SimpleBGC (alexmos) and APM

Hi all,

Aleksey has mentioned that he has an alexmos firmware update that supports MAVlink as a means of avoiding/eliminating sensor drift by leveraging flight controller attitude and GPS. 

Randy had mentioned "alexmos serial" support during the APM 3.3 beta period, but eventually transitioned to StoRM32, for which serial and later MAVlink integration was added. Is the serial support a mapping to the Serial 4/5 port on a Pixhawk, or something else (digital AUX pin)?

I happen to be a fan of alexmos, so I am hoping to connect the dots here, and I am happy to contribute pull requests, technology, or documentation (sometimes the most rare and valuable commodity) to help make it happen. I would like to be able to use "point camera here" region of interest in auto missions with an alexmos gimbal. Does anyone know if it is or was ever possible? Randy mentioned it was there but had not been tested, but it's not clear to me as an engineer how it's possible to implement something without any testing or verification whatsoever. Then that is the last indication I have found mentioning alexmos.

Why do I like alexmos? It was the first DIY-friendly controller to support encoders, and it happens to power my favorite gimbal (HD Air Studio InfinityMR). Not only that, I see Basecam continuing to expand their offerings with the new "extended" (CANbus IMU's!) and "pro" boards.

Can anyone give me the lay of the land for where we stand today? Then I will dig into the source to see if I can make sense of the state of things to figure out where we go from here.


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  • I'm in the process of ordering thew HDStudioMR Pro right now and have requested mavlink control to free up for slipring wires for other things. Have you got anywhere in achieving full mavlink communication with the alexmos controller?

  • hey Shawn! Maybe it's about time we get an effort together to sort it out. Do we have an idea how big the user base might be? It'd certainly be useful for us.

    Shawn McCracken said:

    Has there been any further development on this? 

  • Has there been any further development on this? 

  • Hi,

    Thank you for your post;

    I'm an Alexmos beginner and after a week working to avoid sensor yaw/azimuth drift by using SBGC Serial API 2nd Serial... :-(


    - Ardupilot ver. 3.3.3 rc2

    - Mission Planner ver. 1.3.35

    - Gimbal 3 axis iFlight G40

    - Gimbal Controller Alexmos 32bits

    - Board ver. 3.0 - Firmware ver. 2.56b9

    - SimpleBGC GUI ver. 2.56b7

    - Cable (3 wires: Tx, Rx, Grnd) connected on Pixhawk (Serial 4/5) <=> UART Gimbal Controller

    Mission Planner Parameter:

    - MNT_Type: 3

    - Serial4_ Protocol: 7

    - Serial4_Baud: 115

    SimpleBGC GUI setup

    - SBGC Serial API 2nd UART

    - Speed: 115000


    Miscommunication between SimpleBGC GUI and Gimbal Controller

    Roll, Pitch and Yaw is: Ok

    Any share or comment will be appreciate




    Capture Pic1.JPG

    Capture Pic2.JPG

    • that is interesting! Good to hear that the serial connection from Pixhawk is working for you. Are you able to use Mission Planner to point the camera, or are you using it specifically to counteract drift?

      I haven't seen that NullPointerException, but it looks like the serial connection is generally working. What specifically are you modifying when you see that error?

      It looks like that gimbal does not use encoders, is that right? I will try the 2nd UART as well; I hadn't tried that. I will need to figure out the pin mapping. Some of the mappings change when using encoders (my gimbal has them on all 3 axes).


      • My main purpose was to counteract azimuth drift for phtogrametry (Photoscan Pro)

        But unfortunately the only things tested so far are:

        - RC > Pixhawk: Roll/Pitch/Yaw via Serial SBGC  = OK

        - Follow Yaw = KO

        - In Mission Planner/Optional Hardware: No Type...?

        I'm Looking for any information at the moment about parameters to point the gimbal via Pixhawk Gyro

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