USB Keypad

[dave]

Hello,
	I am working on a mobile device based on Raspberry Pi OS. I am using
a USB keypad to navigate the UI of my device. I have purchased 2 models. One
has 19 keys and the other has a few more. I've implemented the user-space
code to read() the input device. Things are generally working fine. But I
have one issue. On both models the keycodes I receive are not unique across
all keys. On one, the key labeled INS and the one labeled 0 both send the
same code. On the second one, the mapping is even more bizarre. It has
duplicated Num Locks and other keys, as well. The number keys are always
readable as such, but the other non-number keys can be aliased.
	My question is simple: is there something I need to do to change the
mode of the keypad to send unique codes? Perhaps an ioctl()? I do not know
the HID spec. I wonder what pressing the Num Lock key causes an OS (like
Windows) or X11 to do to change keypad modes. Is there a document or website
I can read that discusses this?
	Thank you,
	David