I recently started hacking a control interface for the system but is soon got out of hand. For example, I thought that I could get the whole thing, (buttons, ALU, display and dividers) on the same pretty narrow board.

It turns out, I can't really. I added a "bypass" system with '165 and '595 shift registers to read the buttons, and override their value, to provide external control (and debouncing, or even smooth fading) and there is not even a TIL311 or #DYPLED in sight.

So I moved the frequency/signal processing to another board behind it.

Then, other projects happened.

Anyway, I'm now having a pretty cool clock source and some PLLs so the story is not over. Yet.