const int buttonPin = 5;
unsigned long lastPressTime;
int buttonState = 0;
int singlePress = 0;

void setup() {
  pinMode(buttonPin, INPUT_PULLUP);

  lastPressTime = millis();
  Serial.begin(9600);
}

void loop() {
  if (!digitalRead(buttonPin) == HIGH && buttonState == 0) {
    unsigned long currentPressTime = millis();

    //two presses within 500ms
    if (currentPressTime - lastPressTime < 500) {
      singlePress = 0;
      //Do double press action
      Serial.println("double");
    } else {
      singlePress = 1;
    }

    //update the last pressed time
    lastPressTime = currentPressTime;
    buttonState = 1;
  } else if (!digitalRead(buttonPin) == LOW) {
    buttonState = 0;
  }

  //check if 500ms have passed with no second button press
  //if (singlePress == 1 && lastPressTime  - millis() > 500) {
    if (singlePress == 1 &&  millis() - lastPressTime  > 500) {
    singlePress = 0;
    //DO single press stuff
    Serial.println("single");
  }
}