined so that TPreamble = TTimer2 - TSyncAddress with TSyncAddress = (SyncSize + 1)*8/BitRate.

An example of DIO configuration for this mode is described in the following table:

Table 49 Listen Mode with PreambleDetect Condition Recommended DIO Mapping

Variable Effect

IdleMode 1: Sleep mode

FromStart 00: To LowPowerSelection

LowPowerSelection 1: To Idle state

FromIdle 1: To Receive state on T1 interrupt

FromReceive 101: To Sequencer off on SyncAddress interrupt

FromRxTimeout 10: To LowPowerSelection

DIO Value Description

001CrcOk

1 00 FifoLevel

2 11 SyncAddress

300FifoEmpty

4 11 PreambleDetect – Note: MapPreambleDetect bit should be set.

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7.4. Top Sequencer: Beacon Mode

In this mode, a repetitive message is transmitted periodically. If the Payload being sent is always identical, and

PayloadLength is smaller than the FIFO size, the use of the BeaconOn bit in RegPacketConfig2 together with the

Sequencer permit to achieve periodic beacon without any user intervention.

7.4.1. Timing diagram

In this mode, the Radio is switched to Transmit mode every TTimer1 + TTimer2 and back to Idle mode after PacketSent, as

shown in the diagram below. The Sequencer insures minimal time is spent in Transmit mode, and therefore power

consumption is optimized.

Figure 52. Beacon Mode Timing Diagram

7.4.2. Sequencer Configuration

The Beacon mode state machine is presented in the following graph. It is noticeable that the sequencer enters an infinite

loop and can only be stopped by setting SequencerStop bit in RegSeqConfig1.

Figure 53. Beacon Mode State Machine

Beacon mode

Transmit TransmitIdle ( Sleep + RC )Idle Idle

Timer2

Timer1 Timer1Timer1

Timer2

Packet

Sent

Packet

Sent

State Machine

Transmit

On T1

FromIdle = 0

On PacketSent

FromTransmit = 0

LowPower

Selection Idle

LowPowerSelection = 1

IdleMode = 1 : Sleep

Start

FromStart = 00

Sequencer Off

Initial mode = Sleep or Standby

Start bit set

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This example is achieved by programming the Sequencer as follows:

Table 50 Beacon Mode Settings

TTimer1 + TTimer2 define the time between the start of two transmissions.

Variable Effect

IdleMode 1: Sleep mode

FromStart 00: To LowPowerSelection

LowPowerSelection 1: To Idle state

FromIdle 0: To Transmit state on T1 interrupt

FromTransmit 0: To LowPowerSelection on PacketSent interrupt

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7.5. Example CRC Calculation

The following routine(s) may be implemented to mimic the CRC calculation of the SX1276/77/78/79:

Figure 54. Example CRC Code

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7.6. Example Temperature Reading

The following routine(s) may be implemented to read the temperature and calibrate the sensor:

Figure 55. Example Temperature Reading

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Figure 56. Example Temperature Reading (continued)

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8. Packaging Information

8.1. Package Outline Drawing

The SX1276/77/78/79 is available in a 28-lead QFN package as shown in Figure 57.

Figure 57. Package Outline Drawing

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8.2. Recommended Land Pattern

Figure 58. Recommended Land Pattern

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8.3. Tape & Reel Information

Figure 59. Tape and Reel Information

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9. Revision History

Table 51 Revision History

Revision Date Comment

1 Sept 2013 First FINAL release

2Nov 2014

Miscellaneous typographical corrections

Correction of RxPayloadCrcOn description

Improve description in the RSSI and IQ calibration mechanism

Correction of ToA formulae

Inclusion of FEI and automatic frequency correction for LoRa

Corrected Rssi Formula in Lora mode

3 Nov 2014 Addition of part SX1279

4 March 2015

Clarified operation modes for Rx Single and Rx Continuous mode in LoRa

Added use cases for Rx Single and Rx Continuous mode in LoRa mode

Clarified used of LoRa RxPayloadCrcOn in Register Table

Added description of register RegSyncWord in LoRa register table

Changed Stand-By typo into Standby

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