[TriEmbed] USB RNDIS enumeration help needed

[Trampas Stern]

I figured out that my driver was not sending a zero length packet after
receiving the RNDIS Initialize message.  This fixed the problem above, and
now I am on to debugging the next issue.

Thanks
Trampas

On Thu, Feb 27, 2025 at 9:50 AM Trampas Stern <trampas at gmail.com> wrote:

> I am trying to do USB RNDIS enumeration and having issues.  I have googled
> and read everything I can find and keep running into issues.   I get the
> enumeration working and it will work for days on my PC, then at some point
> it will not work.   I switch hubs, ports and it might work again for days,
> then stop.
>
> I have been using Saleae logic analyzer as well as USB protocol analyzer
> (Total Phase Beagle device) and have been unable to figure out the issues.
>
>
> My initial thoughts were that Microsoft was doing some
> predictive analysis on device timing.  That is, I noticed that if the USB
> request from the host came in too quickly it would cause issues.   I
> figured that based on the packet NAKs that Microsoft might dynamically
> change request timing to compensate for slower devices.  I figure this
> would maximize the bus bandwidth utilization by not sending packets that
> most likely would be NAK'd.  I am not sure if this is true or not, but
> sounded reasonable?   I since changed my device to be all interrupt driven
> for fastest response.  This addressed some issues, but not all of my
> problems.
>
> Now I seem to have hit another issue.  The host sends an RNDIS Initialize
> message, after which I setup device's USB peripheral to send the
> RESPONSE_AVAILABLE message, however the host never seems to poll for the
> RESPONSE_AVAILABLE  and then timeout on the RNDIS Initialize message.
>
> I have previously seen this behavior and found that if I delayed setting
> up the RESPONSE_AVAILABLE message it would sometimes work.  Specifically, I
> would send the REPONSE_AVAILABLE using main loop verses right away in the
> interrupt handler and it would work most of the time.  This did not make
> any sense as that as I understand it the host has to poll for the
> RESPONSE_AVAILABLE so the timing of configuring peripheral to send message
> should not matter, since it is all host driven system.  As I understand it
> the host does an interrupt polling messages to the RNDIS command end point
> to request the RESPONSE_AVAILABLE.  I am not seeing and polling message
> from host (Windows) on the RNDIS interrupt end point.  I do see EP0
> polling, but not ones on the RNDIS command endpoint.
>
> I was wondering if anyone had experience with USB and  possibly could
> offer some advice, education, or help.  I do have all kinds of data
> captures and logs etc..
>
> Thanks!
> Trampas
>
>
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