Hi, I just made this rotary joystick. Here are some pictures.
I have the rotations registering as buttons 8, 9 and 10. So, at any given time this joystick is transmitting either 8, 9 or 10.
This isn't particularly useful, because MAME needs clockwise and anti-clockwise signals sent.
So... I wrote a program to do that too
http://forum.arcadecontrols.com/index.php/topic,129020.0.htmlAnd here's a shot of the inside for those interested.