#include <LiquidCrystal.h>
LiquidCrystal lcd(12, 11, 10, 9, 8, 7);
const int echoPin = 2; // attach pin D2 Arduino to pin Echo of HC-SR04
const int trigPin = 3; //attach pin D3 Arduino to pin Trig of HC-SR04
// defines variables
long duration; // variable for the duration of sound wave travel
int distance; // variable for the distance measurement
void setup() {
pinMode(trigPin, OUTPUT); // Sets the trigPin as an OUTPUT
pinMode(echoPin, INPUT); // Sets the echoPin as an INPUT
lcd.begin(16, 2);
// you can now interact with the LCD, e.g.:
lcd.print("Hello world!");
lcd.setCursor(0,1);
lcd.print("Display demo.");
delay(1000);
lcd.begin(16, 2); // Reset the LCD
lcd.print("Distance:");
}

void loop() {
// Clears the trigPin condition
digitalWrite(trigPin, LOW);
delayMicroseconds(2);
// Sets the trigPin HIGH (ACTIVE) for 10 microseconds
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);
// Reads the echoPin, returns the sound wave travel time in microseconds
duration = pulseIn(echoPin, HIGH);
// Calculating the distance
distance = duration * 0.034 / 2; // Speed of sound wave divided by 2 (go and back)

// Displays the distance on the LCD
lcd.setCursor(0,1); // update only the second line
lcd.print(distance); // display the distance
lcd.print(" cm ");
}