#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27,16,4);

const int trigPin = 6;
const int echoPin = 4;
const int buzzerPin = 11;
const int greenLED = 7;
const int yellowLED = 10;
const int redLED = 13;

//Setup LCD
void setup (){
lcd.init();
lcd.backlight();

//Setup all pin LCD,buzzer and LED
pinMode (trigPin, OUTPUT);
pinMode (echoPin, INPUT);
pinMode (buzzerPin, OUTPUT);
pinMode (greenLED, OUTPUT);
pinMode (yellowLED, OUTPUT);
pinMode (redLED, OUTPUT);
}

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

  //Calculate the duration it takes for pulse to return
  long duration = pulseIn(echoPin, HIGH);
  
  //Calculate distance in cm
  int distance = duration * 0.034/2;

  if (distance < 50) { //close range
    tone(buzzerPin, 1000); //continuous sound
    digitalWrite(buzzerPin, HIGH);
    digitalWrite(redLED, HIGH); //Blink red LED
    digitalWrite(yellowLED, LOW);
    digitalWrite(greenLED, LOW);
    delay(100); //Blink duration
    digitalWrite(buzzerPin, LOW); //buzzer pulse
    digitalWrite(redLED, LOW); //LED blinking
    delay(100); }

  else if (distance >= 50 && distance <=100 ) { //mid range
    tone(buzzerPin, 600); //continuous sound
    digitalWrite(buzzerPin, HIGH);
    digitalWrite(redLED, LOW); 
    digitalWrite(yellowLED, HIGH); //Blink yellow LED
    digitalWrite(greenLED, LOW);
    delay(250); //Blink duration
    digitalWrite(buzzerPin, LOW); //buzzer pulse 
    digitalWrite(yellowLED, LOW);
    delay(250); }
  
  else if (distance >= 100 && distance <=200) {
    tone(buzzerPin, 300); //continuous sound
    digitalWrite(buzzerPin, HIGH);
    digitalWrite(redLED, LOW); 
    digitalWrite(yellowLED, LOW);
    digitalWrite(greenLED, HIGH); }

  else {
    noTone(buzzerPin); // Stop buzzer if out of range
    digitalWrite(greenLED, LOW);
    digitalWrite(yellowLED, LOW);
    digitalWrite(redLED, LOW); }

  //Display distance in LCD
  lcd.setCursor(0,0);
  lcd.print("Distance: ");
  lcd.print(distance);
  lcd.print(" cm");

  }