NES Controller to Master System/7800

I been watching Videos on YouTube about the Mods, Looks kinda easy if you do it alot of times

One guy was making a switch on the Controller for the Master System & the C64, I wonder if you can do the same with Master System & the 7800 or even Genesis 3 Button Mode..Having a switch for 7800 mode to SMS mode on the Controller

Does anyone here have the Schematic for the Mod?

 

I would love to do something like this. The 7800 joystick is painful to hold for too long.

 

Yes it van be done. I just made a snes adapter today/yesterday. Do note that you need to modify the source code if you want to use the diagram he supplies. Since the controller pinout of the snes and nes are the same i recon it will work.
megadrive/mastersystem:
http://www.raphnet.net/electronique/snes2md/index_en.php
For atari :
http://www.raphnet.net/electronique/snes_to_db9/index_en.php

I was pulling out my hair to figure out what i was doing wrong
In the file main.c change and recompile:
PORTD = 0x00; To PORTD = 0x04; // see note

 

I just want a schematic on how the Mod is done, Pics would be good

It seems no one want to give me the time a day about this, I want to know how to do this