/*
  Photoresistor (LDR) Analog Demo

  Copyright (C) 2021 Uri Shaked.

  https://wokwi.com/arduino/projects/305193627138654786
*/

#include <LiquidCrystal_I2C.h>

#define LDR_PIN A0
#define BUZZER_PIN 13

int BUZZER_FLAG = 0;

// LDR Characteristics
const float GAMMA = 0.7;
const float RL10 = 50;

LiquidCrystal_I2C lcd(0x27, 20, 4);

void setup() {
  pinMode(LDR_PIN, INPUT);

  lcd.init();
  lcd.backlight();
}

void loop() {
  pinMode(BUZZER_PIN, OUTPUT);

  int analogValue = analogRead(A0);
  float voltage = analogValue / 1024. * 5;
  float resistance = 2000 * voltage / (1 - voltage / 5);
  float lux = pow(RL10 * 1e3 * pow(10, GAMMA) / resistance, (1 / GAMMA));

  lcd.setCursor(2, 0);
  lcd.print("Room: ");
  if (lux > 50) {
    lcd.print("Light!");
    if (BUZZER_FLAG == 0) {
      beep();
      BUZZER_FLAG = 1;
    }
  } else {
    lcd.print("Dark  ");
    BUZZER_FLAG = 0;
  }

  lcd.setCursor(0, 1);
  lcd.print("Lux: ");
  lcd.print(lux);
  lcd.print("          ");

  delay(100);
}

void beep() {
  tone(BUZZER_PIN, 4000, 2000);
  delay(2000);
  noTone(BUZZER_PIN);
}