// C++ code
#define LED 2
#define trig 4
#define echo 7
#define piezo 8
long distance;
unsigned long duration;
unsigned long startDetect = 0;
unsigned long previousMillis = 0;
const long timeLimit = 10000;
boolean alarm = false;


void setup()
{
  pinMode(LED, OUTPUT);
  pinMode(trig, OUTPUT);
  pinMode(echo, INPUT);
  pinMode(piezo, OUTPUT);
  Serial.begin(9600);
  delay(10000);
}

void loop()
{
  digitalWrite(trig, LOW);
  digitalWrite(trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig, LOW);
  duration = pulseIn(echo, HIGH, 30000);
  distance = duration * 0.034 / 2;
  Serial.print("Distance: ");
  Serial.println(distance);

  if (distance == 0 || distance > 200)
  {
    if (alarm)
    {
      Serial.println("Out of range");
    }
    alarm = false;
    digitalWrite(LED, LOW);
    noTone(piezo);
  }
  else // Object closer than 200 cm
  {
    if (!alarm)
    {
      Serial.println("Object detected");
      startDetect = millis();
      alarm = true;
    }
    else
    {
      unsigned long currentMillis = millis();
      if (currentMillis - startDetect >= timeLimit) {
        digitalWrite(LED, HIGH);
        tone(piezo, 200);
        delay(500);
        digitalWrite(LED, LOW);
        noTone(piezo);
        delay(500);  // Half-second delay between beeps
      }
    }
  }
}