[Frank Adams] liked the keyboard on his Lenovo ThinkPad T61 so ... They generally use a flexible printed circuit (FPC) “ribbon cable” of some type, but may also be terminated in any number ...

(1) Most QWERTY computer keyboards use a single rubber-like membrane underneath the keys that makes contact with a circuit board when the key is fully depressed. Also called a "dome switch ...

which relies on the Adafruit Feather nRF52840 and will readily work with Palm III and Palm V keyboards. Since the PPK is RS-232 and needs to be TTL, this circuit also needs a voltage level ...