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

LiquidCrystal_I2C lcd(0x27, 16, 2);

const int trigger = 9;   
const int echo = 10;   
const int buzzer = 11; 
const int led = 13; 

void setup() {
  pinMode(trigger, OUTPUT);
  pinMode(echo, INPUT);
  pinMode(buzzer, OUTPUT);
  pinMode(led, OUTPUT);
  Serial.begin(9600); 


    lcd.init();      // Initialize the LCD
  lcd.backlight(); // Turn on the backlight
 
}

void loop() {
  digitalWrite(trigger, LOW);
  delayMicroseconds(5);
  
  digitalWrite(trigger, HIGH);
  delayMicroseconds(13);
  digitalWrite(trigger, LOW);
  
  long duration = pulseIn(echo, HIGH);
  
  long distance = (duration * 0.0343) / 2;
  
  Serial.print("Sensor Distance: ");
  Serial.println(distance);
    //Distance = (Time x SpeedOfSound) / 2.
  //Sound travels about 0.0343 CM per microsecond so multiply the duration by 0.0343 to get round-trip (out and back) centimeters.
  //1 m/s = 100/1000000 = 0.0001 cm/μs

 //343 m/s = 0.0001 * 343 = 0.0343 cm/μs
 if (distance < 40) {
      Serial.print("OBSTACLE DETECTED \n");
    tone(buzzer, 1000); 
  } else {
    noTone(buzzer);  
  }
  if(distance>40){
    Serial.print("NO OBSTACLE DETECTED \n");
digitalWrite(led, HIGH); 

  }
  else{
    digitalWrite(led, LOW); 

  }

   lcd.setCursor(0, 0);
  lcd.print("OBJ DISTANCE ");
  lcd.setCursor(0, 1);
  lcd.print(distance);
  lcd.setCursor(4, 1);
  lcd.print("cm");

 
  delay(500); 
}

  
 /* if (distance < 75) {
    tone(buzzer, 1000); 
  } else {
    noTone(buzzer);  
  }
  if(distance>75){
digitalWrite(led, HIGH); 

  }
  else{
    digitalWrite(led, LOW); 

  }

   lcd.setCursor(0, 0);
  lcd.print("distance");
  lcd.setCursor(0, 1);
  lcd.print(distance);
 
  delay(500); 
}
*/