This is the cabinet interface page

For MAME on the PC to be controlled by joysticks, buttons, trackballs, and so on, you need a way to connect the inputs to the computer. This is the interface between the control panel and the PC.

Why it's necessary

MAME uses keyboard input to simulate arcade cabinet controls. As an example, the player one joystick control is simulated by the arrow keys. When playing Pacman on MAME on a PC, for instance, you can steer your chomping Pacman character around the screen using the arrow keys.

Why keys instead of a "real" joystick interface? You'd have to ask the MAME developers for the answer to this. I like to think that is was a conscious decision based on the way that actual arcade machines work. You see, most older machines used analog joysticks—essentially a stick that pressed switches depending on which way you moved it. This switching mechanism has a close parallel in keyboard input.

Mangling a keyboard

One possible solution to the interface issue is to cannibalize an old keyboard and turn it into an interface. You can "hot wire" a connection between your buttons and joysticks so that when the switches that comprise these components are switched, they "press" the appropriate key by closing the switch under the keys on the keyboard. This method is for the intrepid do-it-youselfer, and requires a good deal of patience.

The primary downside to this method are two somethings called ghosting and interference. Due to technical details that I won't go into here, simultaneous presses of multiple keys can result in the keyboard controller sending a different code (ghosting). You can think of this by imagining that you simultaneously pressed A and B, but the character C was sent from the keyboard to the PC. Interference results when too many simultaneous presses result in some of them being lost" You can think of this by imagining that you simultaneously pressed A, B, and C, but only A and B were sent from the keyboard to the PC.

Mangling a mouse

For a spinner control, you can modify a mouse. There are a number of sites on the Internet that explain how to do this. I made an attempt at creating my own spinner from a surplus mouse, but decided not to pursue this. Why? Because for a good "feel" you need a heavy knob and bearings, and I don't have a CNC machine to mill something out.

 

 

Buying an interface

You can also opt to purchase an interface. Ultimarc has excellent interfaces. Their button interface is called the I-Pac. The I-Pac comes in various configurations for up to four players worth of buttons. The image below is the four-player type I-Pac that I have in my cabinet.

The Ultimarc mouse/trackball interface is called the Opti-Pac. The Opti-Pac provides an easy way to connect a HAPP (or other manufacturer's) trackball or an Oscar spinner to your PC for control of games. A spinner is essential for Tron or Tempest. You need a trackball for Centipede, Missile Command, Marble Madness, etc. The image below is the Opti-Pac.

One big advantage of the I-Pac and Opti-Pac solutions are that they support the USB standard. So these are really plug-and-play under Windows, which tends to make things much more simple.

 

On to the exterior finish page