X-Arcade on Amiga?

[adolescent]

You could probably wire up the x-arcade directly to the joystick ports.  For more two buttons you could use the Genesis layout, or if you want more use the CD32 schematics to build an adapter.

[adolescent]

Typical one button stick (Atari style):

1     Up
2    Down
3    Left
4    Right
5    NC
6    Button1
7    NC
8    Ground
9    NC

Typical two button stick (Sega Master System*):

1     Up
2    Down
3    Left
4    Right
5    NC
6    Button1
7    NC
8    Ground
9    Button2

* On the Genesis/MegaDrive Button1=B, and Button2=C.  On the Genesis, pin 7 is used to select between layouts.  Genesis 6 button pads have an additional chip inside to enable the extra buttons.

The easiest thing to do is directly wire the two button style stick.  This should sufice for a majority of the games.  Building the CD32 circiut is a bit more involved and could be left for later.

Oh, and the real thing to worry about is if the X-Arcade itself is doing anything funny.  (ie. if it already has a multiplexer...)  Do you have a pinout for the X-Arcade connector?

[adolescent]

Ouch.  Never mind, I just checked the website and this isn't going to be easy.  The X-Arcade shows up as a PS/2 keyboard.  Sorry to get your hopes up, but without re-wiring the X-Arcade itself it's not going to be as simple as I made it sound.