I have received an old POS terminal with what was supposed to be Wacom-compatible touchscreen. However, after painstaking investigation with ChatGPT, it turns out the protocol was rather incompatible with the typical modes: it sends at 9600 baud five-byte packets starting with 0xC8 for touch and 0x88 for release, with the coordinates encoded in the following four bytes. Is it compatible with any known Wacom formats? I can provide more detailed summary on the possible encoding, if needed.
For now it is working with a Python script to emulate a mouse, but it would be nice to find a proper implementation. On the other hand, given the age of the machine, doing anything more with it would not be worth the effort.