Digital 5200 Controller: Instructions.

[Aswald]

PART ONE: WHAT IS IT?

When the Atari 5200 was released in late 1982, it was an attempt by Atari to match the ColecoVision.

As a result, it had a good number of arcade-to-home translations, including Atari arcade games (before mid-1984, "Atari" was a single huge company).

Unfortunately, Atari was to make a technical decision that really ended up hurting 5200 sales: the console was released with strange controllers which did not self-center, and were "analog," not "digital."

"Digital" simply means on or off. When you move a regular joystick controller in a particular direction, you activate a switch that allows current to go through. This tells the game that you are doing something. When you move diagonally, you are simply activating 2 such switches at the same time. The fire buttons work the same way.

"Analog," however, means not only on or off, but how much. A light switch with a dimmer is a perfect example of this. With the 5200 joystick, when you moved the stick in a particular direction, the game not only knew which direction the stick was moved, but by how much. This is very clear in Missile Command- move the stick a bit to the left, and the cursor moves a bit to the left, and then stays there. Move it more, and the cursor moves more. How far the cursor moves depends on how far you move the stick over.

Unfortunately, there wasn't a single arcade game from that era, to my knowledge, that had such a control scheme. Most had regular joystick controls; a few had trak-balls (Centipede, Missile Command) or paddles (such as Super Breakout). As a result, it was next to impossible to react very quickly, with short, precise moves. And while it did work moderately well for Missile Command, it just wasn't as good as paddle controls for Super Breakout.

It was just a rotten idea.

[Aswald]

PART TWO: HOW DOES IT WORK?

Using a 15-pin cable, the 5200 controller had a joystick with 4 fire buttons (2 on each side: upper and lower) and 15 buttons. These were the standard 1-9, 0, and * and #- just like on a touch-tone phone- below the joystick. The extra 3 were above the joystick and were START, PAUSE, and RESET. All but the latter 3 had different functions for different games.

The buttons actually were pretty standard as far as circuitry went. When you pushed the button, a small piece of conductive material would touch 2 halves of a sort of disc-shape. Each half simply connected to two particular wires, so, when you pressed a button, it was like touching the ends of 2 different wires to each other.

The joystick, however, was anything but standard. What the set-up actually did was to turn two different "potentiometers"- variable resistors- which are simply like two tiny paddle controllers. It was literally like having two paddle controllers: one for up and down, and one for left and right.

"Resistors" are things which limit the flow of electricity, just like a faucet limits the flow of water. The higher the resistance, the less flow of electricity you have. The lower the resistance, the more electricity flows. Resistance is measured in "Ohms." A 100 Ohm resistor will limit the flow of electricity twice as much as a 50 Ohm resistor.

A "potentiometer" is simply a resistor which can be adjusted- just like a faucet. Turn it one way, and the resistance increases; turn it the other way, and it decreases.

The 5200 joystick can turn both potentiometers. One controls the vertical; the other, the horizontal. The 5200 games act based on the two values.

In just about every 5200 game, it works like this:

VERTICAL= Increasing resistance moves DOWN. Decreasing resistance moves UP.

HORIZONTAL= Increasing resistance moves RIGHT. Decreasing resistance moves down.

Therefore, when you move the joystick left decreases the resistance in that potentiometer. Pull it down, and you are increasing the resistance in the other one.


The easiest way to see this is to plug in most games, and, after starting it, unplug the controller. You are completely breaking the circuit for both vertical and horizontal; this is "near infinite" resistance. Which way do you think the (whatever) on the screen will move?


If you answered "down and right," then you've got it.

[Aswald]

Next time: the wires, and where they go in the plug and what they do (esp. in combination). This includes instructions for doing this with ANY 15-wire cable that can plug into a 5200 (even if the colors are different).

I have drawn up several diagrams for the joystick circuitry. If someone here can put them up here, I'll send them on over next week sometime.

[Pantechnicon]

Please include pictures of the finished product so that we have some sort idea as towards what we're working to build.

[Mitch]

Have you seen this website? http://www94.pair.com/jsoper/gen_2_5200_adap.html

It has plans for a 5200 analog to digital control circuit.

Mitch

[Aswald]

I've already posted two links so you can see what the final contraption looks like. It would be pointless to go into to much detail; do YOU plan to use those two same exact things? Do YOU plan to use thumbtacks and pieces from a busted 1970s VCR? Velcro and Gorilla Glue? It's a near-miracle that this thing works and looks as good as it does!

The instructions I'm giving are meant to show everyone the workings behind it, so anyone can build one from scratch, if need be.