Overview

This is a python interface to the Semtech SX1276/7/8/9 long range, low power transceiver family.

This project is forked from https://github.com/mayeranalytics/pySX127x

Hardware

The transceiver module is a SX1276 based Modtronix inAir9B. Pinout on a Raspberry 3 Model B

Proto board pin	RaspPi GPIO	Direction
inAir9B DIO0	GPIO 22	IN
inAir9B DIO1	GPIO 23	IN
inAir9B DIO2	GPIO 24	IN
inAir9B DIO3	GPIO 25	IN
inAir9b Reset	GPIO ?	OUT
LED	GPIO 18	OUT
Switch	GPIO 4	IN

Installation

Make sure SPI is activated on you RaspberryPi: SPI pySX127x requires these two python packages:

• RPi.GPIO for accessing the GPIOs, it should be already installed on a standard Raspian Linux image
• spidev for controlling SPI

In order to install spidev download the source code and run setup.py manually:

wget https://pypi.python.org/packages/source/s/spidev/spidev-3.1.tar.gz
tar xfvz  spidev-3.1.tar.gz
cd spidev-3.1
sudo python setup.py install

Class Reference

The interface to the SX127x LoRa modem is implemented in the class SX127x.LoRa.LoRa. The most important modem configuration parameters are:

Function	Description
set_mode	Change OpMode, use the constants.MODE class
set_freq	Set the frequency
set_bw	Set the bandwidth 7.8kHz ... 500kHz
set_coding_rate	Set the coding rate 4/5, 4/6, 4/7, 4/8
@todo

Most set_* functions have a mirror get_* function, but beware that the getter return types do not necessarily match the setter input types.

Register naming convention

The register addresses are defined in class SX127x.constants.REG and we use a specific naming convention which is best illustrated by a few examples:

Register	Modem	Semtech doc.	pySX127x
0x0E	LoRa	RegFifoTxBaseAddr	REG.LORA.FIFO_TX_BASE_ADDR
0x0E	FSK	RegRssiCOnfig	REG.FSK.RSSI_CONFIG
0x1D	LoRa	RegModemConfig1	REG.LORA.MODEM_CONFIG_1
etc.

Hardware

Hardware related definition and initialisation are located in SX127x.board_config.BOARD. If you use a SBC other than the Raspberry Pi you'll have to adapt the BOARD class.

Script references

Continuous receiver rx_cont.py

The SX127x is put in RXCONT mode and continuously waits for transmissions. Upon a successful read the payload and the irq flags are printed to screen.

usage: rx_cont.py [-h] [--ocp OCP] [--sf SF] [--freq FREQ] [--bw BW]
                  [--cr CODING_RATE] [--preamble PREAMBLE]

Continous LoRa receiver

optional arguments:
  -h, --help            show this help message and exit
  --ocp OCP, -c OCP     Over current protection in mA (45 .. 240 mA)
  --sf SF, -s SF        Spreading factor (6...12). Default is 7.
  --freq FREQ, -f FREQ  Frequency
  --bw BW, -b BW        Bandwidth (one of BW7_8 BW10_4 BW15_6 BW20_8 BW31_25
                        BW41_7 BW62_5 BW125 BW250 BW500). Default is BW125.
  --cr CODING_RATE, -r CODING_RATE
                        Coding rate (one of CR4_5 CR4_6 CR4_7 CR4_8). Default
                        is CR4_5.
  --preamble PREAMBLE, -p PREAMBLE
                        Preamble length. Default is 8.

Simple LoRa beacon tx_beacon.py

A small payload is transmitted in regular intervals.

usage: tx_beacon.py [-h] [--ocp OCP] [--sf SF] [--freq FREQ] [--bw BW]
                    [--cr CODING_RATE] [--preamble PREAMBLE] [--single]
                    [--wait WAIT]

A simple LoRa beacon

optional arguments:
  -h, --help            show this help message and exit
  --ocp OCP, -c OCP     Over current protection in mA (45 .. 240 mA)
  --sf SF, -s SF        Spreading factor (6...12). Default is 7.
  --freq FREQ, -f FREQ  Frequency
  --bw BW, -b BW        Bandwidth (one of BW7_8 BW10_4 BW15_6 BW20_8 BW31_25
                        BW41_7 BW62_5 BW125 BW250 BW500). Default is BW125.
  --cr CODING_RATE, -r CODING_RATE
                        Coding rate (one of CR4_5 CR4_6 CR4_7 CR4_8). Default
                        is CR4_5.
  --preamble PREAMBLE, -p PREAMBLE
                        Preamble length. Default is 8.
  --single, -S          Single transmission
  --wait WAIT, -w WAIT  Waiting time between transmissions (default is 0s)