Millis timer question

Question

Trying to figure out how to do this in millis. So right now the code works just fine, plays mp3_play(2) while a push button is closed then plays mp3_play(1) when its open. Lets say I want mp3_play(2) to play while the push button closed but after 4 seconds if the button is still closed another audio file will be triggered to play. Cant figure that one out.

thanks Jason

void fire(){

  int reading = digitalRead(buttonPin);
 
  if (reading != lastButtonState) {
    // reset the debouncing timer
    lastDebounceTime = millis();
  }
 
  if ((millis() - lastDebounceTime) > debounceDelay) {

    if (reading != buttonState) {
      buttonState = reading;
 
      if (buttonState == HIGH) {
        mp3_play (1); //power down sound 
      }
      
      if (buttonState == LOW) {  
        mp3_play (2);  // fire sound
      }
      
    }
  }
  lastButtonState = reading;
}

Answer 1

You have to keep track of time once a button is pressed (LOW). So buttonLowTime is initialized every time you press the button. In the if logic, you first check if the buttonstate is LOW and if the said time has been passed.

But you also mentioned you want to play the audio once. So you need to keep track if you already played the audio. So, a flag, timeoutAudioPlayed has been created to keep track of that. So, now, the 3rd audio will only play if:

1. The button is pressed
2. and is pressed for more than said time (BUTTON_LOW_TIME_MAX)
3. and if the audio hasn't been played.

void fire()
{
  static int buttonLowTime = 0; <-------------------
  static bool timeoutAudioPlayed = true; <---------
  
  int reading = digitalRead(buttonPin);
 
  if (reading != lastButtonState) 
  {
    // reset the debouncing timer
    lastDebounceTime = millis();
  }
 
  if ((millis() - lastDebounceTime) > debounceDelay) 
  {
    if (reading != buttonState) 
    {
      buttonState = reading;
 

      if (buttonState == HIGH) 
      {
        mp3_play (1); //power down sound 
      }
  
      if (buttonState == LOW) 
      {  
        mp3_play (2);  // fire sound
        buttonLowTime = millis(); <-----------
        timeoutAudioPlayed = false; <---------
      }
    }
  }

  // The logic for timeout audio <------------
  if((buttonState == LOW) && (millis() - buttonLowTime) > BUTTON_LOW_TIME_MAX && timeoutAudioPlayed == false)
  {
    mp3_play (3);
    timeoutAudioPlayed = true;
  }

  lastButtonState = reading;
}