Bug in split transactions on Raspberry Pi

Doug Anderson dianders at chromium.org
Mon Jan 25 14:02:23 PST 2016


On Mon, Jan 25, 2016 at 1:51 PM, Alan Stern <stern at rowland.harvard.edu> wrote:
> On Mon, 25 Jan 2016, Peter Stuge wrote:
>> Alan Stern wrote:
>> > the device's embedded hub ACKs the packets from the PC and not the
>> > packets from the RPi.
>> >
>> > What other differences could there be?  Timing?  Power levels?
>> Yes, both good candidates. Can you measure VUSB?
> Distinctly higher than 5V.
>> As for timing, the
>> host controller will send SOF more or less regularly, if too
>> irregular then that could cause problems for the device. Does your
>> analyzer provide precise timestamps?
> Yes, but the software doesn't want to display individual SOF packets.
> However I can see, for example, that 84 SOF packets were sent during a
> 10.3-ms period.  Or 2048 were sent during a 256-ms period.  It seems
> pretty regular.

What analyzer are you using?


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