Homemade PS2 Controller to Atari Joystick adapter using Arduino uno R3. This Project is based on the PS2X_lib example code.
This sketch is now complete. You can hook it up to your atari according to the design in the images. In words:
PS2 Controller - Arduino
1 ----------------- 8
2 ----------------- 12
4 ----------------- GND
5 ----------------- 3.3V
6 ----------------- 11
7 ----------------- 10<
Atari Port - Arduino
 
1 -------------- 7
2 -------------- 6
3 -------------- 5
4 -------------- 4
6 -------------- 2
7 -------------- Vin
8 -------------- GND
Upload the code and you are done.