I've been meaning to put together a (semi) universal ASCII keyboard for vintage computers. I decided to use KiCad rather than my tried and true Altium so that the result would be available to be modified by anyone. Last night, I bit the bullet and plowed through the KiCad learning curve, and managed to get the first cut, which I have on GitHub.
The first cut is basically an OSI 542 vanilla polled keyboard, but I've replaced the 8T26's with a pair of 74LS240's, and the 7475's with a 74LS373. (HC parts will fine as well). I've left room to escape the connector to a blank area of the board, which can be used for extra functions such as:
- Module to provide advanced features of 542B/C, which can also be added to stock 542 keyboards (compatible with 16-pin header)
- Shift-lock emulation
- ASCII keyboard emulation with parallel out
- Different polled keyboard emulation (using a 2-port RAM)
- Serial keyboard emulation with PS/2 or USB interface
I would appreciate any feedback. I'll probably throw in an AVR or PIC and create a stabilizer PCB before sending it off in the next few days.