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Overriding Remote Control from a custom GS with MAVLink

Posted by Valentin Brossard on February 24, 2014 at 1:38pm

Hello,

I am trying to create a custom ground station that could take off the Quadcopter when a camera detects a predefined target. Basically, there are a camera, a computer and a Quadcopter. The computer sends MAVLink commands to the APM3.1 and no remote control shall be used.

I am running a C++ program that arms the Quadcopter with MAVLink but I can't manage to make it fly.

I first tried to override remote control with RC_CHANNELS_OVERRIDE MAVLink command but the Quadcopter does not answered to my request. I then tried with MAVLink missions. I succeed in sending mission to the Quadcopter (I can see them with Mission Planner) but when I switch to AUTO mode, nothing happened.

I'm probably missing something but I've been looking around for a while and I didn't manage to find anything. If you've done that kind of things and if you've got some time to spend for a newbie, any help would be warmly welcomed.

Thanks.

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Tags: apm, c++, ground, station, code, override, quadcopter, source
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Replies

  • Alexander March 14, 2014 at 10:40pm

    Hi Valentin, can give some advices on this rc overriding issue? I'm facing the same problem here..... when using RC_CHANNELS_OVERRIDE command in Mavproxy, the quadcopter seems to have no response at all.....i'm using the command " RC all 1000" just to override all the channels in case of emergency thru mavproxy....but somehow it seems to have no effect at all. Appreciate your help thanks. Need it urgently for my final year project T.T

    • Valentin Brossard > Alexander March 17, 2014 at 1:08am

      Hello Alexander,

      Actually, I am not using MAVProxy to override RC Channels. I am using a dedicated cpp program.

      Sorry but I can't help you :-(

      • Dries Hulens > Valentin Brossard February 24, 2015 at 3:41am

        Hi Valentin,

        I'm also trying to override rc channels from in a C++ program. I tried with mavproxy and that works, so the firmware in my hexacopter (pixhawk) is receiving the commands, also with Mission Planner I see the values of the RC move...

        Now i am trying from in my C++ program. The arming works fine, as i can see also in mission planner, but the RC_CHANNELS_OVERRIDE wont work.

        This is the code that runs in a loop every 20ms:

        mavlink_rc_channels_override_t rc_override;///Msg to override rc channels
                mavlink_message_t msg_rc;
                rc_override.chan1_raw=1100;
                rc_override.chan2_raw=1100;
                rc_override.chan3_raw=1100;//Lowest throttle
                rc_override.chan4_raw=1100;
                rc_override.chan5_raw=1100;
                rc_override.chan6_raw=1100;
                rc_override.chan7_raw=1100;
                rc_override.chan8_raw=1300;
                rc_override.target_system = 1; // Send command to MAV 001
                rc_override.target_component = PX_COMP_ID_ALL;
                mavlink_msg_rc_channels_override_encode(systemID, 0, &msg_rc, &rc_override);
                sendMAVLinkMessage(lcm, &msg_rc);

        systemID = 255.

        Did you put your controller in a special mode ? or do you also have to send a heartbeat message every ... seconds ?

        IS it possible to send me a example where you send your RC override commands ?

        Kind regards,

        Dries

        • Alexander Trujillo > Dries Hulens February 24, 2015 at 4:07am

          Hello Dries,

          I think I can help you with your problem. I managed to run a program in C similar to yours and I found a lot of problems to do it due to the lack of information about MAVLink.

          In my investigation I concluded that you need two things to make it works. First of all, you need the correct system ID which is saved onto the APM or PIXHAWK. So, with Mission Planner software you can check this to be sure you are using the correct ID. Here you have a picture example:

          3702779322?profile=originalThe second thing you have to do is to send a HearBeat message every second or two seconds, if possible. This may inform UAV that you are still there and have not lost the communication. This last step is very important because the Ardupilot have a dedicated Failsafe that checks the communication between the UAV and the GCS if the RC_OVERRIDE command is working.

          I hope this information can help you.

          Kind regards,

          Alexander.

      • Alexander > Valentin Brossard March 17, 2014 at 5:47am

        i see :( ......Being posting this in many forums but didn't get positive feedback on this issue. I wonder which part goes wrong coz everyone seems to have no problem with the one im having now....actually it's just to override the rc channel but dunno why my quadcopter doesn't respond to it. Thanks for your reply anyway, really appreciate it :)

  • Valentin Brossard February 25, 2014 at 2:36am

    Hello,

    I finally managed to use the RC_CHANNELS_OVERRIDE MAVLink command. (I'm ashamed to say that I used a wrong GCS System Id...)

    By the way, I am still interessted in knowing why I can't make the motors spin with missions.

    • mohsein > Valentin Brossard November 24, 2014 at 3:43am

      Hello dear Valentin Brossard

      I am also working on commanding APM through matlab.

      I am actually new on it and i need some one to help me.

      as you have done projects like it, I want to ask you for help if it is possible for you.

      this is my email adress mfzavareh@hotmail.com

      any help on this subject would be appreciated

      thank you so much

    • Lucas Behnck > Valentin Brossard April 11, 2014 at 11:35am

      Hello Valentin,

      I am sorry for resurrecting your post but I am afraid I need your help. I am trying to control a quadcopter through a C program using mavlink. I am able to arm the quad using command_long, but it does not responds to any other commands (like for instance rc_override or set_mav_mode).

      Besides using the arm command, did you do anything different before flying? I mean, what did you use as GCS system id in your program? Did you use CHANGE_OPERATOR_CONTROL function? I just can't see what I am doing wrong.

      Thank you in advance for your help!

      • mohsein > Lucas Behnck November 24, 2014 at 11:18pm

        Hello dear Lucase Behnck

        I also want to control the quadrotor with Matlab

        I use a mexFunction for that

        I want to know the code you have used to arm the APM because I can not arm it. i can have the attitude in Matlab but I can not arm it.

        your help will be appreciated.

        my email is mfzavareh@hotmail.com

        thank you so much

        setupSerial.m

        MavSerial1.mexw64

        https://storage.ning.com/topology/rest/1.0/file/get/3701883768?profile=original
      • Valentin Brossard > Lucas Behnck April 14, 2014 at 12:26am

        Hello Lucas,

        Here is the sequence I use do override remote control :

        -> Heartbeat - To introduce myself as a ground station ;

        -> Arm Command

        -> Wait a few seconds

        -> Override RC Commands

        As a Ground station, I use the sys_id 253.

        I hope it will help !

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