HID Report Descriptor

Projects Programming
1

Guys,

Here's a little back story: I'm working on a rfid reader and interfacing it with the arduino Leonardo, and attaching it with a Square Register.

You can read this thread for more details, about the project.

https://forum.arduino.cc/index.php?topic=578694.0

Right now, I'm trying to mimic the HID keyboard emulation as it is for a barcode scanner.

Problem is I don't quite understand the USB Report Descriptor Format.

//  Keyboard
    0x05, 0x01,                    // USAGE_PAGE (Generic Desktop)  // 47
    0x09, 0x06,                    // USAGE (Keyboard)
    0xa1, 0x01,                    // COLLECTION (Application)
    0x85, 0x02,                    //   REPORT_ID (2)
    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)
    0x81, 0x03,                    //   INPUT (Cnst,Var,Abs)
    
  0x95, 0x06,                    //   REPORT_COUNT (6)
    0x75, 0x08,                    //   REPORT_SIZE (8)
    0x15, 0x00,                    //   LOGICAL_MINIMUM (0)
    0x25, 0x73,                    //   LOGICAL_MAXIMUM (115)
    0x05, 0x07,                    //   USAGE_PAGE (Keyboard)
    
  0x19, 0x00,                    //   USAGE_MINIMUM (Reserved (no event indicated))
    0x29, 0x73,                    //   USAGE_MAXIMUM (Keyboard Application)
    0x81, 0x00,                    //   INPUT (Data,Ary,Abs)
    0xc0,                          // END_COLLECTION

I know I'm supposed to look at the HID Usage Document 1.12 as provided by usb.org, but I don't quite know how to interpret the above data.

Can anyone please explain ?

Thanks.

2

There is a USB keyboard library that sends key strokes. It handles all the details of the HID report. It works on Leonardo among other boards with 32u4. Keyboard - Arduino Reference

3

I know. That code is an excerpt of that Keyboard Library. I am trying to mimic a barcode scanner, and I'm not sure if a traditional barcode scanner uses the same reporting descriptor as that of a USB keyboard.

My question was, if anyone could help me understand the Report Descriptor format.

4

This HID Tutorial seems to go through and give an explanation by working through some examples.