Re: Real time USB2Serial devices and behaivor

Alan Stern
2008-03-27T02:58:49Z

On Wed, 26 Mar 2008, Greg KH wrote:

> > Is there any reason to think that if I created my own isochronous
> > USB2Serial adapter and iso-usb-driver that I couldn't get determinism?
>
> I strongly doubt it as others have tried and failed in the past.

I don't understand. Isochronous transfers have pretty strict
transfer-time guarantees. Why wouldn't this work?

One reason I can think of is that Iso transfers aren't reliable. But
then regular RS232-type serial transfers aren't reliable either.

The only other reason is that the USB stack itself has an unpredictable
amount of overhead. However I think it should fall within an
acceptable range for RT applications.

Alan Stern