Crash of the IO_CPU


I have encountered a probleme with the refresh of the PWM output that leaded to a crash on our Dropix V2.1 unit.
After investigation we have found that the IO CPU that take care of sending the RC_OUT signal to the ESC is freezing, motor are stopping and drone is crashing.
I have opened an issue on ardupilot support board: PWM RC_Output no longer refresh and leads to crash
An other guy who is also using a Dropix got the same issue here: RC Inputs & Outputs freeze randomly (crashlog)
We are both using Ardupilot 3.4.5 version and a Dropix.
As the bug is not known by the developper team we would like to know if you have encountered the same kind of problem on some of the Dropix unit?
Do you have any idea how we can replicate this problem and try to solve this major issue?

Can you provide us the schematics of the power supply side and input/output ports of the IO_CPU to see if we can sense some signals?

If the IO_CPU resets, does it instantly come back to a normal operation or does it have to be initialized by the master CPU?

Thank you in advance,
Best regards,


Hello Cyril,

Thanks for the feedback, Ardupilot team contacted us about that as well. It is the first time this bug is encountered.

We have been looking at your logs as well and can tell there is a communication problem between IO processor and FMU processor indeed. It is however very difficult to find more because we haven’t been capable of reproducing the issue yet.

All the schematics are there :
There is no difference with original Pixhawk schematics on the microcontroller side.

Were you operating in a particular electromagnetic environment? Any element according to your scenario could help in debugging the problem so if you can please feel free to share that info.

We can keep this conversation in GitHub to avoid replicating topics if you prefer. You can ping me with @klopezal