Issue with MT7612U

[InanixFR]

Hello,

For several drones we use MT7612U without any issue.
But for one of them, we get this errors in the dmesg :

mt76x2u 1-1:1.0: tx urb failed: -71
And the WFB-ng is disconnected to the ground station
This appears when we arm the drone with the propellers mounted. Before that the communication if fine.
If we arm without the propellers mounted, we don't have this disconnexion. But if we push the throttle, the error appears.

We suspect a voltage drop, but the RPi didn't seems to be disturbed by it (no low voltage message)

This is the log WFB-ng file
wfb-ng.log

Do you have any idea to debug this issue ?

Before this we also have a lot of the following messages in the dmesg :

net_ratelimit: 102 callbacks suppressed
af_packet: wlx387acc8480b2 selects TX queue 2, but real number of TX queues is 1

But we have also those messages on other drones that don't have the disconnexion issue.

Thanks

[svpcom]

Do you have something like usb device disconnected or EMI ... in dmesg ?

[svpcom]

If yes, then it may be some EMI issue and you need to use shielded usb cable

[InanixFR]

No, I don't have any of this messages.

I made some other tests and I found new messages in dmesg :

[ 2907.461608] mt76x2u 1-1:1.0: MAC error detected
[ 2907.503713] mt76x2u 1-1:1.0: tx urb failed: -71
[ 2907.503828] mt76x2u 1-1:1.0: tx urb failed: -71
[ 2907.641524] mt76x2u 1-1:1.0: MAC stop failed

If I do a usbreset and restart WFB-ng, every thing is UP and then I meet again the deconnexion.

We are not really able to use shielded cable :

We have a full electronic stack that integrate Flight Controller, ESC, Rpi CM4 and the wifi card in a compact way.
On the electronic boards, the USB differential pairs are OK.

We also tried with a capacitor on Wifi card power pins, and also by disconnecting cameras

[svpcom]

Try to set

[base]
use_qdisc = True

[InanixFR]

With QDISC enabled i don't have anymore those messages

net_ratelimit: 102 callbacks suppressed
af_packet: wlx387acc8480b2 selects TX queue 2, but real number of TX queues is 1

neither

mt76x2u 1-1:1.0: MAC error detected
mt76x2u 1-1:1.0: MAC stop failed

But I still have
mt76x2u 1-1:1.0: tx urb failed: -71
And WFB-ng doestn't send any messages.

Note that WFB-ng is still alive in the processes.

[InanixFR]

The strange behavior is we use this stack on other drones without this issue.

The only differences are the motors (little bit bigger) and the battery (4S VS 2S).

[svpcom]

This may be EMI interference from the motors via power line. What DC/DC do you use for power RPI + wifi card?

[InanixFR]

Bad news...

We use 2 chips LMR51450SDRRR :

• one for 3V3 (wifi card)
• one for 5V (RPi)

https://www.ti.com/product/LMR51450/part-details/LMR51450SDRRR?utm_source=google&utm_medium=cpc&utm_campaign=app-null-null-app_opn_en-cpc-storeic-google-eu_en_pur&utm_content=Device&ds_k=LMR51450SDRRR&DCM=yes&gclsrc=aw.ds&gad_source=1&gad_campaignid=18945642618&gbraid=0AAAAAC068F0TBeZXFP3ZHB52Q22NOf5GR&gclid=CjwKCAjwiY_GBhBEEiwAFaghvrBLgEbkeLk_MT_Zomt6ZRAOorNHR1YiH6qMjXQCgBm3RcI26LNy_hoCPtoQAvD_BwE

Thanks a lot for yoru help