PixRacer with Ardupilot

This is a discussion to focus the feedback and support of ardupilot on the PixRacer board from

We believe that all teething problems encountered are now resolved and so we recommend people load Copter-3.3.4 which is available for all multicopters through the Mission Planner's (and other GCS's) Install Firmware screens.  Note that because regular Pixhawks are still on Copter-3.3.3 the install icon may show Copter-3.3.3 but rest assured, Copter-3.3.4 will be installed (you can check the version by looking at the very top of the Mission Planner).


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    • When I do the live calibration like you say at the end it shows #1 and #2 even with just one checked.

      When I do the onboard I never get a beep or fitness value it just appears to continue to run with me moving it through all the axis like with the live.

      What am I possibly doing wrong . Help me out here Michael.

  • I am not understanding something here. Here is a test I tried. Disconnect your GPS, and see if you can calibrate your compass using the internal compass. I have tried this in every way I can think of and can not calibrate compasses unless it sees GPS/w external compass. Now I have seen several post by Chopper not being able to calibrate compass and now it is saying health problems with sensors. I don't have GPS/w compass on my machine as of yesterday and I am getting the same errors as chopper is. He has been told the problem sounds like hardware, I am beginning to believe it is software because I just duplicated his problem by removing the GPS/compass unit. Could we get some of the DEV's to remove the GPS/compass and see if it is possible to calibrate and if they can how do you do it. I am not trying to be smartass or sound disrespectful but just want to try to figure out what is going on and why is so much priority being given to the GPS when it should not be even used in some of the modes.

  • You got hit by the EKF bug.  Apparently EKF is always there and fuses the GPS into its readings even in Stabilize mode.

    Because you were not in the open, your GPS experienced sudden GPS drift in multiple directions.  EKF2 started to compensate by making big changes in roll and pitch.

    I don't like this as Stabilize used to be just simple and now its not.

    • isn't this suppose to avoid GPS ?

      EKF_GPS_TYPE: Controls how GPS is used.

      • 0 : use 3D velocity & 2D position from GPS
      • 1 : use 2D velocity & 2D position (GPS velocity does not contribute to altitude estimate)
      • 2: use 2D position
      • 3 : no GPS (will use optical flow only if available)
      Extended Kalman Filter (EKF) — Copter documentation
      • AHRS_EKF_USE : set to “1” to enable the EKF, “0” to disable and rely on DCM for attitude control, inertial nav (Copter-3.2.1)

        In Copter-3.3, this feature is forced to “1” and cannot be changed.


        I'm not sure that setting 3 will avoid EKF use without optical flow, it is unclear to me.

        Anyway , why AHRS_EKF_USE cannot be changed and is forced to "1" ?

        Extended Kalman Filter Navigation Overview and Tuning — Dev documentation
    • Agree and if I have well understand EKF has been a way to solve vibrations problem of  3DR Iris .

      I really do not see any advantage with EKF onlt problems and for what ?

      Vibrations are not a problem if you design a good frame and take care of motors and props balancing.

    • The last two auto missions I flew thank goodness I heard my Taranis tell me, "EKF variance... mode landing"!!! This is with 3.4 so I can't complain. Not sure if the same issue happens in 3.3 or what. External compass has low offsets... only using one gps. So not sure what more I could do. Don't really trust it now :[ This is with a 3dr Pixhawk not pixracer. 

      • I think this is not good at all.. 
        GPS cannot be trusted!  In my 2 years of flying now, GPS has given me more problems than anything else..  It's fine when flying 100 meters above everything, but as soon as I come down around trees or buildings to land or fly for fun, GPS is a complete mess..  drifts 20 meters any random direction at any moment... 
        I'd think GPS would be the very last thing the flight controller should consider in any mode... and it shouldn't even know it exists in manual modes!  (But Im not a developer and really don't know how EKF works, so maybe my opinion doesn't mean much....)

      • Yes, I believe 3.3 has it as well.  I think you can turn it off by setting AHRS_GPS_USE = 0.

  • Guys, I was flying today , was in althold all at once it yaw's left motors sounded like they went full and it hit the ground. GPS, was knocked off wires and plug ripped out of GPS and the buzzer was completely gone , I guess it ate it. When you look at the log it shows some errors but they were after it hit the ground.

    28 5-14-2016 7-23-40 PM.bin
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