#define TRIG_PIN 5
#define ECHO_PIN 18
#define RED_LED 21
#define GREEN_LED 19
#define THRESHOLD 100 // Distance threshold in cm

void setup() {
  Serial.begin(115200);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(RED_LED, OUTPUT);
  pinMode(GREEN_LED, OUTPUT);
}

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

  long duration = pulseIn(ECHO_PIN, HIGH);
  float distance = (duration * 0.0343) / 2; // Convert time to distance in cm

  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  if (distance <= THRESHOLD) {
    digitalWrite(RED_LED, HIGH);
    digitalWrite(GREEN_LED, LOW);
    Serial.println("Object is NEAR!");
  } 
  else if(distance > THRESHOLD) {
    digitalWrite(RED_LED, LOW);
    digitalWrite(GREEN_LED, HIGH);
    Serial.println("Object is FAR!");
  }
  else {
    digitalWrite(RED_LED, LOW);
    digitalWrite(GREEN_LED, LOW);
    
  }

  delay(500);
}