// LAB 3 ; TASK 2 ; ADRIANA SARAH BINTI AHMAD FAIZA ; 52224123439

int trigPin = 9;
int echoPin = 10;
int buzzerPin = 11;
int distanceThreshold = 80; // distance threshold in cm

void setup() {
  Serial.begin(9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(buzzerPin, OUTPUT);
}

void loop() {
  // generate ultrasonic pulse
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // read the echo pulse
  long duration = pulseIn(echoPin, HIGH);
  // Calculate distance in cm
  int distance = duration * 0.034 / 2;

  // print distance to serial monitor
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  // check if distance is below threshold and control the buzzer
  if (distance < distanceThreshold) {
    tone(buzzerPin, 2000);
  } else {
    noTone(buzzerPin);
  }

  delay(100);
}