#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   "); 
}