Atari 5200 controllers use 15 pin connectors compared to 9 pin connectors of most of their other consoles.
The schematic below shows the controller has two potentiometers that control the x and y coordinates and couple of switched for the two fire buttons, and then a 4×4 keypad matrix.
So that's total of 12 input lines needed for each joystick. 8 lines for 4×4 matrix, 2 for the stick position, and 2 for the fire buttons. To handle 2 joysticks, that means we need at least 24 input ports.
I decided to use a Pro Mirco micro-controller along with a 16 port PCF8575 I/O expander. Created a schematic below.
I wired up everything and after a few hours of coding I was able to get it to work!
I had 6 ports to spare, so I added common buttons on the unit dor things like Start, Select, etc.. I then designed the PC Board, and cleaned up the code to get it to professional quality, designed and printed a case and success!
Here is a quick video showing how it works!
Let me know what you think, and if you decide to get one, you can find them using any of the following links: