Transmission

#include <SoftwareSerial.h>
#include <TinyGPS++.h>

// RX is -1 because we are only transmitting, TX is 8
SoftwareSerial radio(-1, 8);
// RX is 4 (GPS TX), TX is 3 (Not used)
SoftwareSerial gpsSerial(4, 3);
TinyGPSPlus gps;

bool running = true;

void setup() {
  Serial.begin(9600);
  radio.begin(9600);
  gpsSerial.begin(9600);
  Serial.println("TX ready. Press Enter in Serial Monitor to stop.");
}

void loop() {
  // Toggle logic for stopping/starting [cite: 7]
  if (Serial.available() > 0) {
    while (Serial.available() > 0) Serial.read();
    running = !running;
    Serial.println(running ? "--- Resuming ---" : "--- Paused ---");
  }

  // Feed GPS data to the parser
  while (gpsSerial.available() > 0) {
    gps.encode(gpsSerial.read());
  }

  // Only send data if running and we have a valid GPS lock
  if (running && gps.location.isUpdated()) {
    float lat = gps.location.lat();
    float lon = gps.location.lng();
    float alt = gps.altitude.meters();

    // Transmit raw bytes of GPS data [cite: 10]
    radio.write((uint8_t*)&lat, sizeof(lat));
    radio.write((uint8_t*)&lon, sizeof(lon));
    radio.write((uint8_t*)&alt, sizeof(alt));

    // Local debug print [cite: 11]
    Serial.print("Sent GPS -> Lat: ");
    Serial.print(lat, 6);
    Serial.print(" Lon: ");
    Serial.print(lon, 6);
    Serial.print(" Alt: ");
    Serial.println(alt);

    delay(1000);
  }
}