BH1750.h

/*

  This is a library for the BH1750FVI Digital Light Sensor breakout board.

  The BH1750 board uses I2C for communication. Two pins are required to
  interface to the device. Configuring the I2C bus is expected to be done
  in user code. The BH1750 library doesn't do this automatically.

  Datasheet:
  http://www.elechouse.com/elechouse/images/product/Digital%20light%20Sensor/bh1750fvi-e.pdf

  Written by Christopher Laws, March, 2013.

*/

#ifndef BH1750_h
#define BH1750_h

#if (ARDUINO >= 100)
#  include <Arduino.h>
#else
#  include <WProgram.h>
#endif

#include "Wire.h"

// Uncomment, to enable debug messages
// #define BH1750_DEBUG

// No active state
#define BH1750_POWER_DOWN 0x00

// Waiting for measurement command
#define BH1750_POWER_ON 0x01

// Reset data register value - not accepted in POWER_DOWN mode
#define BH1750_RESET 0x07

// Default MTreg value
#define BH1750_DEFAULT_MTREG 69
#define BH1750_MTREG_MIN 31
#define BH1750_MTREG_MAX 254

class BH1750 {

public:
  enum Mode {
    // same as Power Down
    UNCONFIGURED = 0,
    // Measurement at 1 lux resolution. Measurement time is approx 120ms.
    CONTINUOUS_HIGH_RES_MODE = 0x10,
    // Measurement at 0.5 lux resolution. Measurement time is approx 120ms.
    CONTINUOUS_HIGH_RES_MODE_2 = 0x11,
    // Measurement at 4 lux resolution. Measurement time is approx 16ms.
    CONTINUOUS_LOW_RES_MODE = 0x13,
    // Measurement at 1 lux resolution. Measurement time is approx 120ms.
    ONE_TIME_HIGH_RES_MODE = 0x20,
    // Measurement at 0.5 lux resolution. Measurement time is approx 120ms.
    ONE_TIME_HIGH_RES_MODE_2 = 0x21,
    // Measurement at 4 lux resolution. Measurement time is approx 16ms.
    ONE_TIME_LOW_RES_MODE = 0x23
  };

  BH1750(byte addr = 0x23);
  bool begin(Mode mode = CONTINUOUS_HIGH_RES_MODE, byte addr = 0x23,
             TwoWire* i2c = nullptr);
  bool configure(Mode mode);
  bool setMTreg(byte MTreg);
  bool measurementReady(bool maxWait = false);
  float readLightLevel();

private:
  byte BH1750_I2CADDR;
  byte BH1750_MTreg = (byte)BH1750_DEFAULT_MTREG;
  // Correction factor used to calculate lux. Typical value is 1.2 but can
  // range from 0.96 to 1.44. See the data sheet (p.2, Measurement Accuracy)
  // for more information.
  const float BH1750_CONV_FACTOR = 1.2;
  Mode BH1750_MODE = UNCONFIGURED;
  TwoWire* I2C;
  unsigned long lastReadTimestamp;
};

#endif