I2C protocol for touchpad module

[cscott]

Again, thanks so much for the information provided in #8.

There have been requests to create alternate touchpads, and the missing piece to do this (other than #9, the mechanical specs) would be details of the I2C protocol spoken by the touchpad. There is a "HID over I2C" thing, and if that's what's going on here than probably just stating so would be enough. If its a bespoke protocol, then we'd probably need the datasheet for the stock touchpad used in the FW16 so we could emulate it properly.