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HID Device Mystery/Misery

Hello,

Total newb here. I'm writing a driver for a HID class input device that I don't have any documentation for. By poking around, I've figured out the format of the data that the device provides (the device is like a graphics tablet). Of about 19 HID elements that I can get with <x-tad-smaller>IOHIDDeviceInterface.</x-tad-smaller>getElementValue(), 7 are actually interesting -- the rest return zeros or other data that doesn't seem affected by drawing the the stylus. So far so good.

Then I went to run the driver on another machine and it didn't work, so I looked at the HID element data again. On that system, there are five interesting elements with more or less the same data as the other ones but in a markedly different format.

I've now tested about five different configurations of systems (G4 laptop/10.3.8, G4 desktop/10.2.8, G4 desktop/10.3, G5 desktop/10.3.7, G5 desktop/10.4) and 3 of them use this second format, while two use the first format. Furthermore, there's no rhyme or reason to which systems return which data format.

I'm just really confused about what's going on here and am not sure where to turn. I really don't know very much about HID devices and am quite surprised that (a) the device returns two different data formats depending which system it's attached to, and (b) that there isn't any logic to it. Can anyone give me some clues what might be going on here?

Thanks,

Brent Marykuca
IOHIDNewbie

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