ardupilot/libraries/AP_Frsky_Telem/AP_Frsky_MAVlite_MAVliteToSPort.h

#pragma once

#include "AP_Frsky_MAVlite_Message.h"
#include "AP_Frsky_SPort.h"

#include <AP_HAL/utility/RingBuffer.h>

#include <stdint.h>

#if HAL_WITH_FRSKY_TELEM_BIDIRECTIONAL
/*
 * An instance of this class encodes a MAVlite message into several
 * SPort packets, and pushes them onto the supplied queue.
 *
 * process() will return false if there is insufficient room in the
 * queue for all SPort packets.
 *
 * See AP_Frsky_MAVlite.h for a description of the encoding of a
 * MAVlite message in SPort packets.
 */

class AP_Frsky_MAVlite_MAVliteToSPort {
public:

    // insert sport packets calculated from mavlite msg into queue
    bool process(ObjectBuffer_TS<AP_Frsky_SPort::sport_packet_t> &queue,
                 const AP_Frsky_MAVlite_Message &msg) WARN_IF_UNUSED;

private:

    enum class State : uint8_t {
        WANT_LEN,
        WANT_MSGID,
        WANT_PAYLOAD,
        WANT_CHECKSUM,
        DONE,
    };
    State state = State::WANT_LEN;

    void reset();

    void process_byte(uint8_t byte, ObjectBuffer_TS<AP_Frsky_SPort::sport_packet_t> &queue);

    AP_Frsky_SPort::sport_packet_t packet {};
    uint8_t packet_offs = 0;

    uint8_t next_seq = 0;
    uint8_t payload_count = 0;
    uint8_t payload_len;

    int16_t checksum;                       // sent at end of packet
    void update_checksum(const uint8_t c);
};
#endif