On 2014-11-03 18:14, Gilles Chanteperdrix wrote: > On Mon, Nov 03, 2014 at 06:12:11PM +0100, Jan Kiszka wrote: >> On 2014-11-03 09:03, Jeroen Van den Keybus wrote: >>>> I try to write a hard real time usb driver. I communicate my device using >>>> open(), read() etc. My device is a gpio module. >>> >>> >>> I assume you want to control an USB host controller using a GPIO interface ? >>> >>> >>>> I am coding a kernel module >>>> to communicate the device using xenomai on real time. But I am not sure >>>> that this way is reasonable. If I should going on this way, what should I >>>> implement? Could you give me some example or link to write hard real time >>>> usb driver for* physical* device? >>> >>> >>> I cannot help you with that, but one important issue to consider is that >>> the USB protocol itself operates with small, hardware controlled time slots >>> of 1 ms (USB1.x) or 125 usec (USB2.0). You may therefore need a significant >>> amount of software to properly distribute real-time traffic in these - >>> essentially asynchronous - slots. The latency of a real-time process >>> waiting for USB data can therefore also be as large as the time slot >>> duration. If your real-time requirements are modest, you may be able to >>> live with that. Still, count on a major software effort: just have a look >>> at the Linux USB driver framework. >>> >>> Alternatively, you could check if you can synchronize your real-time >>> process with the USB controller frame rate. >>> >> >> FWIW, we still don't have USB 2.0 support (though I vaguely remember >> previous efforts in that direction), > > There is one here: > http://sourceforge.net/projects/usb20rt.berlios/ > > Have not looked at the code though.
Yeah, that's the one I recalled. Seems dead, unfortunately. Jan -- Siemens AG, Corporate Technology, CT RTC ITP SES-DE Corporate Competence Center Embedded Linux _______________________________________________ Xenomai mailing list [email protected] http://www.xenomai.org/mailman/listinfo/xenomai
