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?
Thats a great work-around, but not a solution. I'd be keen to understand whether this issue is caused by a hardware defect, or instead, is it the result of a code issue in arducopter? I'd be keen to know quickly if its a hardware issue so I can initiate a replacement whilst its still in warranty - with the hope that a modified version is available which doesn't inherit this issue. Can anyone please advise - hardware or software?
Most likely hardware. Somewhere in this thread there was a technical description of the causes of this problem.
And if I remember right there are no genuine 3DR Pixhawks showing this behavior (LSM303D reporting false values)
But I don't think you can get a guarantee that the replacement won´t show the same error.
Again, several posts up, I explained what exactly causing this issue- improper/low quality capacitor used by ****hawk manufacturers in the power line filtering of the LSM 303D. There is another abosolutelly different problem with some of the 3DR boards which is cause by the post production stress testing damaging solder joints of the MPU6k. 3DR played it nice and offers free board replacements. I had LSM303D failing midflight back in September, I just didn't know what was the reason for it back than.
I agree, 3DR does stand by their products and gives great support. Now my ***Hawk unit is working most every time I plug it in. I just adhered bubble level on it after a fitful 30 minutes of not arming after a long walk to my favorite flying field. I was using a horribly un-level picnic table. Eventually I placed it on a patch level patch of grass and it gave me a green light first try! I try to power it up perfectly level now. So far it works most every time. I will experiment different positions. Weird...
as Randy explained to me in 3.3 thread,its more important not to move your multi when pressing Arming button(aka safety switch) because Pix is doing accel calibration on batt power and again upon arming .....
but that wont help with your Bad accel health...Artem explained everything,THANK YOU ART,it helped me but you also teach me that I will buy only genuine 3DR.
Just to be clear, the gyro cal is done soon after the battery is attached and then again as part of the 1st arming. The LED should flash red and blue during these periods. It should be harmless to jiggle the copter while pushing the safety switch.
Ahaaaaa...sorry for spreading wrong information...
Banggood offered to replace my pixhawk clone (bizarrely with the same version I have already!). I see on their website however that they offer a newer version for sale, the v2.4.6 (mine is v2.4.5). This new version suggests, "product advantages:
-Improvencents on v2.4.5(added the second PMEG2005CT and 350ma ResettableFuse)"
Does this specific improvement address the power line filtering you mention? I.e. Does it address the accelerometer issue?
The link to product is here: New pixhawk
I had a 'bad compass health' message on the bench with 3.2 but the issue seemed to go away and I thought no more of it. Maiden over the weekend resulted in a yet to be explained crash - wonder if there is a connection?
Nothing to do with this issue but an issue nonetheless. Probably a bad compass :)
If you run 3.3 you can check this with the compass health DF message. My experience is that GCS messages that "disappear" are not truly gone but will re-emerge in flight but not be reported.
If your compass is not healthy it could just be a loose wire, worth checking before you start replacing stuff.
I haven't gotten a single ****hawk after this issues and how vendors handle it. Why bother if there is AUAV-X2. It is pin-to-pin compatible with pixhawk, it is literally half the size of the pixhawk and offers stellar build quality. Moreover it is designed and is manufactured in EU with local US sales rep. who I must say is very pleasant to deal with. To sweeten the deal it costs just $135 for a board with soldered pins+buzzer+safety switch. if you have a 3d printer you can print yourself several kinds of cases from readily available STL files, or pick one up at your favorite online 3D printing service for about $15-$20. Also, if you hate df13 connections, you'll be pleased to find out that AUAV-X2 uses standard servo pins! Manual does a great work explaining how to set it up properly.