#define TX_PIN D6  // Connect to module's RX
#define RX_PIN D7  // Connect to module's TX

// Configuration
const int trackDuration = 1000;  // Play duration for each track (ms)

void setup() {
  Serial1.begin(9600, SERIAL_8N1, RX_PIN, TX_PIN); // Initialize UART
  randomSeed(analogRead(A0)); // Seed random generator
  setVolume(0x1E); // Set medium volume (0x00-0x1E)
}

void loop() {
  // Randomly select track (1=01.mp3, 2=02.mp3, 3=03.mp3)
  byte track = random(1, 4); 
  
  // Play selected track
  playTrack(track);
  
  // Wait for track to play
  delay(trackDuration); 
}

/**
 * Plays specified audio track
 * @param trackNum - Track number (1-3)
 */
void playTrack(unsigned char trackNum) {
  // Command format: [Header, Command, Len, Param1, TrackNum, Checksum]
  unsigned char cmd[6] = {0xAA, 0x07, 0x02, 0x00, trackNum, trackNum + 0xB3};
  Serial1.write(cmd, 6);
}

/**
 * Sets playback volume
 * @param vol - Volume level (0x00=mute, 0x1E=max)
 */
void setVolume(unsigned char vol) {
  unsigned char cmd[5] = {0xAA, 0x13, 0x01, vol, vol + 0xBE};
  Serial1.write(cmd, 5);
}