Got me thinking though... rather than playing about with a keyboard, about time to make a completely PC compatable arcade controller for playing anything on the PC, emulators, etc.
The best way to make something compatable with the PC is to use something that is 100% designed for it - no configuration, etc needed.
Decided therefore to use an old computer keyboard and map the buttons on the controller to them.
The PS1 ASCIIware Arcade Stick unit cost £1.50 at a car boot sale; and the keyboard 50p; so the project cost is £2 plus spraypaint, solder, % use of soldering iron, etc - so under £5 for the whole project!
Anyone got a cool name BTW for this project, please post it!
Anyroad, here are the two items - you notice the keyboard is a PS2; can be used as that, or with a £3 adaptor can be made USB easily.
The two components:

Unscrewed the keyboard, all the tiny bits are just rubber domes designed to raise the keys after being pressed.

Turns out there are two acetate sheets with metallic traces printed on top, and in the middle a plain piece of acetate with holes cut out for the contacts. When pressed together, contact is made and keyboard button is activated. I have seen this before on keypads. The middle plain acetate sheet is there to stop the two other sheets from touching.

This is the board that makes it work:

Removed the rest of the keyboard casing and just kept that part.

The arcade stick:

Opened up, two screws hidden under the pads.

Nice and easy - just need to wire to the traces for the buttons and modify the board a little.

All disassembled, including the joystick.

All I need to do is wire to some keyboard contacts, fold the rest of the acetates into a roll so it all fits in the arcade casing; connect those keyboard contacts to the buttons in the arcade stick sections, change the board a bit; respray the case and buttons (metallic purple and black); job done. Just a few hours work.

