Before we set out hacking, let us first check the lay of the land, beginning with a ten cent description of what a pinball machine is.
A Pinball Machine consists of a set of circuit boards comprising the computer and specific electronics required to drive the lights, switches, solenoids, displays and sounds. These boards are connected by many many feet of wiring through the cabinet to the playfield where all the action happens. The switches, sensors, lights and fun gadgets (like our Satellite dish) are arranged on the playfield along with inanimate objects like posts, rails and ramps to create the unique flow of the game. ROM chips on the CPU board are programmed with the rules that govern the game, detailing the cause and effect of various shots (commonly referred to as Game Rules and Shot Charts). Additional chips carry the sounds and graphics unique to the game.
We will begin by focusing on the electronics. Read on for a breakdown....
For this project it helps to consider the machine as a set of discrete systems, each to be tackled individually:
Dedicated Switches , or switches that are wired direct to the CPU board as they warrant special treatment. (On our machine these are the service switches found just inside the coin door.)
The Switch Matrix , comprising all of the other switches on the machine. Anywhere a ball contact is required to affect game play, there is a switch or sensor of some type that will trigger an action. I'll describe why it is a "matrix" a bit later.
The Lamp Matrix , drives all of the lights that are required to turn on and off reflecting actions and states in the game. This matrix drives all of the lights in the game except the flash lamps and general illumination.
The general term of Coils is given to all of the items that require quick and generally higher voltage bursts of electricity (the slingshots, jet bumpers, kick ups, any playfield gadgets and high current flash lamps) . In practice, Coils fall into three categories: High Current (50V), Low Current (20V) and Flash Lamps (20V). Basically anything that needs fast switching of greater than 18V. When we get to breaking down the wiring on the I/O driver board, you will see why this collection makes sense.
Flipper Control requires some interesting electronics. Historically, flipper control electronics have caused some of the most detested problems with pins.
The Dot Matrx Display (or segmented LED display on older CPU driven games) is probably going to be the trickiest bit for us to take control over.
Sound generation consumes a large part of one of the major circuit boards. Currently, I have no plans to attempt to use the on-board sound generator. Instead I plan on dropping in a complete new sound system.
That's basically it. We will come across some other items of note as we progress, but if we can take over the Dedicated Switches, Switch Matrix, Lamp Matrix, Coils, Display and Sound, we will be in complete control of the pinball game.
Enough of this planning! Its time to gets hands on.