How to add a custom mavlink messages and send it to the qgroundcontrol?

1

From https://pixhawk.org/dev/mavlink_and_uorb_custom_message?, I can see that the new class is defined as follows
class MavlinkStreamCaTrajectory : public MavlinkStream
{
public:
MavlinkStreamCaTrajectory() : MavlinkStream() { }
const char *get_name() { return “CA_TRAJECTORY”; } // this will be the name of the stream
MavlinkStream *new_instance() { return new MavlinkStreamCaTrajectory(); }

private:
MavlinkOrbSubscription *_sub;
struct ca_traj_struct_s *_msg;

protected:
void subscribe(Mavlink *mavlink)
{
_sub = mavlink->add_orb_subscription(ORB_ID(ca_trajectory_msg)); // make sure you enter the name of your uorb topic here
_msg = (struct ca_traj_struct_s *)_sub->get_data();
}

    void send(const hrt_abstime t)
    {
            if (_sub->update(t)) {
              mavlink_msg_ca_trajectory_send(_channel,
                                             _msg->timestamp,
                                             _msg->time_start_usec,
                                             _msg->time_stop_usec,
                                             _msg->coefficients,
                                             _msg->seq_id);
          }
    }

};
while from the mavlink_messages.cpp file , I can see the new class is defined as these
class MavlinkStreamAttitude : public MavlinkStream
{
public:
const char *get_name() const
{
return MavlinkStreamAttitude::get_name_static();
}

static const char *get_name_static()
{
    return "ATTITUDE";
}

uint8_t get_id()
{
    return MAVLINK_MSG_ID_ATTITUDE;
}

static MavlinkStream *new_instance(Mavlink *mavlink)
{
    return new MavlinkStreamAttitude(mavlink);
}

unsigned get_size()
{
    return MAVLINK_MSG_ID_ATTITUDE_LEN + MAVLINK_NUM_NON_PAYLOAD_BYTES;
}

private:
MavlinkOrbSubscription *_att_sub;
uint64_t _att_time;

/* do not allow top copying

The format is so different, and I did what the tutorial said, and there occured a problem,
no matching function for call to ‘MavlinkStream::MavlinkStream()’
MavlinkStreamPMENV() : MavlinkStream() { }
Could anybody give me some advice?

2

The compiler told you what the problem is. It cannot find the function MavlinkStream::MavlinkStream() because it does not exist.

MavlinkStream *new_instance() { return new MavlinkStreamCaTrajectory(); }

Probably this is your error, you have to pass the function a pointer to the parent mavlink instance.