Tim Roberts wrote:
> Wander Lairson Costa wrote:
>> I observed that benchmark firmware always expects isochronous transfer
>> of a size multiple of packet size. Is this just a convention on the
>> firmware or is there something about isochronous that I am missing
>> out?
> Isochronous requests are different from other requests. The "multiple
> of packet size" thing really only applies to isochronous IN requests.
> The reason is that isochronous data is not packed into your data
> buffer. Instead, each packet in your isoch request stands alone, and
> gets mapped directly to a single microframe in time. If your device has
> an interval of 1, so that you get a shot in each microframe, and you
> include 16 packets in your request, those 16 packets will span exactly
> two milliseconds. The first packet gets whatever is read in the first
> microframe, the second packet gets whatever is read in the second
> microframe, and so on.
I see now that you're doing a full-speed device, so you should modify
that paragraph to eliminate the mention of "microframes".
Instead, each packet in your isoch request stands alone, and gets
mapped directly
to a single frame in time. If your device has an interval of 1, so
that you get a shot
in each frame, and you include 16 packets in your request, those 16
packets will
span exactly 16 milliseconds.
etc.
--
Tim Roberts, t...@probo.com
Providenza & Boekelheide, Inc.
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