1.5 KiB
Interfacing a PS/2 keyboard
Serial connection through ACIA is nice, but you are probably plugging a modern computer on the other side of that ACIA, right? Let's go a step further away from those machines and drive a PS/2 keyboard directly!
Goal
Have a PS/2 keyboard drive the stdio input of the Collapse OS shell instead of the ACIA.
Status: work in progress
Gathering parts
- A RC2014 Classic that could install the base recipe
- A PS/2 keyboard. A USB keyboard + PS/2 adapter should work, but I haven't tried it yet.
- A PS/2 female connector. Not so readily available, at least not on digikey. I de-soldered mine from an old motherboard I had laying around.
- ATtiny85/45/25 (main MCU for the device)
- 74xx595 (shift register)
- 40106 inverter gates
- Diodes for
A*,IORQ,RO. - Proto board, RC2014 header pins, wires, IC sockets, etc.
- AVRA
Building the PS/2 interface
TODO. I have yet to draw presentable schematics. By reading ps2ctl.asm, you
might be able to guess how things are wired up.
It's rather straigtforward: the attiny reads serial data from PS/2 and then
sends it to the 595. The 595 is wired straight to D7:0 with its OE wired to
address selection + IORQ + RO
Using the PS/2 interface
After having built and flashed the glue.asm supplied with this recipe, you end
up with a shell driven by the PS/2 keyboard (but it still outputs to ACIA).
There are still a few glitches, especially at initialization or at connect and disconnect, but it otherwise works rather well!