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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Steven G

My oppologies if I was out of line in some way. Certainly the exchange of ideas and data here is what has helped the devs figure out what the issue is. Perhaps there is more yet to figure out. I was just trying to express my thoughts on the best way to help them out in that regard. Not that that was my place to say. In any event hope you get your intermittent problem figured out. 

You were not out of line. My point was simply I am not certain the root cause has been found. Maybe I just haven't seen all the facts and data. None the less, intelligent and polite discussion, including challenging hypotheses, makes for more robust problem solving. In the end, we all want to be confident in our hardware, as lord knows, human error is the biggest part of our challenge.

Yea I was a little out of line there. I should have read all the post in this thread before spouting off. I did think it was figured out. About the only constructive thing I can add is I had a few 'bad acc health' until I changed gps's. I haven't had any since. I don't have near the technical experience as many here to know what that means. And too bad I can't follow my own advice and produce a log :]

Which GPS were you using when getting the error, what did you replace it with, and did you also replace the wiring?


P.S. I looked through some logs from my 3DR Y6B last flown in August using AC3.1.5 and there were no errors for anything. The same Pixhawk is now on my new Y6 which does have errors (some not unrelated, but do recall an occasional "Bad Accel health" warning) but was never flown with AC3.1.5, only 3.2. Conclusion? Nothing.

The stock 3dr gps. Replaced it with both the NEO-7M had good luck [ no acc bad health anymore ] and more recently the M-8. I was never sure if it was the cable or the 3dr gps. The replacement gps's came with their own puck style cover and encased wires. 

I think I either damaged the 3dr gps or had bad wiring. But it took me a LONG time to figure out one of those two was an issue. Very intermittent... come to think of it. 

can someone comment on this videos


Steven, you and others are confusing when the Pixhawk reports problems with the setup vs reporting problems with the sensors.  The cause of the sensor failures is well understood. Issues that create problems with a specific vehicle setup are also understood and the autopilot is dutifully reporting a noisy position / attitude solution, but those issue are really up to the designer of that particular vehicle to resolve.  

Thanks for the input. Are you stating that the IMU failures have not been intermittent? When they fail, they fail hard and not soft? I guess I didn't understand it that way.
Further, by deduction, the failures or should I say warnings, that can be cleared by unplugging and plugging the battery are due to vehicle environment?
Are there trouble shooting guides? Or a fault tree logic diagram?
Is there another thread with more on trouble shooting? I don't to want side track this thread if there's anither more appropriate spot to discuss.

OK, in my attempt to gather more BIN / Log files from recent flights related to the this topic, I have since lost my SD card between taking it out of the Pix and getting it to my PC (DOH!)  Can someone point me to the right location to re-develop the files that need to be on the SD card so I can make a new one?  I can handle the firmware and parameters (settings) part.


Found it...  Definitely gonna make a copy now.

By the way, any blank SD card should work.  Ardupilot recreates the files and directories it needs.

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