No UDP packets transmitted after ARP reply

[Armageddon]

Hello,

I'm using the STM32F767ZITx MCU and the lwIP library to transmit and receive UDP packets every 1 ms.

Everything works fine but sometimes, after the ARP table has expired, UDP packets are no longer transmitted for several seconds even though my STM has received a response to its ARP request (as seen with Wireshark).

What solutions are there to avoid this scenario? Is this normal lwIP behavior?

Thanks for your help.

[Andrew Neil]

Have you enabled LwIP diagnostics, and/or added your own diagnostics, to see what's going on - in particular, what changes when this problem occurs?

https://community.st.com/t5/stm32-mcus-embedded-software/how-to-activate-debug-messages-for-lwip/m-p/234163/highlight/true#M15389

[Armageddon]

With my current system, I don't have a UART link available, I'm not on a proto board but a custom one.

What I'm seeing is that when I stop sending frames, the ARP table is empty, even though I'm receiving replies to ARP requests. It's as if it doesn't process replies.

[Andrew Neil]

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@Armageddon wrote:

With my current system, I don't have a UART link available

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That's a major oversight!

Can you use SWO instead?

Can you reproduce the problem on a board which does have suitable access?

[Armageddon]

You don't have all the ins and outs to tell me it's an oversight.
We have our constraints, and that's the way it's done. It would have been simpler to have it, but I'll do it with the classic probe debugging.

If I really can't do it, I'll consider moving my program to a proto to find a solution more easily.

I may have an idea, given that the system keeps receiving frames every 5ms, maybe the input buffers are saturated.

Thanks for your feedback, I'll keep you posted.