const byte inPin = 3;
unsigned long timeDifference = 0;
unsigned long lastHigh = 0;
unsigned long actHigh;
byte lastState = HIGH;
byte state;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  pinMode(inPin, INPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
 state = debounced();
 if (lastState != state) {
   if (state) {
     actHigh = millis();
     if (lastHigh > 0) {
       timeDifference = actHigh - lastHigh;
       Serial.println(timeDifference);
     }
     lastHigh = actHigh;
   }
   lastState = state;
 } 
}

byte debounced(){
   static unsigned long lastTime = 0;
   static byte lastS = HIGH;
   static byte ReturnState = HIGH;
   byte actState = digitalRead(inPin);
   if (actState != lastS){
     lastS = actState;
     lastTime = millis();
   }
   if (millis()-lastTime > 30) {
     ReturnState = actState;
   }
   return ReturnState;
}