   Serial.println("Timeout!");
   onTimeout();
 
-  attachInterrupt(digitalPinToInterrupt(INT_PIN), trellisIsr, LOW);
+  attachInterrupt(digitalPinToInterrupt(TRELLIS_INT_PIN), trellisIsr, LOW);
   LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF); 
 
   if (state == TIMEOUT_WAIT) {

}

void initializeSwitchLed() {
  pinMode(GREEN_LED_PIN, OUTPUT);
  pinMode(BLUE_LED_PIN, OUTPUT);
  digitalWrite(GREEN_LED_PIN, HIGH);
  digitalWrite(BLUE_LED_PIN, HIGH);
}

void initializeAmplifier() {

     on key press play a music file from the micro SD card from a specific folder and blink the respective key (/)
     on pressing the same key or when playback stops jump to the next file in the folder, until all music is played (/)
     read the rotary decoder to change the volume, the maximum volume can be configured (/)
     press the rotary decoder to pause/resume/stop/sleep (/)
     detect when a headphone is plugged in and mute the amplifier for the internal speakers (/)
     switch the music box off automatically after an idle period

