So my wife had her sisters kid over here one night and I let him play super mario bros. Poor guy couldn't use play with the xbox 360 controller lol. So I dug out one of my NES controllers and went to town on it.
Depending on how many buttons u want to add on to the controller depends on what wires u can use. If you want just enough wires for Up, Down, Left, Right, Start, Select, A and B. I personally used an HDMI cable I plan on using the same set up for a SNES controller. You can buy cheap cables (here).
You need to find out which type of wireless xbox 360 controller you have. (Matrix), (CG), and (CG2). I love all of RCDs work.
You the links to find the best points for you. Personally I wanted to make the controller to be to play xbox 360 game and to be able to connect the nes controller to it with out having a problem. I tried to use the back of the board as much as a could but some points where easier on the top.. I am using a CG2 for my mod. Here are some pictures of my wiring. As you see I had to cut some of the rub off for the buttons so the controller was usable for 360 games. You will have to look at the cg2 link to figure out which wire is for what.:p Note you will have to use one wire for ground.
Now I don't have the official nes controller nor do I have any picture of one. This picture is a cloned nes controller I buy off of ebay a few years ago.
First you want to cut the traces around the black blob, disconnecting the traces from the chip. Also cut or desolder the NES wires. Then find out which wire u used for A, B, Back, Start, Up, Down, Left, Right and ground.
This is my finished controller with the HDMI quick connection.
Seeing how the xbox controller work I can help the little guy out.
I am working on a snes controller but do to work, working on my car, jtaging and helping users its not done yet...