Arduino_X-Arcade_USB-adapter

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

D9-connector -> Arduino
5 -> 3 (clk)
6 -> 4 (data)
1 -> Vcc (5V)
2 -> Vcc (PS/2-mode)
9 -> Vcc (5V)
Shield -> GND

Library: PS2KeyRaw

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

PS/2 keyboard not needed.

Takes only about 10mA.