/*
  HC-SR04 Ultrasonic Sensor Example.

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

  Copyright (C) 2021, Uri Shaked
*/
#include <LiquidCrystal.h>

LiquidCrystal lcd(12, 11, 10, 9, 8, 7);
#define ECHO_PIN 2
#define TRIG_PIN 3

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

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 < 5;
  digitalWrite(LED_BUILTIN, isNearby);
  lcd.setCursor(0,0);
  lcd.print("Distance=");
  lcd.setCursor(9,0);
  lcd.print(readDistanceCM());
  Serial.print("Measured distance: ");
  Serial.println(readDistanceCM());
  delay(100);
}