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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          • If this works for me, i'll just use a spare battery connector and connect the poles. Just plug it in before fligt and voila. Not too difficult...
            • go ahead try, just make sure that you are experiencing the IMU2 failure i.e LSD303d, as far as I understand MPU6k issue should not be resolved this way. 

        • Very nice find!
          Looking forward to trying this in the field.
          I have some extra capacity in the lines to the ESCs so that fits in quite well.
          Did you actually measure the rate the voltage drops when battery is disconnected.
          • nope, my only instrument is a multimeter which I do not think is sensitive enough. 

  • What is the bottom line here? Is there a way to identify a faulty PIxhawk? I bought mine last June as a Y6B DIY.

    • MR60

      If when you turn your pixhawk on, it boots normally and does not display quasi systematically an unstable horizon and/or bad accel and/or bad gyro health, then your board is probably just fine. In my case, the bad pixhawk was obviously bad, giving strange HUD horizon instabilities and pre arm bad gyro health messages, almost at every boot.

      • I have one here that requires a compass calibration every time it boots up....

        • Developer


          Let's try and keep this thread focused on the accelerometer failures.  Could you report this separate issue in the APM Forum?  Including a log showing the problem would also be great.  Perhaps two dataflash logs, from two consecutive bots that show the failure.  Remember if it's happening before arming to set the LOG_BITMASK to log while disarmed.

        • I had something similar. The I2C was disturbed by the FRSky X8R Receiver ... No hardware problem..

  • can someone comment on this videos


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