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?
Replies
Would be nice if you people state from where you get your board...no one will punish you if its not original..
Quite awesome. Good stuff!
In the mean time..... for people with LSD303d failure ie IMU2 (wont work with mpu6k issue).
When experiencing the failure i.e. "bad_acc_health" try unplugging the battery and shortening PM battery input pins for 5-10 secs. Worked every-time for the last 30-40 times, make sure you unplug ALL your batteries from your system beforehand.
It works! Thanks
Just curious, what led you to this approach?
Multiple things.... but the final tip was googling "issues with lsm303d" first hit is pololu community forum thread. Apparently lsm303d is very sensitive to how it needs to be powered down: if voltage goes to 0 right away all is good, but if it falls at a certain rate lsm303d gets stuck on a single value until voltage drops to 0. Also the new 2.4.6 version of the ****hawks with "original NEC tantalum capacitor" to stabilize sensors. I figured out that the issue was with the power, originally I though of bad filtering so I put an LC filter on one of the machines and that "cured" my issue as well, now I understand why - the additional capacitors were changing the way power was dropping.
P.S. someone of pololu staff mentioned adding a 1k-10k resistor across LSM303D vdd to guarantee instantaneous voltage drop, but I haven't tried that myslef as I am not sure what will be the result of adding a resistor between 5v and ground on the pixhawk, if someone knows its safe/unsafe let me know.
Well, thanks for letting us know. I really expected that it will be something with power because it went away when I take off bluetooth module from copter. I can imagine that this will simply change way how is voltage getting off.
Can you give us your LC circuit schematic ?
Lol, that is a simplest diy LC filter: a torroid with a 470uf cap I ususally use them on my fpv gear. I really think that's just the cap that makes the difference. Also, I figured out that it is much easier, "cleaner" and safer (some setups have 2+ batteries which one might forget to unplug befor the short) to put 4.7k resistor right on the PM 5v vdd on the reverse side of the PM module. But can't stress enough this will work ONLY for IMU2 failure. Also, this is a workaround, the cloners used cheap alternative capacitor which is most liekly will be posible to replace, however I do not know which one.
This is a fantastic find!! It explains my issues much better than the "micro-fractured" solder joints. This is along the lines that I suggested in an earlier post. Great detective work.
Since "shorting" the Vcc connection (without power) before every flight is a PITA, a RC fix would certainly be best.
Thanks!!
-
10
-
11
-
12
-
13
-
14
of 46 Next