#define TWI_SETSPEED 0x0401
#define TWI_GETSPEED 0x0402
#define TWI_SETSLAVEADDRESS 0x0403
#define TWI_GETSLAVEADDRESS 0x0404
#define TWI_SETSTATUS 0x0409
#define TWI_GETSTATUS 0x040a
#define TWERR_OK 0
#define TWERR_TIMEOUT 1
#define TWERR_BUS 2
#define TWERR_IF_LOCKED 3
#define TWERR_SLA_NACK 4
#define TWERR_DATA_NACK 5
#define TWSLA_MIN 17
#define TWSLA_MAX 79
#define TWSLA_BCAST 0
#define TWSLA_HOST 16
#define TWSLA_DEFAULT 193