sounds.ino

// define variables
#define mp3RxPin 2
#define mp3TxPin 3
int volume = 255;
int mp3Byte = 0;
SoftwareSerial mp3Trigger = SoftwareSerial(mp3RxPin, mp3TxPin);
mp3Trigger.begin(38400);

// set volume
byte volbyte = map((volume-255), 0, 1023, 0, 255);
mp3Trigger.write('v');
mp3Trigger.write(volbyte);

//play some sounds
mp3Trigger.write('t');
mp3Trigger.write(1);

// stop a sound
mp3Trigger.write('O');