Yes, it would be horrendous! Perhaps you see why I said that. If they had to come up with ONE schematic, one that works, of course, they'd see to it that they were all designed in the same way, rather than dozens of versions having dozens of slight differences, some of which mean nothing, though they add to the general confusion. The result seems to be that many home-builders of these circuits make unwarranted assumptions about the interchangeability of certain components.

There needs to be one and only one "programing circuit" for all, meaning absolutely all, programmable components. Since, for many "real" programmable parts, this means JTAG, I believe that all new components should be programmable via JTAG or an electrically JTAG-compatible signaling scheme. That's right, no RS232, No MAX232, no USB, just TCK, TMS, TDI, and TDO, and a power supply pair for reference, though that should probably be optional. That would mean that anyone who has a JTAG cable regardless of how it is pinned out, would, ultimately, have what he needs.

One of these days, probably not soon, I'm going to try to whittle up an adapter that works on this principle ... just one ... in order to prove that it can be made to work.

The chatter about "programmers" is probably due to the fact that there are many little business-card-sized devices sold as programmers, capable of programming one or two devices serially. Sometimes they even function! Even the MCU makers sell the things.

RE