Button Timing

button_timing.ino

int buttonPin = 2;

int buttonState;
unsigned long timestamp;

void setup() {
  // prepare ports for communication
  pinMode(buttonPin, INPUT);
  Serial.begin(9600);
  
  // set initial timer and button state values
  timestamp = millis();
  buttonState = digitalRead(buttonPin);
}

void loop() {
  // if the button's state changed (pressed -> released or released -> pressed)
  if (digitalRead(buttonPin) != buttonState) {
    // if the button _was_ being pressed before...
    if (buttonState == LOW) {
      // print out timing (note that we have to convert the numeric expression to a String for this to work
      Serial.print("Button was pressed for " + String(millis() - timestamp) + " milliseconds\n");
      // flip state to opposite (released)
      buttonState = HIGH;
    // ...otherwise, the button _was_ released before
    } else {
      Serial.print("Button was released for " + String(millis() - timestamp) + " milliseconds\n");
      buttonState = LOW;
    }
    // reset the timer for the new state
    timestamp = millis();
  }
}