#include <Wire.h>               // For I2C communication
#include <LiquidCrystal_I2C.h>  // Library for LCD with I2C

// Create LCD object with I2C address (usually 0x27 or 0x3F)
LiquidCrystal_I2C lcd(0x27, 16, 2);

// Ultrasonic Sensor pins
const int trigPin = 9;
const int echoPin = 10;

// LED and Buzzer pins
const int ledPin = 6;
const int buzzerPin = 7;

void setup() {
  Serial.begin(9600);

  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(ledPin, OUTPUT);
  pinMode(buzzerPin, OUTPUT);

  // Initialize LCD
  lcd.init();
  lcd.backlight(); // Turn on backlight
  lcd.setCursor(0, 0);
  lcd.print("Ultrasonic Test");
  delay(2000);
}

void loop() {
  // Send trigger pulse
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Read echo pulse
  long duration = pulseIn(echoPin, HIGH);

  // Calculate distances
  float distanceCM = duration * 0.034 / 2;
  float distanceInches = distanceCM / 2.54;

  // Display on LCD
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("CM: ");
  lcd.print(distanceCM, 1);

  lcd.setCursor(0, 1);
  lcd.print("In: ");
  lcd.print(distanceInches, 1);

  // LED and Buzzer alert
  if (distanceCM <= 10) {
    digitalWrite(ledPin, HIGH);

    // Beep like a bomb alert
    for (int i = 0; i < 3; i++) {
      tone(buzzerPin, 1000);
      delay(100);
      noTone(buzzerPin);
      delay(100);
    }
  } else {
    digitalWrite(ledPin, LOW);
    noTone(buzzerPin);
  }

  delay(500);
}