Pixhawk BAD ACCEL HEALTH APM 3.2 - collecting data

A few users, myself included, appear to be having issues calibrating accels and/or arming when using APM 3.2 on a Pixhawk.  I see posts here and there, but thought it may be best if those having the issue could all 'check in' to one post so that the developers can see how widespread the issue is and gather data.

My Pixhawk will arm occasionally, and will even fly successfully.  Occasionally however it will not arm and I will receive the pre-arm error "Accels not healthy".  A few days ago I was able to arm and fly thorugh one lipo, then after landing and swapping batteries I could not arm due to this reason.  I have attached the logs from the successful flight, as well as the failed pre-arm logs, to this post.

As you can see from these images there is something amiss with IMU2.  This is a snippit from the good flight, showing values for AccX on IMU1 and IMU2:


and here are the same values on the second attempt, pre-arm.


In the 3.2 release thread a few users had mentioned the issue and Randy advised to set the log_bitmask to "131070" so that it will log everything including the pre-arm checks.  I encourage others having the issue to do the same and share the logs and experiences here so that we can find out what is going on here - is there a bad batch of Pixhawks in the wild that only now show the hardware errors due to something new in 3.2, or is there an issue in the APM software?



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    • yep, it never has acc problems when powered through USB or when USB is connected even if the main lipo is plugged in. Also, I can say that putting a 5.4v BEC on the RCIN input (basically plugging an extra BEC for servos/retracts into the RX with power wire connected to the Pixhawk) will NEVER pass the acc precheck. As soon as I unplugged the power wire from the Rx-pixhawk cable I had issue only once in a cold environment. Also, it seems that changing MPU6k filter frequency will contribute to this issue. 

      EDIT: I will try powering pixhawk with  5v and a bit less and see if the problem could be somewhere in the Pixhawks internal voltage regulation (as APM's 3.3v reg)

  • I have been facing a similar problem. But in mine it says 'Bad Gyro Health'. I am sure I have done all the steps properly but it is never passing the PreArm Checks. Also the it is taking time to get a 3D GPS Fix. There are GPS problems in the part of the world I live, but 4 sats? That was never the case.

    Please throw some light on this issue. Logs attached!

    2015-01-04 16-12-36.tlog

    • I also am have problems flying in the cold weather here in nebraska. Same mystery error. Also I notice my compas is calibrating with two conflicting values
  • Hi, I have recently had an interesting mid-flight failure with AC3.2 and Pixhawk.

    Basically closer to the end of the flight both IMUs Z axis went mayhem while X and Y remained sane. Not sure if this is related, but would would appreciate Mr. Tridgell taking a look at it just to determine if it could be related, as right before the flight I had experienced bad_accel issue, it took me about 3-4 power cycles to pass the checks. Anyways, issue is more thoroughly explained here: http://diydrones.com/xn/detail/705844:Comment:1869597

    Thank you. 

  • I wonder if this is anything like this issue I experienced with my old APM 2.5:



    • Fast temperature changes is something what sensors don't like - for example baro can show you big alt changes (even with correct code for temp compensation). This is reason why I am trying to power board and then let it for a while to heat itself to some stable temperature,

      But this could be point - internal generated heat can be jump in temperature of sensor what will make problem to pre arm check. If I put BT module on, it generates heat faster and so it make problems more often. Or when someone take copter from heated car and try to arm, it can change temperature in opposite way,

      What about some kind of "temperature change" check during initialization ? 

  • I found very similar problem - problem with Accel health in low temp (1-5 degree celsius). I didn't downloaded logs (not sure if I have there all prearm logs) yet but I have one idea

    Is it possible that bluetooth module attached to Serial1 makes problem ? I disconnected it and then it start work without problem (2 flights in same temp). Before, I did maybe 5x restarts and nothing. 

    HW is HKPilot32

  • Hello,

    same issue :-(   bad accel health,wont arm

    weather 3°C, imu2 (~ -8g constant on XYZ)

    HW: Dropix ,French made pixhawk

    after several reboot (5/6) i managed to fly.

    one days before, normal init in my garage (T°?), and cool poshold flight in 20/50 km/h of wind.

    makes more test for the T° today,   max 2°C outside, 17/18° expected inside.

    I hope that some else in the tropic have the same issue...

    volunteer for tests ;-)

    2014-12-29 16-54-33.bin

    • Developer

      Hi Vic,

      Can you please do some testing with this firmware:


      That version includes an attempt to fix the issue you are seeing. I don't have direct access to a board that has this problem, so a DF log would be much appreciated.

      Cheers, Tridge

      • Hi Andrew!

        i'd haven't see your post before mine.(family Christmas holidays, several things in same time ;-) )

        Just restart my drone,in my workshop (18°! yes!! ): ok.

        Put it outside, without woolly hat, just to see...waiting

        flying session with friend is planning this afternoon, if i have same issue, i hope, I'll flash the FW and make a return here.

        I'm afraid to miss-understand DF logs?


This reply was deleted.


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