Introduction

If you want to play games on your Genesis/Megadrive console but have a strong preference for SNES controllers, or own many cool arcade sticks for the SNES which you'd like to use, an adapter to connect SNES controllers to your Genesis/Megadrive is exactly what you need.

I used an Atmel atmega8a MCU do build this adapter, and optimising the code until it would react fast enough to the console requests was a fun challenge which I took the time to document.



See also: SNES controller to Atari/Commodore adapter

Button mappings

Genesis	SNES 1	SNES 2	SNES 3	SNES 4	SNES 5	SNES 6
Start	Start	Start	Start	Start	Start	Start
Mode	Select	Select	Select	Select	Select	Select
A	A	B	Y	X	A	B
B	B	A	B	Y	B	A
C	X	Y	A	B	X	R
X	Y	X	L	A	Y	Y
Y	L	L	X	R	L	X
Z	R	R	R	L	R	L
D-Up	D-Up	D-Up	D-Up	D-Up	D-Down	D-Up
D-down	D-down	D-down	D-down	D-down	D-up	D-down
D-left	D-left	D-left	D-left	D-left	D-right	D-left
D-right	D-right	D-right	D-right	D-right	D-left	D-right

Enabling a mapping:
Mappings are enabled by holding buttons on the SNES controller when connecting the adapter or turning the console on.

Mapping	Activation
SNES 1	Default
SNES 2	Hold B
SNES 3	Hold Y
SNES 4	Hold X
SNES 5	Hold L
SNES 6	Hold R

Note: SNES 6 mapping is not available yet.

Wiring

I used a simplified version of my multiuse pcb2 for this project. The only components present are the microcontroller, capacitors, and a 16 MHz crystal.

Schematic:

Wiring:

Wiring tables for the Genesis/Megadrive (DB9-F connector) and SNES controller:

DB9 Pin	Signal name	AVR pin name
1	UP/UP/Z	PC5
2	DN/DN/Y	PC4
3	0/LF/X	PC3
4	0/RT/	PC2
5	VCC	VCC
6	A/B	PC1
7	SELECT	PD2 (INT0)
8	GND	GND
9	START/C	PC0

SNES pin	AVR pin name
VCC	VCC
GND	GND
CLOCK	PB5
DATA	PB4
LATCH	PB3

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Here are a few pictures of my development setup, all wired according to the above tables. Notice how the standard solder cup DB9-F I used to connect to the console cannot be fully inserted. Ideally a Genesis/Megadrive controller or extension cable should be used.

Firmware

Version v1.6 October 26, 2019 (Saturday)
Add a new mapping (SNES 6 - Hold R)
File(s): snes2md-1.6.tar.gz (21.4 KB) snes2md.m168.1.6.hex (6.2 KB) snes2md.m8.1.6.hex (6 KB)

Using the .hex files

The micro-controller (Atmega8 or Atmega168) needs to be programmed with the correct .hex file. The "fuse bytes" for this project are:

• Atmega8: high_byte=0xc9, low_byte=0x9f.
• Atmega168: high_byte=0xdc, low_byte=0xd7, extended_byte=0x01

For more information about the tools required to program an AVR microcontroller, please visit my AVR programming page.

Source Code (.tar.gz files):
Unless indicated otherwise, the source code is published under the GPL license. Please consult the included LICENSE file for more information. The project compiles using the included makefiles using avr-gcc under Linux.

User pictures

I like seeing how others build my projects. If you build an adapter, please send me pictures and I'll add them here.

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January 6, 2015 (Tuesday)
Roman Sysoev from Russia sent me the following pictures of the prototype and final PCB version (enclosure still missing) of the SNES controller to Genesis/Megadrive he built.

References

The following document(s) were useful:

• Sega Six Button Controller Hardware Info

Disclaimer

I cannot be held responsible for any damages that could occur to you or your equipment while following the procedures present on this page. Also, I GIVE ABSOLUTELY NO WARRANTY on the correctness and usability of the informations on this page. Please note, however, that the procedures above have worked in my case without any damages or problems.

Now you cannot say that I did not warn you :)