Ultrasonic distance on an LCD (TRIG 2, ECHO 3), on an Arduino Uno

// Distance on an LCD: an HC-SR04 on pins 2 and 3.
//
//   HC-SR04 TRIG -> pin 2   ECHO -> pin 3   VCC -> 5V   GND -> GND
//   LCD RS -> pin 4    LCD E -> pin 6
//   LCD D4 -> pin 10   D5 -> pin 11   D6 -> pin 12   D7 -> pin 13
//   LCD RW, VSS, K -> GND     VDD, A -> 5V
//   LCD V0 (contrast) -> GND here; on the bench, the middle leg of a pot
//
// A 10 microsecond pulse on TRIG sends a burst of sound; ECHO then stays HIGH
// for as long as the sound takes to come back. pulseIn() measures that time,
// and sound covers a centimeter there and back in about 58 microseconds.
//
// Drag the distance slider on the sensor.

#include <LiquidCrystal.h>

const int TRIG = 2;
const int ECHO = 3;

LiquidCrystal lcd(4, 6, 10, 11, 12, 13);

long distanceCm() {
  digitalWrite(TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG, LOW);
  long echo = pulseIn(ECHO, HIGH, 30000UL);
  return echo / 58;
}

void setup() {
  pinMode(TRIG, OUTPUT);
  pinMode(ECHO, INPUT);
  lcd.begin(16, 2);
  lcd.print("Distance:");
  Serial.begin(9600);
  Serial.println("Mokxi Uno: HC-SR04 on pins 2 and 3, LCD on 4, 6 and 10 to 13");
}

void loop() {
  long cm = distanceCm();
  lcd.setCursor(0, 1);
  lcd.print("                ");
  lcd.setCursor(0, 1);
  if (cm == 0) {
    lcd.print("out of range");
  } else {
    lcd.print(cm);
    lcd.print(" cm");
  }
  Serial.print(cm);
  Serial.println(" cm");
  delay(500);
}