I have an existing, half complete, vending machine project running on an Atmel UTC, which I want to port to the Pi.
In order to talk to peripherals, such as coin acceptor, it has to support Multi-Drop Bus which has a 9-data bit serial port interface (plus start, stop and parity bits).
I learned the hard way with the Atmel board that hacks which one finds suggested on the net, which rely on using the parity bit as the 9th data bit can cause bad timing problems - difficult to detect and to correct (so, please don't refer me to this, or similar. Thanks).
Does anyone know if/where I can buy a true 9 bit serial port for the Pi (bonus points if it can somehow work with the Pi zero).
Is there, perhaps, a Hat available? Or could I easily (I have a s/w guy, with little knowledge of h/w) use another board to handle the 9 data bit UART and control that from a Pi?