> 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. Jeroen. _______________________________________________ Xenomai mailing list [email protected] http://www.xenomai.org/mailman/listinfo/xenomai
