#define ECHO_PIN 8
#define TRIG_PIN 10
const int BUZZER_PIN = 9;

long duration;
int distance;

void setup() {
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(BUZZER_PIN, OUTPUT);

  Serial.begin(9600);
  Serial.println("Ultrasonic Sensor HC-SR04 Test");
  Serial.println("with Arduino UNO R3");
}

void loop() {
  measureDistance();
  displayDistance();
  checkDistanceAndAlert();
}

void measureDistance() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  duration = pulseIn(ECHO_PIN, HIGH);
  distance = duration * 0.034 / 2;
}

void displayDistance() {
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");
}

void checkDistanceAndAlert() {
  if (distance < 5) {
    tone(BUZZER_PIN, 500);
    delay(1000);
    noTone(BUZZER_PIN);
  }
}