Interactive BPM tracker using key taps, averaging over N taps for smoother BPM detection in Processing

bpm.pde

float bpm = 120;
float minute = 60000;
float interval = minute / bpm;
int time;
int beats = 0;

// Variables for BPM calculation based on key taps
int lastTapTime = 0;
int tapInterval = 0;

// Maximum time allowed between taps (in milliseconds). If exceeded, the next tap is considered the "first" tap.
int maxTimeBetweenTaps = 2000; // 2 seconds for example

// List to store the intervals between taps
ArrayList<Integer> tapIntervals = new ArrayList<Integer>();
int numberOfTapsToAverage = 5;

void setup() {
  size(300, 300);
  fill(255, 0, 0);
  noStroke();
  time = millis();
}

void draw() {
  background(255);

  if (millis() - time > interval ) {
    ellipse(width/2, height/2, 50, 50);
    beats++;
    time = millis();
  }

  text(beats, 30, height - 25);
  text("BPM: " + bpm, 30, height - 50);
}

void keyPressed() {
  int currentTapTime = millis();
  
  // If the time between the current tap and the last tap exceeds maxTimeBetweenTaps, reset lastTapTime and clear the tapIntervals list
  if (currentTapTime - lastTapTime > maxTimeBetweenTaps) {
    lastTapTime = 0;
    tapIntervals.clear();
  }
  
  // If it's not the first tap, calculate the BPM
  if (lastTapTime != 0) {
    tapInterval = currentTapTime - lastTapTime;
    tapIntervals.add(tapInterval);
    
    // If we have enough taps, calculate the average BPM
    if (tapIntervals.size() == numberOfTapsToAverage) {
      int totalInterval = 0;
      for (int i = 0; i < tapIntervals.size(); i++) {
        totalInterval += tapIntervals.get(i);
      }
      int averageInterval = totalInterval / numberOfTapsToAverage;
      bpm = 60000.0 / averageInterval;
      interval = averageInterval;
			beats = 0;
      
      // Remove the oldest tap interval to make room for the next one
      tapIntervals.remove(0);
    }
  }
  
  lastTapTime = currentTapTime;
}