#include <Wire.h>
#include <LiquidCrystal_I2C.h>

const int trigPin = 9; // Pin for sensor, trig pin transmits signal to object
const int echoPin = 10; // Pin for sensor, echo pin receives the signal
const int ledPin = 13; // LED pin on Arduino
const int buzzerPin = 2; // Buzzer pin on Arduino
long duration; // Distance variable
int distance;
const int safeDistance = 150; // Set the safe distance threshold

LiquidCrystal_I2C lcd(0x27, 16, 2); // Change the address if needed

void setup() {
    Serial.begin(9600);  
    pinMode(trigPin, OUTPUT); 
    pinMode(echoPin, INPUT);
    pinMode(ledPin, OUTPUT);  
    pinMode(buzzerPin, OUTPUT);
    
    lcd.begin(16, 2); // Initialize the LCD
    lcd.backlight(); // Turn on the LCD backlight
}

void loop() {
    digitalWrite(trigPin, LOW);
    delayMicroseconds(2);
    digitalWrite(trigPin, HIGH); // Trigger pin's output pulse
    delayMicroseconds(10); // Short pulse for accuracy
    digitalWrite(trigPin, LOW);
    
    duration = pulseIn(echoPin, HIGH); // Measure pulse duration
    distance = duration * 0.034 / 2; // Calculate distance in cm

    lcd.clear(); // Clear the LCD
    lcd.setCursor(0, 0); // Set cursor to first line
    lcd.print("Distance: ");
    lcd.print(distance); // Print distance in cm
    lcd.print(" cm");

    if (distance <= 150 && distance >= 0) { // If distance is within range
        digitalWrite(ledPin, HIGH); // Light LED
        tone(buzzerPin, 500, 120); // Play tone
        
        if (distance < safeDistance) { // If person is too close
            lcd.setCursor(0, 1); // Set cursor to second line
            lcd.print("Go back: ");
            lcd.print(safeDistance - distance); // Distance to go back
            lcd.print(" cm");
        } 
    } else {
        digitalWrite(ledPin, LOW); // Turn off LED
        noTone(buzzerPin); // Stop buzzer sound
        lcd.setCursor(0, 1);
        lcd.print(" Safe Distance!"); // Clear previous message
    }
    
    delay(100); // Shorter delay for quicker response
}