/*
  Forum: https://forum.arduino.cc/t/speed-measurement-via-button/1213924
  Wokwi: https://wokwi.com/projects/387533742096207873

  2024/01/21
  ec2021

*/

const byte buttonPin = 4;
unsigned long lastPressedTime = 0;
 
void setup() {
  pinMode(buttonPin, INPUT_PULLUP);
  Serial.begin(115200);
  Serial.println("Start ");
}

void loop() {
  if (buttonPressed()){
    if (lastPressedTime > 0){
      unsigned long difference = millis()-lastPressedTime;
      Serial.print("Time difference: ");
      Serial.println(difference);
    }
    lastPressedTime = millis();
  }
}

boolean buttonPressed(){
static unsigned long lastChange = 0;
static byte lastState = LOW;
static byte state;
   byte actState = digitalRead(buttonPin);
   if (actState != lastState) {
      lastState = actState;
      lastChange = millis();
   }
   if (state != actState && millis()-lastChange > 20){
     state = actState;
     return !state; // Returns true only when state changes from HIGH to LOW
   }
  return false;
}