microReticulumTbeam/exercises/01_lora_ascii_pingpong/src/main.cpp

// 20260212 ChatGPT
// $Id$
// $HeadURL$

#include <Arduino.h>
#include <SPI.h>
#include <RadioLib.h>

// --- Compile-time label ---
#ifndef NODE_LABEL
#define NODE_LABEL "?"
#endif

// --- Pins injected via platformio.ini build_flags ---
#ifndef LORA_CS
#error "LORA_CS not defined"
#endif
#ifndef LORA_DIO1
#error "LORA_DIO1 not defined"
#endif
#ifndef LORA_RESET
#error "LORA_RESET not defined"
#endif
#ifndef LORA_BUSY
#error "LORA_BUSY not defined"
#endif

// SX1262 on T-Beam Supreme (tbeam-s3-core pinout)
SX1262 radio = new Module(LORA_CS, LORA_DIO1, LORA_RESET, LORA_BUSY);

static volatile bool g_rx_flag = false;


static void onDio1Rise() {
  g_rx_flag = true;
}

static void print_config() {
  Serial.printf("Node=%s\n", NODE_LABEL);
  Serial.printf("Pins: CS=%d DIO1=%d RST=%d BUSY=%d SCK=%d MISO=%d MOSI=%d\r\n",
                (int)LORA_CS, (int)LORA_DIO1, (int)LORA_RESET, (int)LORA_BUSY,
                (int)LORA_SCK, (int)LORA_MISO, (int)LORA_MOSI);
  Serial.printf("LoRa: freq=915.0 BW=125 SF=7 CR=5 txp=14\r\n");
}

void setup() {
  Serial.begin(115200);
  delay(250);
  Serial.println();
  Serial.println("Exercise 01: LoRa ASCII ping-pong (serial only)");

  // Ensure SPI pins match the variant
  SPI.begin(LORA_SCK, LORA_MISO, LORA_MOSI, LORA_CS);

  int state = radio.begin(915.0 /* MHz */, 125.0 /* kHz */, 7 /* SF */, 5 /* CR */, 0x12 /* sync */, 14 /* dBm */);
  if (state != RADIOLIB_ERR_NONE) {
    Serial.printf("ERROR: radio.begin failed, code=%d\r\n", state);
    while (true) delay(1000);
  }

  // Match Meshtastic-like wiring assumptions for SX1262 modules:
  // - DIO2 used as RF switch
  // - TCXO at 1.8V
  //OLD radio.setDio2AsRfSwitch(true);
  //OLD radio.setTcxoVoltage((float)LORA_TCXO_VOLTAGE);
  // below is replacement for above 2 lines:

  //maybe_setDio2AsRfSwitch(radio, true);
  //maybe_setTcxoVoltage(radio, (float)LORA_TCXO_VOLTAGE);

  // end of replacement
  
  // Set up RX interrupt
  radio.setDio1Action(onDio1Rise);

  // Start receiving
  state = radio.startReceive();
  if (state != RADIOLIB_ERR_NONE) {
    Serial.printf("ERROR: startReceive failed, code=%d\r\n", state);
    while (true) delay(1000);
  }

  print_config();
}

void loop() {
  // Periodic TX (with a label-based offset to reduce collisions)
  static uint32_t next_tx_ms = 0;
  static uint32_t iter = 0;
  uint32_t now = millis();

  if (next_tx_ms == 0) {
    // Offset A and B so they don't always collide
    uint32_t offset = (NODE_LABEL[0] == 'A') ? 500 : 1500;
    next_tx_ms = now + offset;
  }

  if ((int32_t)(now - next_tx_ms) >= 0) {
    next_tx_ms = now + 2000; // 2 seconds for this smoke test

    // String msg = String("I am ") + NODE_LABEL + " iter=" + String(iter++);
    String msg = String(" ") + NODE_LABEL + " sends greetings. iter=" + String(iter++);
    Serial.printf("TX: %s\r\n", msg.c_str());

    //int tx = radio.transmit(msg);
    //if (tx != RADIOLIB_ERR_NONE) {
    //  Serial.printf("TX ERROR code=%d\r\n", tx);
    // }

    // After transmit, resume RX
    //radio.startReceive();
    // DIO1 triggers on TX-done as well as RX-done.
    // If left armed, TX completion looks like RX.
    g_rx_flag = false;
    radio.clearDio1Action();
    
    int tx = radio.transmit(msg);
    if (tx != RADIOLIB_ERR_NONE) {
      Serial.printf("TX ERROR code=%d\r\n", tx);
    }
    
    // Re-arm RX interrupt and resume RX
    g_rx_flag = false;
    radio.setDio1Action(onDio1Rise);
    radio.startReceive();

  }

  // RX handling
  if (g_rx_flag) {
    g_rx_flag = false;

    String rx;
    int state = radio.readData(rx);
    if (state == RADIOLIB_ERR_NONE) {
      Serial.printf("RX: %s | RSSI=%.1f SNR=%.1f\r\n",
                    rx.c_str(), radio.getRSSI(), radio.getSNR());
    } else {
      Serial.printf("RX ERROR code=%d\r\n", state);
    }

    // Keep receiving
    radio.startReceive();
  }

  delay(5);
}