#include <ESP32Servo.h>

#define TRIG_PIN 23 // ESP32 pin GPIO23 connected to Ultrasonic Sensor's TRIG pin
#define ECHO_PIN 22 // ESP32 pin GPIO22 connected to Ultrasonic Sensor's ECHO pin
#define SERVO_PIN 5 // ESP32 pin GPIO25 connected to Servo Motor's pin
#define DISTANCE_THRESHOLD_1 50 // centimeters for first range
#define DISTANCE_THRESHOLD_2 100 // centimeters for second range
#define LED_PIN 14 // ESP32 pin GPIO14 (Red LED)

Servo servo; // create servo object to control a servo

float duration_us, distance_cm; // variables to store duration and distance

void setup() {
  Serial.begin(9600); // initialize serial port
  pinMode(TRIG_PIN, OUTPUT); // set ESP32 pin to output mode
  pinMode(ECHO_PIN, INPUT); // set ESP32 pin to input mode
  servo.attach(SERVO_PIN); // attaches the servo on pin to the servo object
  servo.write(0); // set initial position of servo
  pinMode(LED_PIN, OUTPUT); // set ESP32 pin to output mode
}

void loop() {
  // generate 10-microsecond pulse to TRIG pin
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  // measure duration of pulse from ECHO pin
  duration_us = pulseIn(ECHO_PIN, HIGH);
  // calculate the distance
  distance_cm = 0.017 * duration_us;

  if (distance_cm < DISTANCE_THRESHOLD_1)
  {
    servo.write(360);
    digitalWrite(LED_PIN, HIGH);
    delay(100);
  }
  else if (distance_cm < DISTANCE_THRESHOLD_2)
  {
    servo.write(-360);
    digitalWrite(LED_PIN, LOW);
    delay(100);
  }
}