Neo Geo controller for Nintendo NES and Famicom

adapter that allows one to use unmodded controller for NES and Famicom system

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Want to use nice Neo Geo controller on your NES or Famicom? This adapter allows the use of standard Neo Geo controller without damaging the expensive controller or altering the console. And it can be used with either NES or Famicom. Official Famicom and Twin Famicom has 15 pins expansion port that supports this adapter. Most Famicom clones do not have this, you will have to figure out the wiring for 9 pin DSUB ports.

If you choose to include wires and connectors for both NES and Famicom consoles, be sure to unplug cables from one console before powering on the other console, or damage could occur.

BOM: (all parts are through hole for easier soldering)

If you do not wish to have rapid fire circuit, you can omit the "optional rapid fire circuit"  listed below. Button C and D will not function at all.

2 player board
* C1-C4 0.1uF
* R1-R16, R19, R20, R23, R24 1K 1/4w
* IC1, IC2 4021N DIP IC
* 2x 15 pin DSUB MALE PCB mount
* 2x NES and/or 1x Neo Geo/Atari 5200 controller extension cable 

optional rapid fire circuit

* C5-C8 1uF
* R17, R18, R21, R22 27K 1/4w
* IC3, IC4 74HCT02N DIP IC (some general TTL may not work correctly, needs to be a CMOS friendly version)

1 player board

* C1-C2 0.1uF
* R1-R10 1k 1/4w
* IC1 4021
* 15 pin DSUB MALE PCB mount
* 1x NES and/or 1x Neo Geo/Atari 5200 controller extension cable

optional rapid fire circuit

* C3-C4 1uF
* R11-R12 27k 1/4w
* IC2 74HCT02

Controller button mapping are: Neo Geo A to NES B, Neo Geo B to NES A, Neo Geo C to NES turbo B, and Neo Geo D to NES turbo A. I've included pictures of 3 Neo Geo controllers and the button mapping. A and B may seems backward but this is how NES and Famicom controller is laid: B and A

This adapter will not work with Neo Geo mini controller!!

Neo Geo to NES adapter 2P

Gerber files for most PCB fab shops. This is for 2 players version

x-zip-compressed - 336.29 kB - 05/16/2022 at 03:37


1P Neo Geo to NES adapter 1P

Gerber files for most PCB fab shops. This is for 1 player version

x-zip-compressed - 213.70 kB - 05/16/2022 at 03:37


  • 20 × 1k ohm resistor 1/4 w (1/8w will work) pullup resistors, need 10 for 1P version
  • 4 × 27k ohm resistor 1/4w (1/8w will work for auto fire timing, need 2 for 1P version
  • 4 × 0.1uF ceramic capacitor decoupling, need 2 for 1P version
  • 4 × 1uF ceramic capacitor for auto fire timing, need 2 for 1P version
  • 2 × 4021N integrated circuit encoding controller for Nintendo console, need only 1 for 1P version

View all 7 components

  • Final revision

    killua05/16/2022 at 03:51 0 comments

    Final revision, PCB was made slightly shorter so those 15 pin male connector would stick out for easier mounting into PCB boxes.  Added missing pullup resistors to button C and D line, this could have caused intermittency rapid firing without pressing any button if the rapid fire circuit was assembled.  If you got the older version of the board without the pullup resistor, solder one side of each resistor to pin 2 and one to pin 12, and connect the other side of resistors to VCC source like pin 14 or the nearby capacitor.

    To do: SMD version for smaller board size maybe?

View project log

  • 1
    Fairly straightforward

    Requirement: multi-meter (in OHMs setting), soldering iron, wire cutter, and wire strippers, and have some soldering experience. I used all larger through hole components for easier soldering. If you do not have the equipment or the soldering experience, I find a 6-pack of quality beer would be enough to get a friend to help with the project.

    Assemble parts by matching the parts from bill of material (BOM) with the silkscreen and solder them on.

    For NES cable, I'd use the NES extension cable and cut off one end, be sure the plug that goes into NES deck has enough length of wires that you can work with. Strip the exposed wires, use meter to find which pin goes to which wire. The top silkscreen in the middle of the PCB has handy pinout guide.  Cut off or tape off unneeded wires (make sure no stray strand of wire would touch anything) or use heatshrink over it.  Solder wires according to the pinout, one cable to NES1 on top, and second cable to NES2 on bottom.

    For Famicom consoles, I would use Neo Geo or Atari 5200 extension cable and cut off leaving enough at female end to work with.  Using the handy pinout guide, find which wire goes to which pins, be aware the female end pin numbering is reverse of male pin numbering. To make checking with a meter easier, I would use the 15 pin male connector before it's soldered on the PCB and use that to probe the pins to wires. When you find all 7 wires you need, cut off the unused wires and tape it off or use heatshrink to seal it in. Make sure there's no stray strand of wire sticking out.

    Before plugging the adapter board into NES or Famicom console,  using meter check the resistance between VCC and GND to ensure there's no short.

    Finished 2P PCB is 3.40 x 3.20 inches (86.5 x 81.4mm) and 1P PCB is 3.40 x 1.85 inches (86.5 x 47.1mm). It should fit most project boxes whose inside dimension is bigger. I intended to use plastic standoff and glue one end to the bottom of the box after I make the necessary cutout for Neo Geo controller port on one side and small opening for the cable(s) on other side. The board can then be screwed or snapped into the standoff.

    Controller doesn't work at all? Check that you wired the cable for NES or Famicom correctly, use an IC tester on 4021 if you can. test Neo Geo controller to ensure it is not defective. Check for solder shorts, incomplete or cold solder, and for stray solder blob or bits of wire on the PCB.

    Controller works but rapid fire doesn't work? Make sure that 7402 is CMOS friendly version. If you have access to logic probe, check pin 2 and 12 to see if button C and D is getting through, then 1 and 13 to see if you got pulsed output when the button is pressed. If there's no pulse or only 1 side, try a different 7402. If another 7402 does not change, probably faulty capacitor?

    For Famicom only: not all games will support extra controllers on expansion port.  Some games will treat the 2 extra controller as player 1 and 2, same as built in controllers. Some games like Twinbee will treat player 1 and 2 in expansion port as player 3 and 4.  If you are playing NES games on Famicom with a cartridge adapter or with a flash cart, 3-4 players NES games will not work with expansion port as they were coded differently to use external 4 players adapter.

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