/*
  HC-SR04 Ultrasonic Sensor Example.

  Turn the LED on when an object is within 100cm range.

  Copyright (C) 2021, Uri Shaked
*/
#include <LiquidCrystal_I2C.h>
#define ECHO_PIN 2
#define TRIG_PIN 3
LiquidCrystal_I2C lcd(0x27, 20, 4);

void setup() {
  Serial.begin(115200);
  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  lcd.init();
  lcd.backlight();
  lcd.setCursor(1, 0);
  lcd.print("Inches     cm");
}

float readDistanceCM() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  int duration = pulseIn(ECHO_PIN, HIGH);
  return duration * 0.034 / 2;
}

void loop() {
  float distance = readDistanceCM();

  bool isNearby = distance < 100;
  digitalWrite(LED_BUILTIN, isNearby);

  Serial.print("Measured distance: ");
  Serial.println(readDistanceCM());

  delay(100);
  lcd.clear();
  lcd.setCursor(2,1);
  lcd.print(distance/2.54);
  lcd.setCursor(11, 1);
  lcd.print(distance);
  delay(100);
}