Thomas Sailer wrote:
>
> Dan Streetman schrieb:
>
> > 2.Polling interval
> > The polling interval for bulk URBs is as-fast-as-possible. The device must
>
> I thought in case of a NAK the HC should wait for the next frame to try again,
> but maybe I'm wrong
>
Where do you read that or why do you think so? I think all HCDs send
more than
one request (also with NAK) to the devices (usb-ohci does it).
> > 3.Guaranteed polling
> > Interrupt URBs are (supposed to be) guaranteed to poll at certain intervals.
>
> Where is this guaranteed? If so our implementation is far away from this,
> think about eg. 65ms polling intervals
>
USB Spec. 1.1 chapter 5.7 (page 43)
- Guaranteed maximum service period for the pipe
The smallest polling interval is 1ms
(that's why there is a maximum of one NAK for a
int request during one frame).
So the real polling interval has to be between the maximum
service period (from EP descriptor)
and the minimum (1ms) period.
And our design goal should be to use a service period that is close
to the maximum service period for a pipe.
- Roman
> Tom
>
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