Ewan's Musings

Mame Controls

The day to day use of your Mame cabinet is going to be through the stick and buttons on the control panel, so you need to spend some time designing it and laying it out. For the moment, consider what games you think you'll want to play, how many buttons you need to play each game, and if things like a trackball or spinner are going to be needed.

I dropped the idea of trackball and spinner rather quickly, and gave myself a two player "fighting Game" layout of an 8 way stick and 6 buttons per player. This gives a lot of versatility and allows the majority of (non driving) games to be played. While a trackball is seen as a good mouse replacement, a good setup in software will mean that you don't need to resort to needing a mouse or full keyboard input (but we'll come to that later).

Mame works on a desk bound PC by picking up a keypress, and translating this in the software to the relevant input for the arcade machine being emulated. So whateer controls you have on the front of the cabinet need to be directed to your PC as key presses.

The original Mame Cabinet builders used what's called a Keyboard Hack. This involved a normal PC keyboard being stripped, and the relevant connectors underneath the physical keys wired to the control panel buttons. While this works, there is one major problem that stops it being a good solution.

Keyboard Ghosting is where you press three of four keys on a keyboard at one time, and get a different key signal sent to your PC, or some of the keyboard presses ignored altogether. While you might not have problems playing a sedate game of Pac Man, with two players each trying to pull off a special move in Street Fighter 2 (which could mean 8 or 9 keypresses all held down at the same time) keyboard ghosting is goign to completely destroy any arcade game.

The solution is a simple one. Ultimarc (based in London) have built one of the most popular bits of kit for Mame Cab builders in the world. The Ipac Circuit board plugs into the PS/2 keyboard socket on your PC through an extension cable, and then you can plug your regular keyboard into a through port on the Ipac. Onto the Ipac you connect the microswitches from the arcade control buttons and they reflect the nessecary key press signals to the PC, or allow you to use the real keyboard without having to play with switching boxes or other silly things.

Here's the birds nest of wiring underneath the control panel. It's taken from behind the cabinet, looking out the front. On the top right you can see the Ipac circuit baord, secured underneath the monitor shelf. The base of the red blue and green switches can be seen, with the microswitches fixed to the bottom (you can see that best on the green switches). Finally, the keyboard wired through the Ipac is sitting below all the wiring.

I've added three extra buttons over the standard Player buttons and Start buttons. One of them is a third green button. This is there to be used as a 'spare' button and I currently have it set up as a 'pause' button - something the original arcade machines never had, but dead useful when Eilidh needs a nappy change. The second and third buttons aren't mounted on the control panel, but on the door where the coin box should be. Pressing either of these two black buttons simulates a coin going in.

This last picture shows how I can get to the keybaord and mouse while using the cabinet. The whole front panels hinges down, and pulls out a shelf where the keybaord and mouse rest. You can also see the PC behind the coin door, and the wiring for the coin buttons .