And we’re rolling
I had the idea that I would stick an attiny84 in the open area to the right of the ’85 but after dinking around with the software for a while and looking at pin assignments I decided to bite the bullet and use a mega. I don’t like destroying a working circuit but i grabbed the original iteration which used the 1802’s N1 signal as clock and cleared off that area. The mega fits in fine of course and there’s a little bit of room left where I might be able to shoehorn the iscp header.
Using the mega means the fewest changes to the olduinoISP software. I still have visions of switching to an attiny for the next iteration but that will mean a new board.