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u-lora

This is a port of raspi-lora (https://pypi.org/project/raspi-lora/) for micropython. I have tested on raspberry pi pico, esp8266, and esp32. It allows your microcontroller to use an RFM95 radio to communicate.

Wiring

The pinout for the RFM95 module can be found on page 10 of the documentation (https://cdn.sparkfun.com/assets/learn_tutorials/8/0/4/RFM95_96_97_98W.pdf). The pin numbers below are for the RFM95 - look at your microcontroller docs for the pins to connect to them.

Power (the RFM95 module requires 3.3V from your microcontroller):

  • connect 3.3V to pin 13
  • connect GND to pin 1, 8, or 10 on the RFM95 module

For SPI communication:

  • MISO to pin 2 (MISO)
  • MOSI to pin 3 (MOSI)
  • SCK to pin 4 (SCK)
  • CS to pin 5 (NSS)

Other pins:

  • Use a GPIO output to pin 6 (RESET) for resetting the RFM95
  • Use a GPIO input to pin 14 (D) to trigger that a message has been received

Configuration

INITIALIZATION

LoRa(spi_channel, interrupt, this_address, cs_pin, reset_pin=None, freq=868, tx_power=14,
    modem_config=ModemConfig.Bw125Cr45Sf128, acks=False, crypto=None)

spi_channel SPI channel, check SPIConfig for preconfigured names, e.g. SPIConfig.rp2_0 for RPi pico channel 0
interrupt GPIO pin to use for the interrupt
this_address The address number (0-254) your device will use when sending and receiving packets.
cs_pin chip select pin from microcontroller
reset_pin : the GPIO used to reset the RFM9x if connected
freq Frequency used by your LoRa radio. Defaults to 868Mhz
tx_power Transmission power level from 5 to 23. Keep this as low as possible. Defaults to 14
modem_config Modem configuration. See RadioHead docs. Default to Bw125Cr45Sf128.
receive_all Receive messages regardless of the destination address
acks If True, send an acknowledgment packet when a message is received and wait for an acknowledgment when transmitting a message. This is equivalent to using RadioHead's RHReliableDatagram
crypto An instance of PyCryptodome Cipher.AES (not tested) - should be able to use ucrypto

SPICONFIG

Preconfigured SPI bus pins for tested devices, just add into the class for other devices

class SPIConfig():
    # spi pin defs for various boards (channel, sck, mosi, miso)
    rp2_0 = (0, 6, 7, 4)
    rp2_1 = (1, 10, 11, 8)
    esp8286_1 = (1, 14, 13, 12)
    esp32_1 = (1, 14, 13, 12)
    esp32_2 = (2, 18, 23, 19)

ModemConfig

Preconfigured modem settings taken from Radiohead docs, I will try and add the ability to fine tune these in future.

    Bw125Cr45Sf128 = (0x72, 0x74, 0x04) #< Bw = 125 kHz, Cr = 4/5, Sf = 128chips/symbol, CRC on. Default medium range
    Bw500Cr45Sf128 = (0x92, 0x74, 0x04) #< Bw = 500 kHz, Cr = 4/5, Sf = 128chips/symbol, CRC on. Fast+short range
    Bw31_25Cr48Sf512 = (0x48, 0x94, 0x04) #< Bw = 31.25 kHz, Cr = 4/8, Sf = 512chips/symbol, CRC on. Slow+long range
    Bw125Cr48Sf4096 = (0x78, 0xc4, 0x0c) #/< Bw = 125 kHz, Cr = 4/8, Sf = 4096chips/symbol, low data rate, CRC on. Slow+long range
    Bw125Cr45Sf2048 = (0x72, 0xb4, 0x04) #< Bw = 125 kHz, Cr = 4/5, Sf = 2048chips/symbol, CRC on. Slow+long range

Examples

There are two examples to test sending and receiving data in the examples folder

Server mode:

Copy the file server.py to your main.py and copy it across together with the library ulora.py to your microcontroller

from time import sleep
from ulora import LoRa, ModemConfig, SPIConfig

# This is our callback function that runs when a message is received
def on_recv(payload):
    print("From:", payload.header_from)
    print("Received:", payload.message)
    print("RSSI: {}; SNR: {}".format(payload.rssi, payload.snr))

# Lora Parameters
RFM95_RST = 27
RFM95_SPIBUS = SPIConfig.rp2_0
RFM95_CS = 5
RFM95_INT = 28
RF95_FREQ = 868.0
RF95_POW = 20
CLIENT_ADDRESS = 1
SERVER_ADDRESS = 2

# initialise radio
lora = LoRa(RFM95_SPIBUS, RFM95_INT, SERVER_ADDRESS, RFM95_CS, 
            reset_pin=RFM95_RST, freq=RF95_FREQ, tx_power=RF95_POW, acks=True)

# set callback
lora.on_recv = on_recv

# set to listen continuously
lora.set_mode_rx()

# loop and wait for data
while True:
    sleep(0.1)

Client mode:

Copy the file server.py to your main.py and copy it across together with the library ulora.py to your microcontroller

from time import sleep
from ulora import LoRa, ModemConfig, SPIConfig

# Lora Parameters
RFM95_RST = 27
RFM95_SPIBUS = SPIConfig.rp2_0
RFM95_CS = 5
RFM95_INT = 28
RF95_FREQ = 868.0
RF95_POW = 20
CLIENT_ADDRESS = 1
SERVER_ADDRESS = 2

# initialise radio
lora = LoRa(RFM95_SPIBUS, RFM95_INT, CLIENT_ADDRESS, RFM95_CS,
            reset_pin=RFM95_RST, freq=RF95_FREQ, tx_power=RF95_POW, acks=True)


# loop and send data
while True:
    lora.send_to_wait("This is a test message", SERVER_ADDRESS)
    print("sent")
    sleep(10)