stm32c0 Spurious retransmission of USB IN packets

[cuwittrock]

Hi,

I have the stm32c071 and I am running with TinyUSB 18.0 on it using CDC profile. Seems to work nicely but perhaps one in a 1000 IN transmissions the endpoint is re-activated out of the blue. Can't see that TinyUSB is doing something to make this happen (unless I have overlooked something) so my question is whether anyone has seen this behavior? I am trying to find out if this is a SW or a HW issue, and since I haven't been able to spot anything in TinyUSB I am now reaching out to hear if anyone has some information/knowledge that could help find the root cause. At the moment I can get by by setting the COUNT_TX value to 0 in the endpoint register after each transmission. The endpoint ought to have remained in NAK state as no call has been made to initiate a new transmission, and since I don't like to go about changing code without having properly identified the cause I am hoping the someone can help me getting the bottom of this.

Kind regards,
Christian

[FBL]

Hi @cuwittrock 

TinyUSB is not supported by ST. To investigate the issue further, please use USBX or the ST library stack.

[cuwittrock]

Hi FBL,

I think that you missed the point. What I wrote in my post, is that I am seeing something that I suspect being HW related but I am not 100% sure so I am asking whether anyone has seen this issue INCLUDING the ST stack, or has some knowledge they can share. I am sorry, but it seems that you really did not fully read my post but only the first line.

Kind regards,
Christian

[FBL]

Hi @cuwittrock 

Setting COUNT_TX  to 0 after each transmission might be a useful temporary workaround while you investigate further. However, I'm not sure to understand the implications of this change and ensure it doesn't introduce other issues. To support you further, we need to reproduce using our stack.

EP unexpectedly re-activated is challenging to diagnose. Maybe attaching a USB trace can help as well.