#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2); // I2C address 0x27
int trigPin = 13; // TRIG pin
int echoPin = 12; // ECHO pin
float duration_us, distance_cm;

const int buzzerPin = 10;
 
//const int buttonPin = 7;   //
const int buttonPin = 2;


 
long duration;
 
int distance;
 
bool alertEnabled = true;
bool prev_alertEnabled = true;

void buttonISR() {
 
 if(prev_alertEnabled == alertEnabled)
 {

  
  alertEnabled = !alertEnabled;
   delay(500);
 
  
 
}
}
 



void setup() {
  pinMode(trigPin, OUTPUT);
 
  pinMode(echoPin, INPUT);
 
  pinMode(buzzerPin, OUTPUT);
 
  pinMode(buttonPin, INPUT_PULLUP); // Using internal pull-up resistor
 
  lcd.init();
 
  lcd.backlight();
 
  lcd.setCursor(0, 0);
 
  lcd.print("Distance:");
 
  Serial.begin(9600);
  attachInterrupt(digitalPinToInterrupt(buttonPin), buttonISR, LOW);

}

void loop() 
{
   
 
  // Clear the trigPin by setting it LOW
 
  digitalWrite(trigPin, LOW);
 
  delayMicroseconds(2);
 
 
 
  // Set the trigPin HIGH for 10 microseconds
 
  digitalWrite(trigPin, HIGH);
 
  delayMicroseconds(10);
 
  digitalWrite(trigPin, LOW);
 
 
 
  // Read the echoPin and calculate the distance
 
  duration = pulseIn(echoPin, HIGH);
 
  distance = duration * 0.034 / 2;
 
 
 
  // Display the distance on the LCD
 
  lcd.setCursor(0, 1);
 
  lcd.print("                "); // Clear previous data
 
  lcd.setCursor(0, 1);
 
  lcd.print(distance);
 
  lcd.print(" cm");

   
  // Check the distance and activate the buzzer if alert is enabled
  
 
  
  if (alertEnabled == false) {
    
    lcd.setCursor(0, 1);
    lcd.print("Off       ");
  
 
  }


  buzzerControl();
  
  delay(500); // Wait for a short period before the next measurement
  prev_alertEnabled = alertEnabled;
 

 
}

void buzzerControl(){
   if (alertEnabled && distance < 20) { // You can adjust the threshold distance
 
    digitalWrite(buzzerPin, HIGH);
    Serial.println("buzzer ON "); 
 
  } else {
 
    digitalWrite(buzzerPin, LOW);
    Serial.println("buzzer OFF "); 
 
  }
  delay(500);


}