// Illuminance sensor (BH1750FVI) test

#include <LiquidCrystal_I2C.h>
#include <Wire.h>

LiquidCrystal_I2C lcd(0x27,16,2);
int BH1750 = 0x23;
byte buff[2];

void setup() {
  lcd.init(); 
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("COSMOLIGHT");
  lcd.setCursor(0, 1);
  lcd.print("Project Arduino");

  Wire.begin();

  // BH1750FVI reset
  Wire.beginTransmission(BH1750);
  Wire.write(0x07);
  Wire.endTransmission();
  
  // BH1750FVI mode set
  Wire.beginTransmission(BH1750);
  Wire.write(0x10);
  Wire.endTransmission();

  delay(3000);
}

void loop(){
  float dt = 0;
  float lxData = 0;
  int   i = 0;
  
  // BH1750FVI access start
  Wire.beginTransmission(BH1750);
  Wire.requestFrom(BH1750, 2);

  // byte read
  while (Wire.available()) {
    buff[i] = Wire.read();
    i++;
  }

  // access end
  Wire.endTransmission();

  dt = ((buff[0] << 8) | buff[1]);
  lxData = dt / 1.2;

  // data ---> LCD
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Illuminance(lx):");
  lcd.setCursor(0, 1);
  if (lxData < 0) {
    lcd.print("Data Overflow");
  } else {
    lcd.print(String(lxData, 1));
  }
  
  delay(1000);
}