On Wed, Mar 26, 2008 at 10:58:37PM -0400, Alan Stern wrote: > 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? I don't know, but the person who tried this a while ago said it wasn't really "real-time" enough for their application (robot arm movement). > 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. It's all about bounding the longest latency. Sometimes, under heavy loads, latency can be pretty big. But now that we have the -rt kernel, it might be a lot better than before, so that might be possible now, haven't tried it... good luck, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
