So I’ve decided on some Arduino soldering over the next few days. Fitting a fiddly SOIC F-RAM and some other components to a prototype shield. It should be fun. Then I have to fit some more code into the 32KB, and then work out a test bed and a box. I’m sure I saw a MIDI device code for the ATMega which does the USB handling. This could be useful later, but I think it does destroy the ability to connect direct with a terminal console.
The F-RAM adds 64KB of slower but fast enough memory to the Arduino, so that more complex projects can be assembled on this prototype. A display is also planned as is some analog pots and a button. Should be fun.