typedef enum
{
  TSL2591_GAIN_LOW                  = 0x00,    // low gain (1x)
  TSL2591_GAIN_MED                  = 0x10,    // medium gain (25x)
  TSL2591_GAIN_HIGH                 = 0x20,    // medium gain (428x)
  TSL2591_GAIN_MAX                  = 0x30,    // max gain (9876x)
}
tsl2591Gain_t;

typedef enum
{
  TSL2591_INTEGRATIONTIME_100MS     = 0x00,
  TSL2591_INTEGRATIONTIME_200MS     = 0x01,
  TSL2591_INTEGRATIONTIME_300MS     = 0x02,
  TSL2591_INTEGRATIONTIME_400MS     = 0x03,
  TSL2591_INTEGRATIONTIME_500MS     = 0x04,
  TSL2591_INTEGRATIONTIME_600MS     = 0x05,
}
tsl2591IntegrationTime_t;

#define TSL2591_COMMAND_BIT       (0xA0)    // bits 7 and 5 for 'command normal'

#define TSL2591_ENABLE_POWERON    (0x01)
#define TSL2591_ENABLE_POWEROFF   (0x00)
#define TSL2591_ENABLE_AEN        (0x02)
#define TSL2591_ENABLE_AIEN       (0x10)

enum
{
  TSL2591_REGISTER_ENABLE           = 0x00,
  TSL2591_REGISTER_CONTROL          = 0x01,
  TSL2591_REGISTER_THRESHHOLDL_LOW  = 0x02,
  TSL2591_REGISTER_THRESHHOLDL_HIGH = 0x03,
  TSL2591_REGISTER_THRESHHOLDH_LOW  = 0x04,
  TSL2591_REGISTER_THRESHHOLDH_HIGH = 0x05,
  TSL2591_REGISTER_INTERRUPT        = 0x06,
  TSL2591_REGISTER_CRC              = 0x08,
  TSL2591_REGISTER_ID               = 0x0A,
  TSL2591_REGISTER_CHAN0_LOW        = 0x14,
  TSL2591_REGISTER_CHAN0_HIGH       = 0x15,
  TSL2591_REGISTER_CHAN1_LOW        = 0x16,
  TSL2591_REGISTER_CHAN1_HIGH       = 0x17
};