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Wire.beginTransmission(MAX_ADDR);
Wire.write(0x03); //here you request data from 0x03 (the Lux High-Byte Register)
Wire.endTransmission();

// You request two bytes of data (the register will only hold one byte)
Wire.requestFrom(MAX_ADDR, 2);
 
// and read this same byte into two variables 
if (Wire.available() == 2)
{
    	data[0] = Wire.read();
    	data[1] = Wire.read();
}

float MAX44009::get_lux(void)
{
	unsigned int data;
	
	Wire.beginTransmission(MAX_ADDR);
	Wire.write(0x03);
	Wire.endTransmission();
 
	// Request 1 byte of data
	Wire.requestFrom(MAX_ADDR, 1);
 
	// Read 1 byte of data
	if (Wire.available() == 1)
	{
    		data = Wire.read();
	}
 
	// Convert the data to lux
	int exponent = (data & 0xF0) >> 4;
	int mantissa = (data & 0x0F) << 4);
	
	float luminance = pow(2, exponent) * mantissa * 0.72;
  
	return luminance; 
}

float MAX44009::get_lux(void)
{
	unsigned int data[2];
	
	Wire.beginTransmission(MAX_ADDR);
	Wire.write(0x03); //request high-byte register data
	Wire.endTransmission();

	// Request 1 byte of data
	Wire.requestFrom(MAX_ADDR, 1);

	// Read first byte of data
	if (Wire.available() == 1)
	{
    		data[0] = Wire.read();
	}

        Wire.beginTransmission(MAX_ADDR);
	Wire.write(0x04); //request low-byte register data
	Wire.endTransmission();

	// Request 1 byte of data
	Wire.requestFrom(MAX_ADDR, 1);

	// Read second byte of data
	if (Wire.available() == 1)
	{
    		data[1] = Wire.read();
	}
 
	// Convert the data to lux
	int exponent = (data & 0xF0) >> 4;
	int mantissa = ((data[0] & 0x0F) << 4) | (data[1] & 0x0F);
	
	float luminance = pow(2, exponent) * mantissa * 0.045;
  
	return luminance; 
}