LoRa Duplex B

Updated on 4 September 2021
dev board Arduino UNO
features lora duplex SPI
This tutorial is more than 1 year old. If the steps below do not work, then please check the latest versions and the documentations of the individual tools used.

Before starting

Dependancies

Ensure the following dependancies are downloaded and available:

Code

Download code lora-duplex-b.ino
#include <SPI.h>
#include <LoRa.h>

const int csPin = 7;
const int resetPin = 6;
const int irqPin = 1;

byte localAddress = 0xBB;
byte destinationAddress = 0xAA;
long lastSendTime = 0;
int interval = 2000;
int count = 0;

void setup() {
  Serial.begin(9600);
  Serial.println("Start LoRa duplex");
  Serial.print("Local address: ");
  Serial.println(String(localAddress, HEX));
  Serial.print("Destination address: ");
  Serial.print(String(destinationAddress, HEX));

  LoRa.setPins(csPin, resetPin, irqPin);

  if (!LoRa.begin(433E6)) {
    Serial.println("LoRa init failed. Check your connections.");
    while (true) {}
  }
}

void loop() {
  if (millis() - lastSendTime > interval) {
    String sensorData = String(count++);
    sendMessage(sensorData);

    Serial.print("Sending data " + sensorData);
    Serial.print(" from source 0x" + String(localAddress, HEX));
    Serial.println(" to destination 0x" + String(destinationAddress, HEX));

    lastSendTime = millis();
    interval = random(2000) + 1000;
  }

  receiveMessage(LoRa.parsePacket());
}

void sendMessage(String outgoing) {
  LoRa.beginPacket();
  LoRa.write(destinationAddress);
  LoRa.write(localAddress);
  LoRa.write(outgoing.length());
  LoRa.print(outgoing);
  LoRa.endPacket();
}

void receiveMessage(int packetSize) {
  if (packetSize == 0) return;

  int recipient = LoRa.read();
  byte sender = LoRa.read();
  byte incomingLength = LoRa.read();

  String incoming = "";

  while (LoRa.available()) {
    incoming += (char)LoRa.read();
  }

  if (incomingLength != incoming.length()) {
    Serial.println("Error: Message length does not match length");
    return;
  }

  if (recipient != localAddress) {
    Serial.println("Error: Recipient address does not match local address");
    return;
  }

  Serial.print("Received data " + incoming);
  Serial.print(" from 0x" + String(sender, HEX));
  Serial.println(" to 0x" + String(recipient, HEX));
}

Makefile

BOARD?=arduino:avr:uno
PORT?=/dev/cu.usbmodem14*

.PHONY: default lint all flash clean

default: lint all flash clean

lint:
	cpplint --extensions=ino --filter=-legal/copyright,-readability/casting,-runtime/int,-whitespace/line_length *.ino

all:
	arduino-cli compile --fqbn $(BOARD) ./

flash:
	arduino-cli upload -p $(PORT) --fqbn $(BOARD)

clean:
	rm -r build

Prototype

A photo of the actual setup.

LoRa Duplex B prototype

Schematic

Wire up the hardware accordingly

LoRa Duplex B schematic

Serial console

Serial output from the firmware.

LoRa Duplex B serial console

Description

Send and receive at the same time from another node! Use this code with duplex a.

byte localAddress = 0xFF;
byte destination = 0xBB;

References

Watch