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DIY Uno Plus for Atari Trackball

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New Member
Joined: 2 months ago
Posts: 2
Topic starter  

I recently came across an Atari CX-80 Trak-ball in great condition, still in the box. I decided to pick it up, in hopes that I could play some Marble Madness on Mame or emulator. 

I came across Ali's video where he hooks up a CX-80 and thought it looked great. Since Ali generously makes the firmwares available, and I knew that he used 5V Arduino Pro Micro, I thought I might be able to put one together myself. I had a lot of silly mistakes, but I reached out to Ali, and he provided some documentation and assistance and basically coached me through the build.

I flashed the pro micro on a Windows 10 laptop, and had to use the prog2 command. Worked right away, and then i was able to move back to my linux computer and work from there. Ali provided me with the pinout documentation for the Atari controller and pro micro for the Uno Plus firmware, so I grabbed a small tupperware container, drilled some holes, started soldering, and then finally spraypainted it blue. I had a serial cable kicking around, so I snipped an end off that and fed it through the drilled hole and then glue gunned in place. I also fed a usb plug through the other hole, and glue gunned that in place, and its very solid. You need to be very mindful of the pro micro usb ports, as they are prone to snap off. I've seen it happen in several different videos now. 


Tested it in windows using the game controllers settings mode, and also tested it in linux via evtest and jstest, and it worked great. Currently it only really worked in joystick mode, as the nature of my speedy implementation meant that I dont have any buttons or screen with which to cycle through modes. Ali has offered to provide both a custom firmware that defaults to trackball mode, and also mentioned that he will detail the buttons and method to cycle through the modes. Once it is in the correct mode, it will default there even after power off. 

This was a great project, and Ali's set up here is great. Thanks!



Ali Jani
Member Admin
Joined: 3 years ago
Posts: 15

Thanks for the kind post. I like your case 🙂

See this image for details of the buttons connections on the Uno plus. be careful though as you can get yourself stuck if you press a bunch of buttons without an LCD attached to the SDA/SCL PINS hence my offer to send you the attached trackball defaulted firmware that also has mouse on by default.  Keep in mind that while in trackball mode, joysticks can wont operate correctly so you will have to switch modes if you want joysticks to work again.

To switch modes, click Blue+Yellow at same time and let go.  You can tell what mode the unit is in by how many times the led on the pro micro blink when you switch modes. (blinking is only on attached defaulted trackball build)

  • Mode 1 (normal joystick/paddles mode) - 2 blinks
  • Mode Driving - 6 blinks
  • Mode Trackball - 7 blinks

Hope this helps. let us know.

New Member
Joined: 2 months ago
Posts: 2
Topic starter  

Thank you so much! 

I have flashed the software to my build, and it is now functioning as a mouse. Thank you very much! I may also add a button to my case that is just the blue and yellow buttons wired together, with button connecting to ground, so I can still cycle through controller types with a single button! 

My cx-80 is in good shape, but at 40 years old, it could certainly use a cleaning. I am going to get it cleaned, and then try to get it up and running for a party tomorrow night, where I hope to have Marble Madness, Crystal Castles, and Irritating Maze available to play. 

I leaned a lot working on this project. Thanks again Ali! Next time you are in the east coast of Canada, give me a dingle and you can come over and admire your handiwork and we can get our game on. 

Do you have any favorite trackball related games you would recommend? I have mame and all emulator set up on a pc. 


Thanks again Ali!



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