// Pin definitions for the Ultrasonic Sensor
const int TRIG_PIN = 25;
const int ECHO_PIN = 26;

// Pin definitions for the LEDs
const int GREEN_LED = 32;
const int YELLOW_LED = 33;
const int RED_LED = 18;

// Variables for distance measurement
long duration;
float distance_cm;

void setup() {
  Serial.begin(115200);
  
  // Set up sensor pins
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  
  // Set up LED pins
  pinMode(GREEN_LED, OUTPUT);
  pinMode(YELLOW_LED, OUTPUT);
  pinMode(RED_LED, OUTPUT);
}

void loop() {
  // Clear the TRIG pin and send the ultrasonic pulse
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  
  // Measure the duration of the echo pulse
  duration = pulseIn(ECHO_PIN, HIGH);
  
  // Calculate the distance in cm
  distance_cm = duration * 0.034 / 2.0;

  // Control the LEDs based on the distance using if-else if-else logic
  if (distance_cm > 100) {
    // Distance > 100 cm: Green LED on, others off
    digitalWrite(GREEN_LED, HIGH);
    digitalWrite(YELLOW_LED, LOW);
    digitalWrite(RED_LED, LOW);
  } else if (distance_cm >= 30 && distance_cm <= 100) {
    // 30 <= Distance <= 100 cm: Yellow LED on, others off
    digitalWrite(GREEN_LED, LOW);
    digitalWrite(YELLOW_LED, HIGH);
    digitalWrite(RED_LED, LOW);
  } else if (distance_cm < 30) {
    // Distance < 30 cm: Red LED on, others off
    digitalWrite(GREEN_LED, LOW);
    digitalWrite(YELLOW_LED, LOW);
    digitalWrite(RED_LED, HIGH);
  }
  
  // Print the distance to the Serial Monitor
  Serial.print("Distance: ");
  Serial.print(distance_cm);
  Serial.println(" cm");
  
  // Wait before the next measurement
  delay(500);
}