On Thu, 18 Aug 2005, Pete Zaitcev wrote: > On Thu, 18 Aug 2005 21:52:25 +0000 (UTC), Uwe Bonnes <[EMAIL PROTECTED]> > wrote:
> > With every frame, I would like to send a USB command initiating a read of > > the interrupt status register of the SJA1000 and read the data send from the > > device with the read initiated in the frame before. Data is generally sent from a device in the same frame as the read that requested it. So saying you want to read the data sent in response to the request from the previous frame makes no sense. Maybe you meant that you want to act on the data sent for the request in the previous frame? But why do that? -- Why not act on the data as soon as you receive it, instead of waiting for a frame boundary? > > But data to the FT2232 is transferred via bulk endpoints. No interrupt > > endpoints are available with the FT2232. Sounds like a bad design to me. Or maybe the designers didn't anticipate anyone doing what you are trying to do. > Just queue two URBs and voila. It's not that simple. If you queue two bulk URBs, they will generally both execute in the same frame. To do what Uwe wants, it will be necessary to have a driver or program wake up every millisecond to submit a bulk URB. That can be done, although not reliably. And only if the computer has its timer interrupt rate set at 1000 Hz or higher (which isn't true of all platforms). On Thu, 18 Aug 2005, Uwe Bonnes wrote: > The low level layer has to decipher the data read from the interrupt status > register and only inform the upper levels if something interesting has > happened. That's how these things are normally handled. In this case, it would make the most sense if the device informed the computer only when something interesting had happened. That's how interrupt endpoints work. Alan Stern ------------------------------------------------------- SF.Net email is Sponsored by the Better Software Conference & EXPO September 19-22, 2005 * San Francisco, CA * Development Lifecycle Practices Agile & Plan-Driven Development * Managing Projects & Teams * Testing & QA Security * Process Improvement & Measurement * http://www.sqe.com/bsce5sf _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
