Bug in split transactions on Raspberry Pi
dianders at chromium.org
Tue Jan 26 09:07:47 PST 2016
On Tue, Jan 26, 2016 at 7:08 AM, Alan Stern <stern at rowland.harvard.edu> wrote:
> On Mon, 25 Jan 2016, Doug Anderson wrote:
>> 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?
> The Total Phase Beagle 480, with their Data Center analysis software.
Hrm. I've got the Beagle 5000 Superspeed on my desk. I can get it to
show me individual SOFs, but maybe that's a feature of the new
hardware? I'm using Data Center v6.63.000
I had to turn on lots of stuff to see all this and it eats up lots of
memory quickly, but it works. I've got:
Capture Settings, USB
-> Keep USB 2.0 Data-less Sequences
In device settings I make sure it's not Filtering anything...
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