#include <LiquidCrystal_I2C.h>

// set the LCD number of columns and rows
const int lcdColumns = 16;
const int lcdRows = 2;

// set LCD address, number of columns and rows
// if you don't know your display address, run an I2C scanner sketch
LiquidCrystal_I2C lcd(0x27, lcdColumns, lcdRows); 

// Indicator LEDs
const int ledPinRed = 12;
const int ledPinGreen = 13;

// Ultra Sonic Sensor Pin
const int trigPin = 5;
const int echoPin = 18;

//define sound speed in cm/uS
#define SOUND_SPEED 0.034

long duration;
int distanceCm;


void setup() {
  // LED Setup
  pinMode (ledPinRed, OUTPUT);
  pinMode (ledPinGreen, OUTPUT);

  // initialize LCD
  lcd.init();                     
  lcd.backlight();  // turn on LCD backlight 

  // Ultra Sonic Sensor 
  Serial.begin(115200); // Starts the serial communication
  pinMode(trigPin, OUTPUT); // Sets the trigPin as an Output
  pinMode(echoPin, INPUT); // Sets the echoPin as an Input
}



void loop() {
  // Ultra Sonic Sensor
  digitalWrite(trigPin, LOW); // Clears the trigPin
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH); // Sets the trigPin on HIGH state for 10 micro seconds
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW); // Clears the trigPin
  
  // Reads Ultrasonic Sensor
  duration = pulseIn(echoPin, HIGH);
  distanceCm = (int) duration * SOUND_SPEED/2; // Calculate the distance

  // LED Indication based on distance
  if(distanceCm >= 200) { // Adjust threshold based on sensor range
    digitalWrite (ledPinRed, LOW);
    digitalWrite (ledPinGreen, HIGH);
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Present");
  } else {
    digitalWrite (ledPinRed, HIGH);
    digitalWrite (ledPinGreen, LOW);
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Not Present");
  }

  delay(1000);
}