#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2); // I2C address 0x27, 16 columns, 2 rows

#define TRIG_PIN 23    // ESP32 pin GPIO23 connected to Ultrasonic Sensor's TRIG pin
#define ECHO_PIN 19    // ESP32 pin GPIO19 connected to Ultrasonic Sensor's ECHO pin
#define BUZZER_PIN 18  // ESP32 pin GPIO18 connected to Buzzer

float duration_us, distance_cm;

void setup() {
  lcd.init();               // initialize the lcd
  lcd.backlight();          // turn on the backlight

  pinMode(TRIG_PIN, OUTPUT); // set TRIG pin as output
  pinMode(ECHO_PIN, INPUT);  // set ECHO pin as input
  pinMode(BUZZER_PIN, OUTPUT); // set BUZZER pin as output
}

void loop() {
  // generate a 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 in cm
  distance_cm = 0.017 * duration_us;

  lcd.clear();
  lcd.setCursor(0, 0); // start printing at the first row
  lcd.print("Distance: ");
  lcd.print(distance_cm);

  // Activate the buzzer if the distance is less than a certain threshold
  if (distance_cm < 5) { // if object is within 10 cm
    digitalWrite(BUZZER_PIN, HIGH); // turn on the buzzer
  } else {
    digitalWrite(BUZZER_PIN, LOW);  // turn off the buzzer
  }

  delay(500); // wait for 500ms before next measurement
}