HP HP48 series calculators will allow transfer of data over RS232 and can send and receive objects as files via the kermit protocol. My goal was to be able to save or read files from an external storage media without needing a host PC to perform the file transfer.
So far I've managed to get a very simple file receive working and am implementing more of the embedded kermit functionality.
git repo is here https://codeberg.org/eugenenine/ArduinoKermit48