[Wince7] USB device driver RRS feed

  • Question

  • I have a USB device (USB2.0),but I always get the value of 64 at wMaxPacketSiz field of the endpoint's descriptor.

    does there any setting I need to set to make the value from 64 to 512?

    I have built the EHCI at my OS design.


    Monday, May 23, 2011 9:03 AM

All replies

  • Why worry about that ? its an internal detail of the driver / USB standard.
    The API funcs allow you to send any size packets, it will be chopped up for you into max-packet size chunks internally.


    Monday, May 23, 2011 9:33 AM
  • Rob thanks,

    That was because I have the throughput issue. If the wMaxPacketSiz field of the endpoint's descriptor is 64, it seems USB1.1.


    Monday, May 23, 2011 9:48 AM
  • you cannot increase the EP packet size of the USB device from the USB host: that value is embedded in the USB device silicon or firmware which, I imagine, you cannot modify. In addition, if that specific USB device comply with one of the defined USB classes it may be the case that the EP packet size is specified in the class specs
    Luca Calligaris lucaDOTcalligarisATeurotechDOTcom Check my blog:
    Monday, May 23, 2011 9:59 AM
  • Luca thanks,

    but it has different result between  CE6 and CE7 using the same USB device.

    CE6 is 512, CE7 is 64

    So I think that is the USB host controller driver's problem, but i don't know how to configure it, or how do I do with it.

    Monday, May 23, 2011 10:52 AM
  • Hi,

    Just a guess may be the device is not enumerating at High Speed?

    If so, using analyzer and see what is happening on the bus.

    Thank You & Regards,


    Tuesday, May 24, 2011 3:28 AM