I searched my mailbox for kbdd related mails and found that someone already wrote support for this keyboard some time ago and sent me modified kbdd code and I forgot about it completely since then. I'll make proper diff and update kbdd binary with elektex support ASAP. Also I add source diff to my page

Looks like this keyboard sends real keycodes after all so it is not as dumb as I thought :-( This is unfortunate since having raw coordinates would allow us to change the layout and/or make additional buttons and do something fancy with pressure data too. Also it means that the calibration is unfortunately not supported since it indeed needs some bidirectional communication which is impossible to determine without sniffing real communication done via official driver.

Hmm, I wonder why they cared with implementing translation/calibration layer in the keyboard directly and still went with SPP profile and custom driver. Having the device to just passively send coordinates and leave rest to the driver would be IMO cheaper and simpler. Bluetooth SPP profile allows passive devices with one way communication to save costs.