//import libraries for display
#include <LiquidCrystal.h>

//define lcd with LiquidCrystal library
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

const int pingPin = 7; // Trigger Pin of Ultrasonic Sensor
const int echoPin = 6; // Echo Pin of Ultrasonic Sensor
// Connect Ultrasonic sensor VCC to 5 V, and Gnd to 0 V
int duration;

//for disatnce
double distance;

//value of m and C required for linear equation
double m = 0.0170943;
double c = 0.0193299;

//LED pin
int ledPin = 9;

void setup() {

  //initialize LCD
  lcd.begin(16, 2);
  lcd.print("Initializing...");

  //set output mode for LED
  pinMode(ledPin, OUTPUT);

  Serial.begin(9600); // Starting Serial Terminal
  delay(3000);
}
void loop() {
  // Ultrasound sensor ping
  pinMode(pingPin, OUTPUT);
  digitalWrite(pingPin, LOW);
  delayMicroseconds(2);
  digitalWrite(pingPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(pingPin, LOW);
  // Ultrasound sensor echo catch
  pinMode(echoPin, INPUT);
  duration = pulseIn(echoPin, HIGH);

  distance = m * duration + c;
  // Send distance data to Serial port
  // Serial.println(distance);

  //print distance in LCD
  lcd.clear();
  lcd.print("Distance: ");
  lcd.print((int)distance);
  lcd.print("cm");

  if (distance < 20) {
    digitalWrite(ledPin, HIGH);
  } else {
    digitalWrite(ledPin, LOW);
  }

  // Wait before next ping
  delay(250);
}