I've never used one of those micromodules for development, but I have built 'em myself, albeit on a somewhat larger format. An 805x development system with an external UART is already a useful tool for general purpose development, provided you have software to support it. That way the external UART is used for development support, while the either one or two on-chip serial I/O ports are useable for the target application.

As I mentioned before, long ago it was not uncommon for me to use a single-board CP/M system, most commonly the AMPRO "Little Board", which was formatted to fit on a 5-1/4" FDD but would also fit on a HDD of the same size, and simply plug my target system into the Z80 socket on the "Little Board". This necessitated a 3-level wire-wrap socket on the target board, since it was normally a wire-wrapped board with 2-level sockets (there's never a need for 3-level sockets aside from such lashups). The same sort of thing would work in another context, I'm sure.

I think a share of the LINUX-based SBC's based on ARM9's or even ARM7TDMI would do the job nicely. Because of the "creeping featurism" there are some that won't, of course.

I'm happiest when the only involvment of a PC is as a terminal. I do have terminals, of course, and prefer to use one of them.

RE