This is a simple to build adapter for connecting Mega Drive (Genesis), Master System (+ Atari and C= controllers) to USB. It supports 3 and 6-button Mega Drive controllers and 1 and 2-button SMS/Atari/C= controllers.

The input lag for this adapter is minimal. Here is the result from a test with a 1ms polling rate on a MiSTer:

Controller	Samples	Average	Max	Min	Std Dev
Original 3-Button Mega Drive Controller	2342	0.75ms	1.28ms	0.24ms	0.29ms
8bitdo M30 Wireless 2.4G	2348	4.54ms	8.05ms	2.22ms	1.31ms

The Mega Drive gamepad interface is based on this repository : https://github.com/jonthysell/SegaController but almost entirely rewritten and a lot of optimisations have been made.

Parts you need

Arduino Pro Micro (ATMega32U4)
Male end of Mega Drive controller extension (or DSUB 9Pin Male connector and some wires)
SPDT Switch (2.54mm/0.1" pitch)
Heat shrink tube (Ø ~20mm)
Micro USB cable

Wiring

How to assemble (please ignore the switch)

(The switch goes to pins GND-GND-2 even if the picture above shows it connected to GND-2-3)

License

This project is licensed under the GNU General Public License v3.0.