#include <Wire.h> //IIC
#include <math.h>

// Start measurement at 1lx resolution. Measurement time is approx 120ms.
#define BH1750_CONTINUOUS_HIGH_RES_MODE 0x10

// Start measurement at 0.5lx resolution. Measurement time is approx 120ms.
#define BH1750_CONTINUOUS_HIGH_RES_MODE_2 0x11

// Start measurement at 4lx resolution. Measurement time is approx 16ms.
#define BH1750_CONTINUOUS_LOW_RES_MODE 0x13

int BH1750address = 0x23;
byte buff[2];

void setup()
{
  Wire.begin();
  Serial.begin(9600);
}

void loop()
{
  int i;
  uint16_t val=0;
  BH1750_Init(BH1750address);
  delay(200);
  if(2==BH1750_Read(BH1750address))
  {
    val=((buff[0]<<8)|buff[1])/1.2;
    Serial.print(val,DEC);
    Serial.println("[lx]");
  }
  delay(150);
}

int BH1750_Read(int address) //
{
  int i=0;
  Wire.beginTransmission(address);
  Wire.requestFrom(address, 2);
  while(Wire.available()) //
  {
    buff[i] = Wire.read(); // receive one byte
    i++;
  }
  Wire.endTransmission();
  return i;
}

void BH1750_Init(int address)
{
  Wire.beginTransmission(address);
  Wire.write(BH1750_CONTINUOUS_HIGH_RES_MODE);// 1 lx resolution 120ms
  Wire.endTransmission();
}