SMD2Wii

SMD2Wii - adapter for Sega Mega Drive controller to Wii remote.

Adapter emulates Wii Classic Controller with Sega Mega Drive / Genesis 3/6-button controller and can be used with homebrew emulators like Genesis Plus GX and selected Wii Virtual Console Games.
Work not confirmed for NES Classic Mini / SNES Classic Mini.

The goal is to connect SMD 6-button controller to Wii as cheap and simple as possible.
For NES / SNES emulators excellent Nintendo Classic Mini Controller / Nintendo SNES Classic Mini Controller suggested.

Project based on Cluster's nes2wii project with following changes:

• Controller replaced with simpler / cheaper ATmega8A
• Deleted all other platforms and second SMD pad support from source code and schematics
• New smaller PCB
• Fixed SMD 6-button pad state query errors
• KiCad 7.0 schematic and PCB sources added

Schematics

Board:

Assembled board preview without Wiimote connector:

Fuses

Bits configuration

• Low fuse: 0xC4
• High fuse: 0xD9

Compiling from source

Windows:
Install WinAVR-20100110-install.exe
make all

CH341A programmer and NeoProgrammer V2.2 software can be used for firmware .hex flashing.

Tested with

• ATmega8A-U, 8MHz
• Third party 6-buttons Sega Mega Drive controller with Mode button ("Retro Genesis 16 Bit ACSg11")
• Software: Genesis Plus GX, FCE Ultra GX, WiiMednafen, RetroArch

Modes

There are three modes for controller d-pad:

• Mode #1 - d-pad works as left analog stick and d-pad on classic controller at the same time
• Mode #2 - d-pad works as left analog stick only
• Mode #3 - d-pad works as d-pad only

Mode 1 selected by default.

You can hold Start+B+C for a few seconds to change mode. Red led will blink 1/2/3 times indicating new mode.

Bill of materials

• ATMEGA8A-U TQFP32
• DB9 PCB Connector Angle (DSUB-9 Male Horizontal P2.77x2.84mm Edge Pin Offset 7.70mm Mounting Holes Offset 9.12mm)
• Wii controller 6 Pin 90 degree male connector
• SMD 1206 Resistor 2.2k(222) x3
• SMD 1206 Capacitor 0.1(104) uF x1
• (only for programming) Connector PinHeader 2.54mm 1x06 Vertical
• (optional) Electrolytic Capacitor Radial D5.0mm P2.50mm 4.7 uF
• (optional) SMD 1206 Resistor 400 Ohm x2
• (optional) SMD 1206 LED Red x1
• (optional) SMD 1206 LED Green x1

Notes

About delays and interrupts

SMD controller polled every 5 ms. Wiimote classic controller query interrupt disabled during the poll (not sure if interrupt is delayed or cancelled).
Worst case scenario additional input delay is about 5-6 ms (or one frame).
Current code:

void gamepads_query()
{
	_delay_ms(5); // Must be >= 3 to give 6-button controller time to reset

	cli(); // Disable wiimote poll interrupt

	// 8 iterations for read controller state.
	for (b = 0; b < 8; b++)
	{
		_delay_us(2); // Short delay to stabilise outputs in controller.
		...read pad pins
		...invert SELECT pin
	}

	sei(); // Enable interrupt

See gamepads.c code comments for more details.

Buttons mapping

Classic controller to SMD buttons mapping:

a = smd.c;
b = smd.b;
x = smd.y;
y = smd.a;
l = smd.x;
r = smd.z;
select = smd.mode;
start = smd.start;

Author(s)

Original firmware and schematics for ATMEGA16A:
Alexey 'Cluster' Avdyukhin https://github.com/ClusterM
https://github.com/ClusterM/nes2wii

Sega MD 6-buttons query code and documentation:
https://github.com/MickGyver/DaemonBite-Retro-Controllers-USB
https://github.com/jonthysell/SegaController

SMD2Wii modifications:
probotector