Combine an original NES controller, USB keyboard, wire and tact switches into a USB NES controller suitable for use with NES and arcade emulators. The basic idea is that the keyboards controller unit is installed in the NES controller housing. The original buttons activate tact switches that are wired to the keyboard controller. When the NES controllers buttons are activated, they're registered by your computer as a key press.
- Nintendo NES controller
- USB Keyboard
- 8 Tact switches
- Light duty wire. preferably coloured to make life easier when soldering.
- Soldering equipment
- Dremel (rotary tool) with cutting bit
- Small files
- Hot glue gun
Disassemble your keyboard. They tend to have half a bazillion screws on the back that need to be removed. A flat head screwdriver helps to pry the keyboard open. Although most keyboards differ slightly they usually contain two sheets of plastic with traces that create the key matrix. These sheets connect to the contacts on the keyboard controller. When a key is pressed, it connects the contacts on both sheets which closes the circuit and registers a key press. We're going to solder wire to the contacts on the keyboard controller however be sure to keep the two sheets as they will provide valuable information on how to wire it all up.
Remove the keyboard controller from the keyboard housing. The contacts on my controller were covered with a protective coating that prevents me from soldering to them. After taking some time to gently scrape the coating off with a scalpel, the contacts were revealed. I had to clip the green LEDs off the controller also as they protruded too much.
A NES controller has eight inputs (up, right, down, left, select, start, b, a) therefore we need to prepare the keyboard controller to accomodate eight inputs. After looking at the key matrix for my keyboard controller, I can see that the top sheet connects to the first 8 contacts (group A) and the bottom sheet connects to the remaining contacts (group B). Yours may not be the same therefore you should examine which contacts each sheet connects to. This shows that key presses are registered when a connection is made between one of the first 8 contacts and the remaining contacts.
We need to figure out which key presses are registered by connecting the different contacts. You can examine the traces on the key matrix, however considering a NES controller only has 8 buttons. I found it just as easy to connect the controller to a computer, fire up notepad and connect the different contacts with a paperclip. You want to find pin combinations that produce key presses that aren't usually assigned to hot keys or other configuration options. This makes the most ideal inputs the 26 alphabet characters, directional inputs, enter, space etc. Inputs such as the function keys or numbers are usually assigned to hot keys in most emulators and will require additional configuration to make everything play nice. Some of the less common inputs like ~ are not recognised by some emulators also therefore it's best to find all safe inputs for smooth results.
Test each contact by holding one end of a paperclip or wire on a contact in group A and touching the other end on the contacts in group B. When a combination provides a useful input, note down which contacts you connected and continue. Ideally you want to have one button per eight of group A's inputs (to prevent key ghosting) however you will likely find that two or three of the contacts won't produce any useful inputs. To remedy this I used a single contact for two switches (see green and orange wires in images) and will connect them to switches that would never be pressed simultaneously such as up/down and left/right.
Now you've determined eight separate useful button inputs, it's time to connect the wiring. Clip yourself 15cm lengths of wire to attach to the controller. I would recommend using coloured wire if possible as you can colour code each button input pair. You want to have a coloured wire connected on group A matched to the same coloured wire(s) on group B. This way you can just connect each coloured wire pair to the switches later on to make life a bit easier. You can also mark or tag the wire but I would strongly recommend labeling them in some fashion so you can make the correct connections later.
I've found the best method is to pre-tin each wire and all the contacts on the controller with some solder then fuse them together with a little heat from your iron. Once you've connected all the wires, connect the controller to a computer and test each input in notepad by touching the end of each wire pair together. When you touch the ends of each pair, a key press should be registered. If not, check you haven't bridged any of the contacts or connected the wiring incorrectly.
Disassemble the NES controller by removing the six screws in the back. Remove all the parts and put them aside for now. I had to cut out a few sections in the controller housing to allow all the parts to fit (see images). The NES controllers PCB had the large portion without the buttons removed with a dremel to provide the bulk of the space for the keyboard controller.
We're going to install tact switches where the current button contacts are located. This will activate the tact switch when a button is pressed on the NES controller. Drill small pilot holes in the center of each button to ensure an accurate location. Drill them out to a larger size and file each hole to allow a tact switch to fit.
The depth of the tact switch alters the feel of the controller. Install the switches level with the PCB and the controller will have a softer mushier feel. Install the switches so they protrude from the PCB and the buttons will be firmer. I chose to allow them to protrude around 1mm. Install all of your tact switches and add some hot glue to hold them in place.
Insert the NES controllers buttons and spacers. Place the PCB onto its original location. As there were a few things removed from the PCB and housing, it doesn't sit as firmly as I would like. You may need to add a bit of hot glue to secure the PCB however ensure you don't block the controller from closing. Install the keyboard controller with the wiring facing towards the switches. Route the USB cable through the original slot and secure the lot with a few spots of hot glue. You're now ready to connect each input wire pair to the switches.
Solder each of your input wires to the switches. Most of the pairs consist of one wire in group A and B. These connect to either side of the switch. This is where using coloured wires comes in handy as I can easily see each pair. I had used contacts from group A for two switches (up/down and left/right). If you've connected a contact to two buttons, they have to be buttons on the NES controller that are not pressed simultaneously or you may have issues with ghosting. Once you've made the connections, connect the controller to a computer and test that each button on the NES controller produces a key press. If all is good, add some additional hot glue for strength.
Put it all back together and you're holding a USB NES controller. Plug it in, configure it for your emulator and have some good times. I've attempted to provide the best explanation of these steps but I'm happy to try and help in the comments if something's unclear. I've enjoyed paying a visit to some Nintendo classics and this controller provides an experience that's as close as you'll get to the real thing without wiping the dust off your old console.