CODEWITHSUNDEEP
keyboardhidemulation
Steve
Steve

Reputation: 33

Is there a USB device descriptor to determine if a device is HID or keyboard emulation?

Does anyone know how to determine from the USB device descriptor or other USB descriptors if a USB device is HID or keyboard emulation? I'm looking to interface to a family of magtek magcard swipe readers and they can be configured to operate as HID or keyboard emulation. The magtek PID will tell me but what happens if someone plugs in a different manufacture? I'm looking for a univseral way of determining this. I'm using the libudev library to interface to my USB.

Also, does Linux have a universal routine to decode keyboard emulation scan codes. I've got my own look-up table which works fine but I was just wondering.

Steve

Upvotes: 2

Views: 1624

Answers (1)

zmo
zmo

Reputation: 24812

  1. The only way you can tell what a device is, is by using the PID/VID of the USB device (and the Class, but I believe both modes are declared as HID-class devices anyway).
  2. So, if you plug in a new manufacturer, you'll have to manually add support for it. From my experience (I did not use a magtek reader, but a tmsr33), no reader behave the same way in both HID or emulation mode. Generally speaking, I'd say it is better to use HID mode, as bytes exposed will need less conversion.

  3. AFAICT, I went into the same trouble and I basically copy pasted the keycodes/keylayout from the kernel sources to my own code. If you prefer, you can link directly to the kernel's source code to get the tables.

HTH

Upvotes: 2

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