ESP32 Forum

Posted: **Mon Feb 01, 2021 1:07 am**

Hello everyone,
I have recently been exploring LoRa communication system and, inspired by the Meshtastic project to which I contributed in the early days, I decided to create a very basic two-way radio using a commercial LoRa module based on the ESP32.
Leveraging the two cores of the ESP32, I separated the logic into two threads, one responsible for sending messages and another for receiving. The TX thread also takes care of displaying the user interface via WiFi.

Now, going to the debug part, messages are correctly sent, I can see their spectral trace using a SDR dongle at 433MHz. However, somehow the receiving logic doesn't work. The RX thread is correctly working, there are no errors. I tried to replace with callbacks without success.

What can I do to find out the cause?

Here's the project files: https://github.com/grcasanova/Talker

Thank you

Here is the RX task code

Code: Select all

[Codebox=c file=Untitled.c]  
  while(true) {
    // try to parse packet
    int packetSize = LoRa.parsePacket();
    if (packetSize) {
      // received a packet
      Serial.print("Received packet");

      // read packet header bytes:
      int recipient = LoRa.read();          // recipient address
      byte sender = LoRa.read();            // sender address
      byte incomingMsgId = LoRa.read();     // incoming msg ID
      byte incomingLength = LoRa.read();    // incoming msg length

      String incoming = "";

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

      if (incomingLength != incoming.length()) { // check length for error
        Serial.println("error: message length does not match length");
        continue;  // skip rest of the cycle
      }

      // if the recipient isn't this device or broadcast,
      if (recipient != FROM_ADDR && recipient != ALL) {
        Serial.println("This message is not for me.");
        continue;  // skip rest of the cycle
      }

      // Save msg
      String temp = "<li class='you'>"+incoming+"</li>";
      appendFile(SPIFFS, FILENAME, temp.c_str());

      // if message is for this device, or broadcast, print details:
      Serial.println("Message: " + incoming);
      Serial.println("RSSI: " + String(LoRa.packetRssi()));
      Serial.println("SNR: " + String(LoRa.packetSnr()));
      Serial.println();

      screen.clear();
      screen.setTextAlignment(TEXT_ALIGN_LEFT);
      screen.setFont(ArialMT_Plain_10);
      screen.drawString(0, 0, "Received Message:");
      screen.drawString(0, 15, incoming);
      screen.display();
    }
    
    vTaskDelay(10);
  }
}[/Codebox]

Posted: **Mon Feb 01, 2021 7:21 am**

After quick pick on your code i have question, because i might miss it, where is LoRa switching to RX with lora.setRX(n) or lora.receive() which internally calls setRX()?
https://github.com/StuartsProjects/SX12 ... 7XLT.h#L57

Also you have to remember that you cant RX and TX at the same time, so you may miss some packets sometimes. In addition you have to call stRX() always after transmitting.

Posted: **Mon Feb 01, 2021 10:39 am**

I just followed Arduino LoRa library duplex example, where they don't use any switching between transmission and reception of data frames. Unless the "onReceive" callback already sets the radio in the receiving mode.

Regarding loss of packets, that's inherently connected to LoRa being half duplex, I haven't seen any special solution rather than basic buffering implemented in other projects like Meshtastic.

Code: [Select all] [Expand/Collapse]

#include <SPI.h>              // include libraries
#include <LoRa.h>
 
const int csPin = 7;          // LoRa radio chip select
const int resetPin = 6;       // LoRa radio reset
const int irqPin = 1;         // change for your board; must be a hardware interrupt pin
 
String outgoing;              // outgoing message
 
byte msgCount = 0;            // count of outgoing messages
byte localAddress = 0xBB;     // address of this device
byte destination = 0xFF;      // destination to send to
long lastSendTime = 0;        // last send time
int interval = 2000;          // interval between sends
 
void setup() {
  Serial.begin(9600);                   // initialize serial
  while (!Serial);
 
  Serial.println("LoRa Duplex");
 
  // override the default CS, reset, and IRQ pins (optional)
  LoRa.setPins(csPin, resetPin, irqPin);// set CS, reset, IRQ pin
 
  if (!LoRa.begin(915E6)) {             // initialize ratio at 915 MHz
    Serial.println("LoRa init failed. Check your connections.");
    while (true);                       // if failed, do nothing
  }
 
  Serial.println("LoRa init succeeded.");
}
 
void loop() {
  if (millis() - lastSendTime > interval) {
    String message = "HeLoRa World!";   // send a message
    sendMessage(message);
    Serial.println("Sending " + message);
    lastSendTime = millis();            // timestamp the message
    interval = random(2000) + 1000;    // 2-3 seconds
  }
 
  // parse for a packet, and call onReceive with the result:
  onReceive(LoRa.parsePacket());
}
 
void sendMessage(String outgoing) {
  LoRa.beginPacket();                   // start packet
  LoRa.write(destination);              // add destination address
  LoRa.write(localAddress);             // add sender address
  LoRa.write(msgCount);                 // add message ID
  LoRa.write(outgoing.length());        // add payload length
  LoRa.print(outgoing);                 // add payload
  LoRa.endPacket();                     // finish packet and send it
  msgCount++;                           // increment message ID
}
 
void onReceive(int packetSize) {
  if (packetSize == 0) return;          // if there's no packet, return
 
  // read packet header bytes:
  int recipient = LoRa.read();          // recipient address
  byte sender = LoRa.read();            // sender address
  byte incomingMsgId = LoRa.read();     // incoming msg ID
  byte incomingLength = LoRa.read();    // incoming msg length
 
  String incoming = "";
 
  while (LoRa.available()) {
    incoming += (char)LoRa.read();
  }
 
  if (incomingLength != incoming.length()) {   // check length for error
    Serial.println("error: message length does not match length");
    return;                             // skip rest of function
  }
 
  // if the recipient isn't this device or broadcast,
  if (recipient != localAddress && recipient != 0xFF) {
    Serial.println("This message is not for me.");
    return;                             // skip rest of function
  }
 
  // if message is for this device, or broadcast, print details:
  Serial.println("Received from: 0x" + String(sender, HEX));
  Serial.println("Sent to: 0x" + String(recipient, HEX));
  Serial.println("Message ID: " + String(incomingMsgId));
  Serial.println("Message length: " + String(incomingLength));
  Serial.println("Message: " + incoming);
  Serial.println("RSSI: " + String(LoRa.packetRssi()));
  Serial.println("Snr: " + String(LoRa.packetSnr()));
  Serial.println();
}

Posted: **Thu Feb 04, 2021 1:21 pm**

Sorry, my bad. I assumed you are using different library, and i dont know that one, so i cant help.

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