Foreword

Atari-style joysticks were the de facto standard for game controllers in the eighties. The design was first used in early Atari game consoles but got soon adopted by most home computers of the 8-bit era, best known examples including Commodore, Amstrad, Spectravideo and MSX. I still own a couple of Competition Pro sticks and just love the precise and tactile touch they provide. Pixels Past manufactures adapters that allow you to connect Atari-style joysticks into the USB port on your PC, making the OS think they are regular PC joysticks. The Stelladaptor seems to be a solid product but I think that the price per unit, at $29.95, is a bit too high for a single-joystick adapter. That's why I started thinking about building an adapter myself so I would be able to play emulated games (and others too) with these sticks.

Update

A friend of mine asked me to build a couple of these adapters for his PVR/gaming box. I told him to get two Logitech Wingman Precision gamepads for me to use as raw material but it seems that Logitech doesn't manufacture that model anymore. The old pad seems to have been replaced with the Logitech® Precision™ Gamepad, part no. 963335-0914, sometimes called Logitech Precision Gamepad Refresh. I bought one of these for 13 euros and opened it to see if it's as usable as a general USB interface as its predecessor. In short: Refresh can be used to make an adapter but it won't be as straightforward as with an older model. See my notes below for more details.

Planning

At first I thought of using PIC microcontrollers with USB support (like the PIC16C765 from Microchip Technology) to accomplish the task. But I soon noticed that the chips cost around $13 a piece (plus shipping) and decided to switch to plan B pioneered by Marko Mäkelä: exploiting the internals of a cheap USB gamepad. The best gamepads for this purpose are those with only digital inputs on them (no pressure sensitive buttons or analog sticks) so you wont be paying for parts you don't need for the adapter. Marko built two Atari connectors into a working gamepad but after I got my hands on the cheapest pad I could find - the Logitech Wingman Precision USB (9.95 euros) - I promptly decided not to follow his lead. These gamepads must be the reason word "cheap" was invented for. It's actually hard to hit the direction you intented using the stiff D-pad and the buttons don't deserve much higher praise either. So I ditched the plastic casing and concentrated on what's inside.

Pic. 1:
Logitech Wingman Precision USB, still intact.

Pic. 2:
Gee, can't say its crowded in here... The lone IC handles the USB communications and reads the digital inputs. The only other components are the voltage-stabilizing capacitors and the pull-up resistors for the shoulder button inputs.

Pic. 3:
The bottom side of the board with the button contacts.

As you see in the pic #2, the gamepad's circuit board layout is really sparse which made it easy to trace the connections from the input switches to the pins of the single IC. The chip itself is labeled:

CP5733BM
LOGITECH
3311590100 B 02
IND0424 505333

I don't know if these are used in any other controllers (probably not since more expensive pads usually have analog inputs too) but here's the pinout in case you want to hack the same gamepad or happen to find the chip elsewhere:

Note: Most computers that have Atari joystick ports provide +5 volts on the pin 7 of the D-sub connector to power autofire circuits. If you want to use the autofire function present on some joysticks, you have to connect D-sub pin 7 with the pin 10 on the IC, inserting a small resistor for safety.

Second note: Some alternate designs expand the de facto Atari standard with features like a second fire button. If you want to use a joystick that has two distinct fire buttons, you need to know which connector pin the stick use to achieve this expansion. MSX and Amstrad CPC use pin 7 for button 2 but other systems may differ. See the epanorama.net page about Atari-style joysticks if you are unsure about the connections. After you have figured out the correct D-sub connector pin, just connect it to pin 4 (BUTTON2) on the Logitech chip after which you can use the second fire button too.

Construction

After I figured out the connections there wasn't much left to do. I took a 9-pin male D-sub connector, soldered the wires into the pins required by the joystick and the other ends straight to the pins of the Logitech chip. Crude but effective.

Large areas of the board housed contacts for the gamepad buttons which I didn't need anymore so I sawed a couple of centimeters off each end. The adapter could have been a lot smaller if I had unsoldered the IC and other parts and put them on veroboard but I wasn't really looking for style points here and went with the easy solution. Finally I installed the board and the connector in a small plastic box and the adapter was ready!

Conclusion

This is a nifty way to give your old Atari joysticks a new life beside your modern PC. The total cost of the adapter might be around 15 euros, the gamepad being the biggest expense and the D-sub connector and the casing setting you back a couple of euros each. It's also easy to build - I probably spent more time writing the text on this page than putting the gizmo together... So pick up your soldering iron and get hacking! :)

Gamepad Refresh

Logitech Precision Gamepad is the successor of the older pad I inspected and used in my original Atari adapter project. Here is a short overview about the updated model in case someone is wondering if it is as hackable as the older one.