Bug in split transactions on Raspberry Pi

[Alan Stern]

On Mon, 25 Jan 2016, Doug Anderson wrote:

> Hi,
> 
> 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.

Alan Stern