#include <LiquidCrystal.h> // includes the LiquidCrystal Library

// Creates an LCD object. Parameters: (rs, enable, d4, d5, d6, d7)
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

const int trigPin = 9;    // Pin for the trigger of the ultrasonic sensor
const int echoPin = 8;    // Pin for the echo of the ultrasonic sensor

long duration;            // Duration variable for pulse timing
int distanceCm, distanceInch; // Variables for distance in cm and inches

void setup() {
  lcd.begin(16, 2); // Initializes the interface to the LCD screen and specifies the dimensions (width and height) of the display
  
  // Initialize the ultrasonic sensor pins
  pinMode(trigPin, OUTPUT);  // Set the trigPin as an output
  pinMode(echoPin, INPUT);   // Set the echoPin as an input
}

void loop() {
  digitalWrite(trigPin, LOW);           // Ensure the trigger pin is low
  delayMicroseconds(2);                  // Wait for 2 microseconds
  digitalWrite(trigPin, HIGH);          // Send a high pulse for 10 microseconds
  delayMicroseconds(10);                
  digitalWrite(trigPin, LOW);           // Ensure the trigger pin is low again
  
  // Measure the duration of the pulse received at echoPin
  duration = pulseIn(echoPin, HIGH);

  // Calculate the distance in centimeters and inches
  distanceCm = duration * 0.034 / 2;   // Speed of sound is 0.034 cm per microsecond
  distanceInch = duration * 0.0133 / 2; // Convert to inches

  // Display the distance in cm on the LCD
  lcd.setCursor(0, 0);                 // Set the cursor to the first row
  lcd.print("Distance: ");              // Print the string "Distance"
  lcd.print(distanceCm);                // Print the distance in cm
  lcd.print(" cm");
  
  delay(10); // Small delay for screen refresh

  // Display the distance in inches on the second row of the LCD
  lcd.setCursor(0, 1);                 // Set the cursor to the second row
  lcd.print("Distance: ");
  lcd.print(distanceInch);             // Print the distance in inches
  lcd.print(" inch");

  delay(10); // Small delay for screen refresh
}