In-flight Watchdog reboot on 4.0.4 and mro zero f7

Hi there,
yesterday we experienced an in-flight watchdog reset of the Flight Controller which caused a crash.
The Logfile after the reboot contained this Watchdog information

Does anyone have ideas what might have caused this ?
We are flying 4.0.4 and a mission controlled by a companion.
The crash happened after about 15 minutes of flying

@tridge do we have a bug here?

looks like we got a fault in the UART thread, the address is in this function:

ChibiOS::UARTDriver::write_pending_bytes_DMA(unsigned long)

the address matches this line of code:

now we just have to work out how we can generate a hard fault at that address.

hi @Daniel_Met, can you please tell me the exact UART setup you have. What devices are attached to what ports?
My guess from the log is you have a telem ratio on Telem1, you also have ESC telemetry enabled on SERIAL5. Was that active in the flight? I don’t see any ESC data logged.

Hi, thanks for looking into it.
You are correct, we have
Radio on 1, Companion on 2 and
Telemetry on serial 5
I added the logs here
The esc logs are present

do you have flow control pins to the companion?

No we don’t use hw flow control

@peterbarker and I are looking at this, but could you also see if you can reproduce on the ground? leave it running with companion active overnight. I’ve also setup the a mRoControlZeroF7 with the same params on my desk.

any guesses why the board voltage is varying like this?

period of over 20s

I will try to recreate it. We had several hours of flight time with two systems before this happened so it might take a while

I actually missed that when reviewing the log. Ill look into this

thanks, also check if the same VCC pattern is in earlier flight logs

The pattern is in earlier flight logs too.
It very likely comes from a onboard strobe light on the drone but i have to verify that

Hi we had a second Watchdog reset
i added the Logfiles to the Git Issue

@Daniel_Met I managed to reproduce the watchdog and I’ve proposed a fix here:

we plan on including this fix in the upcoming 4.0 point releases

@Daniel_Met I have built 4.0.5 with the DMA fix here:
this should fix the bug. If you have a chance to fly this and report back that would be appreciated!

1 Like

Thanks, i saw it earlier today we already installed it and will test

1 Like

Out of curiosity, was this issue present in earlier versions and on what hardware could this happen?
Im just curious why we didn’t have this issue before

the issue is most likely to happen when a UART TX DMA channel is shared with another high rate sensor. For the mRoControlZeroF7 the UART you are using at 921600 is shared with the SPI barometer.
Also note that I only managed to produce the bug once in my testing. I plan on trying some other approaches to making the bug happen more often later today.

1 Like

We did several testflights and so far the issue has not happened.
I think its prettly likely that the bug is fixed
We will continue to monitor it and if something happens again Ill report it.