loraPython

Python wrapper for a LoRa Raspberry Pi HAT.

It was tested with RFM95W LoRa module. Therefore it should work with following modules:

RFMW95W
SX1278
SX1276

Additional information on how to use the driver can be found on my blog.

API Documentation

The Python wrapper for a LoRa module offers three functions

init()
recv()
send()

init(mode, frequency, spread_factor)

Initializes LoRa module. Has to be invoked every time when the mode (transmitter/receiver) is being changed.

Takes 3 arguments:

mode (0 for transmitter, 1 for receiver),
frequency expressed in Hertz (make sure the LoRa module is compatible with selected frequency),
spread_factor Lora spread factor, available are 7, 8, 9, 10, 11 or 12.

Currently only bandwidth 125kHz and coding rate 4/5 are supported.

Returns 0 on success.

recv()

Returns a tuplet with 6 elements:

buffer (bytes),
number of received bytes,
PRRSI last packet RSSI (received signal strength indicator) [dBm]
RRSI current RSSI [dBm]
SNR signal noise ratio
error code (0, no error, != 0, otherwise)

If no data was received the second element of the tuplet is set to 0.

send(data)

Takes 1 parameter:

data byte array to be send.

Connection

The module has to be connected to the Raspberry Pi according to the table below

RFM95W pin	Raspberry Pi pin	Description
3.3V	3V3, pin 1	3V3 power supply
GND	GND, pin 6	power ground
MISO	GPIO 9 (MISO), pin 21	SPI Master Input Slave Output
MOSI	GPIO 10 (MOSI), pin 19	SPI Master Output Slave Input
SCK	GPIO 11 (SCLK), pin 23	SPI clock
NSS	GPIO 25, pin 22	SPI chip select
RESET	GPIO 17, pin 11	LoRa module reset
DIO0	GPIO 4 (GPCLK0), pin 7	LoRa status line

Compilation

Before compiling make sure the proper version in Makefile was selected. This can be configured through PYTHONVER variable.

Additionally wiringpi library is used. Install it before compilation with

sudo apt install wiringpi

For the library and example application

make all

For library only

make lib

Examples

Before running the examples make sure that SPI interface is enabled in Raspberry Pi. For this use command

sudo raspi-config

Navigate through the menu, enable SPI and restart RPi.

Receiver:

Configuration fo a simple receiver at 868MHz freqency.

import loralib
loralib.init(1, 868000000, 7)
data=loralib.recv();
data
>>> (b'hello', 5, -25, -94, 9, 0)

Receiver in a loop

Configuration of a receiver in a loop.

import loralib
import time

loralib.init(1, 868000000, 7)

for i in range(0,10000000):
  msg=loralib.recv()
  print("%06d, frame=" % i, end='')
  print(msg)
  time.sleep(1)

Configuration of a receiver in a loop with high frequency check and verification of message size and CRC.

import loralib
import time

loralib.init(1, 868000000, 7)

for i in range(0,10000000):
  msg=loralib.recv()
  if msg[5] == 0 and msg[1] > 0:
    print(msg)
  time.sleep(0.001)

Transmitter:

Transmitter sending a string "hello".

import loralib                                                          
loralib.init(0, 868000000, 7)                                           
loralib.send(b'hello');

Rashid-S/LoRa-RaspberryPi