Sunday, September 09, 2007

Mouse toTrackball to Centipede

Born in '65, it's inevitable that I grew up playing arcade games in the local arcade, re-discovered the joy of the simple games of those days and found my way to the MAME project.
I downloaded the the MAME executable and a bunch of (illegal...?) games, and I carried it with me several years, copying it to every new PC, and occasionally playing some of my favourite games. What always created a slight itch was the fact that playing on a computer keyboard does not really come near the 'real arcade experience'. So, like many others.. I would love to build a real arcade cabinet, with real joystick, trackball, spinner and fire buttons. Of course I lack the time to build it, a place to store it and even time to play it, but the idea remains. Looking around I found several on-line shops that sell all necessary parts from controls to marquees to make it look exactly like the original, but adding it all together it gets quite expensive. Certainly controls like a trackball and a spinner are costly items. And actually a spinner does not seem like a difficult thing to make yourself, but I decided to start with the trackball, since I already owned this. It is a Wico-trackball that was manufactured in 1983(!) for the then popular TI-99 home computer. Actually this seems bad timing, since TI exited the home computer market by the end of '83... Well, I bought the trackball a few years later for a few bucks, and first interfaced it to my Commodore 64, but hardly ever used it. Since a trackball and a standard computer mouse (the ball type) are very similar I thought it would not be too difficult to combine the two and have a 'mouse compatible' trackball. Fortunately 'standard' mouses can be found in large piles lying around unused in almost every office, so I soon found a suitable Logitech USB type that no one cared about anymore. First I thought it should be possible to use the original optical switches of the Wico, and just wire these to the mouse electronics. But since neither the mouse nor the trackball switches have any type numbers stamped on them so I could not easily compare the connections and make a new routing plan, I decided it would be easier just to remove the switches from the mouse, and mount them inside the trackball, completely discarding the original trackball electronics. So I just removed the Infrared LEDs and the opto switches from the mouse board, mounted them on a piece of prototyping board, and re-wired them to the original contacts. The image here shows the result. Bottom right you see the original mouse electronics. Bottom left you see the piece of prototype board holding the LED and the opto-switch. Right top you see a little piece of the second board just before it's put in place. Top left you also see the contacts of the 'fire' button. The wires from this I just cut to the right length and soldered them to the rear of the switch that used to be the left mouse button.
And it works great!. Finally I can play one of my favourites (Centipede) the way it was intended. So now I'm ready to take the next step: build a 'Rotary controller' or 'Spinner' for my all time favourite game : Tempest .Right now I'm chasing another unused mouse...