This a very simple PS/2 interface that I made just because I can.
Currently, it handles receiving bytes from the keyboard, though it
doesn't actually verify start/end bits properly since my keyboard doesn't
actually send the stop bit as a 1?
It translates the scan codes into characters and prints them to the serial monitor.
L/R Shift, L/R Ctrl, L/R Mod, L/R Alt are handled via a bitset and checked
when a keystroke is sent to be used for translation into text Shift
translates the keys to upper case or the key that is mapped on the
keyboard (i.e. ; -> :). Ctrl/Mod/Alt are translated into <C-?>,
<S-?>, <M-?>, respectively, where ? is replaced with the character
pressed (i.e. Ctrl + b -> <C-b>).
The circuit is very simple, since hardware is connected directly to the Arduino.
The only note that I have regarding the circuit is that the Keyboard's PS/2 power is plugged directly into an Arduino output so we can turn it on manually and see any startup output. This also helps since PS/2 is not officially hot-swappable.
This is only a small personal project, so I'll probably never finish these things:
- Host -> Keyboard Communication
- I've got a basic implementation, but it doesn't seem to be happy and never sends the ACK bit or clocks. This may be because I have a very cheap keyboard (8 USD on ebay) and it just doesn't work, or I'm doing something wrong. (I'm leaning towards the latter)
- This page has some very detailed information oh how the protocol should work, and I've implemented it as far as I can tell, though still no luck. It states that the host is supposed to time out at some point, but I've not implemented this functionality yet, so it just freezes.
- Caps/Scroll/Num lock
- I'm waiting on fixing the above one before I do this, so that I can turn on the lights (:
I heavily relied on a few different sites for information about the PS/2 spec and other aspects of this implementation.