Read only specific autopilot values like compass heading with pymavlink

Ground Control Software MAVLink
1

Hi, I am currently using pymavlink on a Raspberry Pi and all is going well.

I am requesting the current compass heading or the lat/lon using the
“msg = vehicle.recv_match(type=b’VFR_HUD’, blocking=True, timeout = 2 ) command.

It works well, but it seems to be wasting time, since the autopilot is sending out allot of data that I do not need. Can I request only one current status value like “VFR_HUD” or only the current compass heading?
If I continuously loop and read the compass heading, then it takes between 200-250ms. I do understand that I can increase the update time.
Thanks for any suggestions.

2

Yes, you can request only the mavlink messages you want at the intervals that you want.

google for “request_message_interval mavlink” it will get you:

https://ardupilot.org/dev/docs/mavlink-requesting-data.html

3

I just figured it out. Posting the code here:

while True:
    vehicle.mav.command_long_send(vehicle.target_system, vehicle.target_component, mavutil.mavlink.MAV_CMD_REQUEST_MESSAGE,
                          0,  # confirmation - always 0
                          74,  # mode_id  VFR_HUD=74  GPS=33
                          0,  # Param 2
                          0,  # Param 3
                          0,  # Param 4
                          0,  # Param 5
                          0,  # Param 6
                          0)  # Param 7

    ack_msg = vehicle.recv_match(type='COMMAND_ACK', blocking=True, timeout=3)
    #### COMMAND_ACK has a message id of 512.

    msg = vehicle.recv_match(blocking=True)

    if msg.name == 'VFR_HUD':
        print (msg.heading)
    elif msg.name == 'HEARTBEAT':
        print (msg)
4

Not request message.
Request message interval.