Building my new Arcade Machine - Part 2.

Building the Controller board.

Building an arcade cabinet is challenging enough, but I also wanted to build my own controlle
r board. This is the electronic controller thatinterfaces the computer with the arcade buttons and joystick. There are a few commercially available boards available, but I wanted to save a couple bucks and build my own. I was also looking forward to the challenge of doing it.

The method is pretty straight forward - hack a keyboard. Since MAME uses a computer keyboard to control everything, all I needed to do was rip some poor unsuspecting keyboard asunder, and use the small electronic board inside to connect up to my arcade buttons. This is actually slightly challenging, and requires a lot of patients. I went through a few keyboards before I found one that would be easy enough to work with my system.

If you've never seen the inside of a computer keyboard, you may be surprised to see that there is not a lot there. It's basically just two thin sheets of clear plastic with wire tracings that meet up at the position of every key of the keyboard. All these tracings then lead to a small control board, in most cases, about one inch by four inches. The tracings form a complex matrix that in turn allows the electronics to know which two tracings are connecting a circuit. It's pretty

amazing looking, and I'm sure that some poor guy had one heck of a time figuring this out for the first time.

What I then needed to do was map out the tracings to the specific keys that I wanted to use on my arcade machine. There are some standard keys that you us

ually use with MAME games. For example, the '1' key is the player one start button. The '5' key is the player one insert coin button. I needed to decide which keys I needed to use, and map them out.

At this point in the design process I really hadn't made a final decision on the layout of my controller, but I wanted to get started in the mapping process. So I decided to just map everything while I was at it, and make my final decision later.

There are a couple of ways to do this mapping. I could visually follow each path, and not were it intersects with other paths, and then figure out what keyboard key it was. I could use a multi-meter and point and note each keys location. In the end I decided to be a little more creative, and devised a more visual method for finding the key locations on the keyboard.

Using my scanner I scanned in each side of the plastic film, and popped them into photoshop. I then used the fill bucket to fill each tracing with a different colour. Then all I had to do was look at where each key location was and note the two colours. In this way I was able to map all the keyboard key colours, and which pin was which colour.

I numbered one back of pins on the controller board, and lettered each pin on the other bank. I then made up a sheet with key colours, and was able to translate them into pins. In this manner, pin E-18 could be the 'ESCAPE' key location. Which is another important MAME key.

Once I had the keys mapped, I then had to figure out exactly which keys to use. So I made a decision on what my controller would look like, and which keys I was going to use. I mounted the keyboard controller to a small board, and began wiring out the keys I needed.

In the end, it took me about 2 hours to complete the entire task.

The keyboard was $10, and the wire connectors were about $4. So I built my controller for about $14, saving about $46 and giving me a feeling of accomplishment to boot.