- The PCBs for the whole project (either SOL or classic style) are about $20/set in quantities of 5 from china, so a group buy helps.
- The parts for the interface are perhaps $10, depending on what you have on hand.
- The keys could be as little as $20 if you go with the futaba keys, although Cherry MX clones can be had inexpensively as well.
- If you want the classic-style ASCII layout, the keycap set is about $60. If you want the additional Sol-20 keycaps, then that's another $60 (Keycaps are pricey, and the Sol-20 extension set has bigger keys, some with LED window).
So, you're looking at something on the order of $110 for a new classic ADM-style keyboard, $170 for a Sol-20 keyboard replica. But that could be more or less, depending on your switch preferences, and what you have on hand.
However, the keycaps are on order and are probably on hold until the state of Washington is out of lockdown, which could be a few months for all we know.
If you are happy with a Selectric-style layout (1-!, 2-@, 3-#, ...instead of 1-!, 2-", 3'#, ...), then you could get very close with a set of PC-104 keyboard keys (double-shot molded ABS SA profile keys can be found for about $25/set). You would need 1.5u SHIFT and RETURN keys; you could use
blanks though. That would cut the overall cost down to about $80. Less if you already have keys or keycaps, and much less if you have both keys and keycaps on hand.
The source is not really targeted for the Atmega chips. The bulk of the code is portable ANSI C99, and the Atmega-specific code consists of a few functions in an architecture-specific file. It would be trivial to port to a PIC or an ARM chip. Picking a chip with more I/O would save a few bucks by not requiring any additional ICs.
I have sent off gerbers for the latest revisions, so I will have 5 board sets available in a week, if you're interested.
Dave