hid-data example with different HIDReportDescriptor

2008-10-18T18:02:27+02:00

Hi.

I have successfully tryed the hid-data example provided with avrusb after fixing the command line tool.

Now i have changed back the Report to my previously working keyboard copyed from HID-Keys:

Code:

PROGMEM char usbHidReportDescriptor[35] = { // USB report descriptor
    0x05, 0x01,                    // USAGE_PAGE (Generic Desktop)
    0x09, 0x06,                    // USAGE (Keyboard)
    0xa1, 0x01,                    // COLLECTION (Application)
    0x05, 0x07,                    //   USAGE_PAGE (Keyboard)
    0x19, 0xe0,                    //   USAGE_MINIMUM (Keyboard LeftControl)
    0x29, 0xe7,                    //   USAGE_MAXIMUM (Keyboard Right GUI)
    0x15, 0x00,                    //   LOGICAL_MINIMUM (0)
    0x25, 0x01,                    //   LOGICAL_MAXIMUM (1)
    0x75, 0x01,                    //   REPORT_SIZE (1)
    0x95, 0x08,                    //   REPORT_COUNT (8)
    0x81, 0x02,                    //   INPUT (Data,Var,Abs)
    0x95, 0x01,                    //   REPORT_COUNT (1)
    0x75, 0x08,                    //   REPORT_SIZE (8)
    0x25, 0x65,                    //   LOGICAL_MAXIMUM (101)
    0x19, 0x00,                    //   USAGE_MINIMUM (Reserved (no event indicated))
    0x29, 0x65,                    //   USAGE_MAXIMUM (Keyboard Application)
    0x81, 0x00,                    //   INPUT (Data,Ary,Abs)
    0xc0                           // END_COLLECTION
};

I wasnt expecting it to work, but it works perfectly.

So i wonder what is the difference between both Reports?

I can see different hex values but i dont know what they means.
For instance ones have REPORT_COUNT (128) and the comments says that the report consists in 128 opaque data bytes, and in this report i have REPORT_COUNT (1), so this means "1 opaque data byte".
Then why is the transfer working?
I can write and read all 128 values with hidtool.

My usbFunctionSteup is as follow:

Code:

case USBRQ_HID_GET_REPORT:
   // wValue: ReportType (highbyte), ReportID (lowbyte) 
   // we only have one report type, so don't look at wValue 
//               buildReport(keyPressed());
//               usbMsgPtr = reportBuffer;
//               return sizeof(reportBuffer); // This will always be 2

   // fallback and use usbFunctionRead() to obtain data 
case USBRQ_HID_SET_REPORT:
   bytesRemaining = 128;
   currentAddress = 0;
   return USB_NO_MSG;  // use usbFunctionWrite() to receive data from host

The 3 commented code lines seems to not be needed for the keyboard to work.

Statistics: Posted by epsilon_da — Sat Oct 18, 2008 6:02 pm

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hid-data example with different HIDReportDescriptor