#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);   // Mange displays bruger 0x27, ellers prøv 0x3F

const int trigPin = 9;
const int echoPin = 10;

void setup() {
  pinMode(trigPin, OUTPUT); // sender signal ud
  pinMode(echoPin, INPUT);

  lcd.init();
  lcd.backlight();
  lcd.setCursor(0,0);
  lcd.print("Distance:");
}

void loop() {
  long duration;
  float distance;

  // Send trigger-puls
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Læs echo
  duration = pulseIn(echoPin, HIGH);

  // Omregn til cm (lydens hastighed ~ 0.034 cm/us)
  distance = duration * 0.034 / 2;

  lcd.setCursor(0,1);
  lcd.print("                "); // Ryd linje
  lcd.setCursor(0,1);
  lcd.print(distance);
  lcd.print(" cm");

  delay(300);
}