#include <LiquidCrystal.h>

const int RS = 23, EN = 22, D4 = 21, D5 = 19, D6 = 18, D7 = 5;
const int TRIG_PIN = 17;
const int ECHO_PIN = 16;

LiquidCrystal lcd(RS, EN, D4, D5, D6, D7);

// function to measure distance
int getDistance() {
  // send trigger pulse
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  // read pulse duration
  long duration = pulseIn(ECHO_PIN, HIGH);
  // calculate distance
  long distance = duration * 0.0343 / 2;
  return (int)distance + 0.5;
}

void printRange(int range)  {
  lcd.setCursor(2, 0);
  lcd.print("Range:");
  lcd.setCursor(6, 1);
  lcd.print(range);
  lcd.print(" cm    ");
}

void showSplash() {
  lcd.setCursor(2, 0);
  lcd.print("HC-SR04 Demo");
  lcd.setCursor(6, 1);
  lcd.print("V1.0");
  delay(2000);
  lcd.clear();
  Serial.println("\nHC-SR04 Demo");
}

void setup() {
  Serial.begin(115200);
  lcd.begin(16, 2);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  showSplash();
}

void loop() {
  int distance = getDistance();
  printRange(distance);
  delay(1000);
}