gistfile1.txt

// Flags for the direction register
#define FLAG_M1_CCW 0
#define FLAG_M1_CW 1
#define FLAG_M2_CCW 2
#define FLAG_M2_CW 3

// Flags for the inopts register
#define FLAG_PULLUP_I1 0
#define FLAG_PULLUP_I2 1
#define FLAG_INVERT_I1 2
#define FLAG_INVERT_I2 3
#define FLAG_LIMIT_I1 4
#define FLAG_LIMIT_I2 5

// Flags for the int_masks register
#define IMASK_LIMIT_M1_I1 0
#define IMASK_LIMIT_M1_I2 1
#define IMASK_LIMIT_M2_I1 2
#define IMASK_LIMIT_M2_I2 3

// Flags for the status register
#define INPUT_M1_I1 0
#define INPUT_M1_I2 1
#define INPUT_M2_I1 2
#define INPUT_M2_I2 3
#define INT_1 4
#define INT_2 5

union {
    uint8_t bytes[1];
    struct {
        uint8_t slave_addr;
        uint8_t direction; // Motor direction register
        uint8_t speeds[2]; // Motor speeds, 0=off/idle, 255=full speed
        uint8_t inopts[2]; // Input options/flags registers
        uint8_t int_masks[2]; // Interrupt masks registers
        uint8_t status; // Input and interrupt status register
    } __attribute__((__packed__)) reg;
} registers;