Thanks I will look at the 2.0 spec. What would cause isochronous data to not arrive, or not arrive with good data?
So is there no way to guarantee data and timing with USB (1.1 or 2.0)? So syncing 2 USB busses is possible in Linux, but difficult as you explained. Can I use (micro)frame number? Are these numbers the same on two different root hubs? Ted Steve Calfee wrote: > At 10:38 AM 5/29/03 -0700, Ted Huntington wrote: > >Is syncronizing 2 isochronous signals possible on 2 different hubs? on > >the same hub? I need to make sure that data from 1 USB port and data > >from a different USB port arrive at my circuit at the same time (to > >within 1us). For now I am only using Full Speed. > > > >thanks > >Ted > > > >- > > You need to read the spec for usb 2.0 at www.usb.org But here are some > quick comments. > > USB is a serial bus, so if the devices are on the same bus (and full > speed), each bit is 84 ns, so your packet would have to be less than 12 > bytes (including overhead) to be less than 1us. Probably not possible or > useful. Might be possible at high speed. > > You might be able to use two root hubs, so you have two usb busses, but > then they will need to be somehow synchronized... possible but not easy. > > Iso is an unreliable send, so you are not guaranteed that both packets will > always arrive and arrive with good data. The only guarantee is bandwidth. > > Regards, Steve > > __________________________________________ > Steve Calfee -- embedded systems consultant > [EMAIL PROTECTED] > > ------------------------------------------------------- > This SF.net email is sponsored by: eBay > Get office equipment for less on eBay! > http://adfarm.mediaplex.com/ad/ck/711-11697-6916-5 > _______________________________________________ > [EMAIL PROTECTED] > To unsubscribe, use the last form field at: > https://lists.sourceforge.net/lists/listinfo/linux-usb-devel -- Ted Huntington Programmer Analyst I Main Library University of California, Irvine PO Box 19557 Irvine, CA 92623-9557 emesgs: [EMAIL PROTECTED] web page: http://business.lib.uci.edu/webpages/ted.htm 8:00a-12:00p Business Office (949) 824-8926 1:00p-5:00p Multimedia Resource Center (949) 824-1674 "Stop violence, teach science." ------------------------------------------------------- This SF.net email is sponsored by: eBay Get office equipment for less on eBay! http://adfarm.mediaplex.com/ad/ck/711-11697-6916-5 _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
