mavlink_command_sender.h

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/**
 * @file mavlink_command_sender.h
 * Mavlink commands sender with support for retransmission.
 *
 * @author Julian Oes <julian@oes.ch>
 */

#pragma once

#include <px4_platform_common/tasks.h>
#include <px4_platform_common/sem.h>
#include <drivers/drv_hrt.h>

#include <uORB/topics/vehicle_command.h>
#include <uORB/topics/vehicle_command_ack.h>

#include "timestamped_list.h"
#include "mavlink_bridge_header.h"
#include <v2.0/mavlink_types.h>

/**
 * @class MavlinkCommandSender
 */
class MavlinkCommandSender
{
public:
    /**
     * initialize: call this once on startup (this function is not thread-safe!)
     */
    static void initialize();

    static MavlinkCommandSender &instance();

    /**
     * Send a command on a channel and keep it in a queue for retransmission.
     * thread-safe
     * @return 0 on success, <0 otherwise
     */
    int handle_vehicle_command(const struct vehicle_command_s &command, mavlink_channel_t channel);

    /**
     * Check timeouts to verify if an commands need retransmission.
     * thread-safe
     */
    void check_timeout(mavlink_channel_t channel);

    /**
     * Handle mavlink command_ack.
     * thread-safe
     */
    void handle_mavlink_command_ack(const mavlink_command_ack_t &ack, uint8_t from_sysid, uint8_t from_compid,
                    uint8_t channel);

private:
    MavlinkCommandSender() = default;

    ~MavlinkCommandSender();

    static void lock()
    {
        do {} while (px4_sem_wait(&_lock) != 0);
    }

    static void unlock()
    {
        px4_sem_post(&_lock);
    }

    static MavlinkCommandSender *_instance;
    static px4_sem_t _lock;

    // There are MAVLINK_COMM_0 to MAVLINK_COMM_3, so it should be 4.
    static const unsigned MAX_MAVLINK_CHANNEL = 4;

    typedef struct {
        mavlink_command_long_t command = {};
        hrt_abstime timestamp_us = 0;
        hrt_abstime last_time_sent_us = 0;
        int8_t num_sent_per_channel[MAX_MAVLINK_CHANNEL] = {-1, -1, -1, -1}; // -1: channel did not request this command to be sent, -2: channel got an ack for this command
    } command_item_t;

    TimestampedList<command_item_t> _commands{3};

    bool _debug_enabled = false;
    static constexpr uint8_t RETRIES = 3;
    static constexpr uint64_t TIMEOUT_US = 500000;

    /* do not allow copying or assigning this class */
    MavlinkCommandSender(const MavlinkCommandSender &) = delete;
    MavlinkCommandSender operator=(const MavlinkCommandSender &) = delete;
};