int pin = 7;
int timeout = 4;

    unsigned long duration;


    void setup() {

      Serial.begin(9600);

      pinMode(pin, INPUT_PULLUP);

    }


    void loop() {

      duration = pulseInLong(pin, LOW, timeout*1000000);
      Serial.print(duration);

      // warten bis wieder high

      while (digitalRead(pin) == LOW) {
        delay(100);
      }
      Serial.println(" ready");


    }