flyingpio_messages.h

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#define FPPROTO_MAX_SERVOS 16
#define FPPROTO_MAX_BANKS 4
#define FPPROTO_MAX_RCCHANS 10
#define FPPROTO_MAX_ADCCHANS 4

/* 34 bytes */

#define FLYINGPICMD_ACTUATOR 0xfc
#define FLYINGPICMD_CFG 0xfa
#define FLYINGPIRESP_IO 0x10

struct flyingpicmd_actuator_fc {
        /* fractional values; 0 = min, 0xffff = max */
        uint16_t values[FPPROTO_MAX_SERVOS];

        uint16_t led_status : 1;
        uint16_t flags_resv : 15;
} __attribute__((__packed__));

struct flyingpicmd_cfg_fa {
        /* This here is simpler than the controller-side configuration.
         * min is expected to be a true minimum; max is a true maximum.
         * The values that come in are scaled linearly between min and max
         * using fixed point math
         */
        struct {
                uint16_t min;   /* microseconds */
                uint16_t max;
        } actuators[FPPROTO_MAX_SERVOS];

        /* Rate in Hz;  0 is oneshot */
        uint16_t rate[FPPROTO_MAX_BANKS];
        uint16_t receiver_protocol;     /* If less than 0x100, this is from
                                         * HwShared.PortTypes
                                         */
        uint16_t flags_resv;    
} __attribute__((__packed__));

/* all IO data stuff must be equal/less than length of flyingpi_actuator_fc */
/* 20 + 8 + 2 + 2 = 32 bytes */
struct flyingpiresp_io_10 {
        uint16_t chan_data[FPPROTO_MAX_RCCHANS];
        uint16_t adc_data[FPPROTO_MAX_ADCCHANS];

        uint16_t valid_messages_recvd;
        uint16_t flags_resv;
} __attribute__((__packed__));

/* 3 bytes header */
struct flyingpi_msg {
        uint8_t crc8;
        uint8_t id;

        union {
                struct flyingpicmd_actuator_fc actuator_fc;
                struct flyingpicmd_cfg_fa cfg_fa;
                struct flyingpiresp_io_10 io_10;
        } body;
} __attribute__((__packed__));

static inline bool flyingpi_calc_crc(struct flyingpi_msg *msg, bool fill_in,
                int *total_len) {
        uint8_t len;

        switch (msg->id) {
                case FLYINGPICMD_ACTUATOR:
                        len = sizeof(msg->body.actuator_fc);
                        break;
                case FLYINGPICMD_CFG:
                        len = sizeof(msg->body.cfg_fa);
                        break;
                case FLYINGPIRESP_IO:
                        len = sizeof(msg->body.io_10);
                        break;
                default:
                        return false;
        }

        /* Fixup to include ID */
        uint8_t crc8 = PIOS_CRC_updateCRC(0, ((uint8_t *) &msg->body) - 1,
                        len+1);

        if (fill_in) {
                msg->crc8 = crc8;
        }

        if (total_len) {
                *total_len = len + 2;
        }

        return msg->crc8 == crc8;
}