Arduino-USB-HID-RetroJoystickAdapter/X-Arcade/README.md

Arduino_X-Arcade_USB-adapter

"Old" PS/2 -version of X-arcade.

D9-connector -> Arduino Pro Micro
6 (data) -> 3
5 (clk) -> 2
1 (5V) -> Vcc
2 (PS/2-mode) -> Vcc
9 (5V) -> Vcc
Shield -> GND

Or

PS/2-connector -> Arduino Pro Micro
Data (green or blue) -> 3
CLK (white or purple) -> 2
5V (red) -> 5V
GND (black) -> GND

Library

PS2KeyRaw

Arduino Pro Micro (select Arduino Leonardo from Arduino IDE).

PS/2 keyboard not needed.

Takes only about 10mA.