long duration;
float distance;
float lastDistance = 0;
unsigned long lastTime = 0;

int T = 9;
int E = 10;
int buttonPin = 7; // Knopf an Pin 7
bool isMeasuring = false;

void setup() {
  Serial.begin(9600);
  pinMode(T, OUTPUT);
  pinMode(E, INPUT);
  pinMode(buttonPin, INPUT); // Knopf mit internem Pullup-Widerstand
}

void loop() {
  // Prüfen, ob der Knopf gedrückt wurde
  if (digitalRead(buttonPin) == HIGH) {
    isMeasuring = true;  // Messung starten
    Serial.println("Messung gestartet...");
    delay(300); // Kurze Wartezeit, um Prellen zu vermeiden
  }

  if (isMeasuring) {
    unsigned long currentTime = millis();

    // Ultraschallsensor auslösen
    digitalWrite(T, LOW);
    delayMicroseconds(2);
    digitalWrite(T, HIGH);
    delayMicroseconds(10);
    digitalWrite(T, LOW);

    // Echo-Zeit messen
    duration = pulseIn(E, HIGH);
    distance = duration * 0.034 / 2;

    // Geschwindigkeit berechnen (falls nicht erste Messung)
    if (lastTime > 0) {
      float deltaS = lastDistance - distance;
      float deltaT = (currentTime - lastTime) / 1000.0;
      float velocity = deltaS / deltaT;

      Serial.print("Zeit: ");
      Serial.print(currentTime);
      Serial.print(" ms, Abstand: ");
      Serial.print(distance);
      Serial.print(" cm, Geschwindigkeit: ");
      Serial.print(velocity);
      Serial.println(" cm/s");
    } else {
      Serial.print("Zeit: ");
      Serial.print(currentTime);
      Serial.print(" ms, Abstand: ");
      Serial.println(distance);
    }

    // Werte speichern
    lastDistance = distance;
    lastTime = currentTime;

    delay(100); // 10 Messungen pro Sekunde
  }
}