SNES Userport Adapter

SNES Controller to CBM Userport Adapter

This repository contains the KiCad project and Gerber files for an adapter that allows to connect a SNES controller to the Userport of many Commodore 8-bit computers like the C64, C128, PET, Plus/4 and VIC-20.

This adapter was developed for the game "PETSCII Robots" by The 8-bit Guy. The official adapter is available for purchase from Texelec. When you live in North America, I recommend that you buy it there instead of using this clone. This repository is only for persons living in countries where shipping from North America and taxes are prohibitively expensive.

The Adapter is also supported by some other games. See the Texelec web site for more information. You can also use the C64 program Joyride to test the adapter.

[!WARNING] This adapter works reliable with original SNES controllers, but it does not work with certain third-party/aftermarket controllers! See the section "When your controller does not work" below for more information. Use this adapter at your own risk!

Ordering the PCB

The subdirectory "gerber-files" contains a Zip file you can use to order the PCB from PCB manufacturers like PCBWay or JLCPCB. Simply upload the Zip on their web page. I recommend to order the standard PCB thickness of 1.6mm and HASL finishing.

Building the Adapter

Bill of Materials

• 1x SNES Controller Socket Right Angle.

  Search for "90 degree female 7 Pin SNES socket" on AliExpress.

• 1x 24 Pin Edge Connector 3.96mm pitch.

  Search for "24 Pin Edge Connector 3.96mm" on AliExpress. There are two types of connectors, one with pins, and one with soldering lugs. They both work, but I recommend the ones with pins.

• (Optional) 1x 3x1 Male Pin Header Through Hole Right Angle 2.54mm pitch.

  This is only needed when you want to build the external power supply for PETs without 5V on the Userport.

• (Optional) 1x Jumper 2.54mm pitch.

  Also for the external power supply.

• (Optional) 1x 50-500 Ohm Resistor Through Hole 0207 size.

  This is only needed when using the adapter on an old PET that does not have a speaker. In that case, you can fit the adapter with an audio jack for sound output.

• (Optional) 1x 3.5mm Audio Jack (Ledino KB 3 SPRS or Shenzhen Intech PJ-324)

  Also for sound output on old PETs.

Soldering the Power Supply

The first PET computers do not have +5V on pin 2 of the Userport. For that reason, the adapter supports a connector for an external power supply.

When you do not plan to use the adapter on such a PET, you can simply close the jumper on the bottom of the PCB with a blob of solder. This will supply the SNES controller with +5V from pin 2 of the Userport.

When you want to use the option to use an external power supply, you can solder the 3x1 male pin header on the top side of the PCB. To use the +5V provided by pin 2 of the Userport, simply put a jumper on pins 1 and 2 of the pin header. To use an external power supply, connect +5V to pin 2 and ground to pin 3 by using female Dupont connectors. You can also use the tape port as an external power supply, simply connect pin 2 or B of the tape port to pin 2 of the pin header (no need to connect ground in this case).

Soldering the Audio Interface

The first PETs did not have any sound output. A popular workaround is to connect active speakers to pin M of the Userport (search for "PET CB2 sound" on the Internet). This is also supported by the adapter. Simply solder a resistor (50-500 Ohms) and an audio jack to the PCB. This of course is not needed on other Commodore machines and completely optional. It is also currently untested, so please drop me note when you successfully use this option on a PET.

Unfortunately, getting the audio jack into the PCB is extremly fiddly. Even though it is an official KiCad footprint, the holes seem to be a little bit to small.

Soldering the Userport Edge Connector

Before soldering the Userport connector, you have to bend the pins a little bit inwards so that they touch the surface of the PCB. Carefully push down the connector on a hard surface to bend the pins uniformly on both sides.

When you are satisfied with the result, slide the connector onto the PCB. Doing that can be a little bit fiddly, be careful not to bend any pins sideways!

Solder the edge connector into place. You'll need a lot of solder and heat.

Soldering the SNES Controller Socket

When you order your SNES controller socket, you'll probably get a socket where the pins point in the wrong direction. That is not a problem, the pins are only sticked into the socket and can be rotated into the other direction. By using a pair of pliers, carefully pull out the pins a little bit, rotate them by 180 degrees, and push them back.

Solder the socket into place. You'll need a lot of heat, especially for the ground pin (that's the outermost pin on the round side).

3D-Printing a Case

In the subdirectory "case" of this repository there are STL files you can use to print a case for the adapter on your 3D printer. You need a self-tapping flat-headed M3 Phillips screw. Mine had a length of 12mm, but any length between 10mm and 16mm should work.

There are two variants of the case, one for the PET version with holes for the power supply and the audio connector, and one closed version in case you did not populate the PET-specific parts of the PCB.

Using the Adapter in your Software

The SNES controller actually just consists of a 16-bit shift register (two 8-bit shift registers on older versions). The 12 buttons are connected to the parallel inputs of the shift register, and their state gets serially transmitted to the computer. There are two lines from the computer to the controller called "Latch" and "Clock", and one line from the controller to the computer called "Data". When the computer toggles "Latch", the shift register copies the state of the 12 buttons into its internal register. When the computer toggles "Clock", the shift register sends the contents of its internal register serially over "Data" to the computer. The first 12 bits correspond to the 12 buttons, and the last 4 bits are unused. Even though it might be tempting to ignore the last 4 bits and save some time, I strongly recommend to read the full 16 bits, otherwise your software might not work with certain third-party controllers. See the section "When your controller does not work" below for more information.

There is a small example assembler programm called snes_userport.asm in this repository which demonstrates how to correctly read the SNES controller on PET, VIC-20, Plus/4, C64 and C128 machines. Use 64tass to compile the example, the command lines for the different target systems are documented at the top of the source code. Feel free to integrate this example code into your own software!

There is a nice blog post by Michael Steil that explains how the SNES controller works more in detail. He also provides a software example, but keep in mind that he is using different pins of the Userport, so you have to adjust his example when using it with this adapter.

The source code of PETSCII Robots is also available on Github. Search for the subroutine called "SNES_CONTROLER_READ" to see how The 8-bit Guy reads the button states. But keep in mind that PETSCII Robots incorrectly only reads 12 bits from the SNES controller, which does not work with certain third-party/after-market controllers.

Finally, there is the source code of Joyride available on Github. Starting with version 1.7, Joyride correctly reads the full 16 bits from the SNES controller.

When your controller does not work

This adapter works reliable with original SNES controllers, but there are certain third-party/aftermarket controllers which do not work. Investigation revealed that this is not an issue with the adapter, but with the controllers. These controllers do not behave correctly, they do not work when software does not read the full 16 bits from the shift register, but only the first 12 bits which are actually needed to cover all buttons of the SNES controller. You can check if your controller is also affected by this problem by using the free joystick test program Joyride. Starting with version 1.7, Joyride reads the full 16 bits, so it should work correctly with all controllers out there.

Unfortunately most software using the SNES Userport adapter incorrectly reads only 12 bits, most prominently PETSCII Robots itself. It is easy to fix this problem, but this has to be done by the respective software developers. Since the source code of PETSCII Robots is available, I have prepared patched versions for all systems in the folder PETSCIIRobots-patched of this repository:

• c64robots.v1.2: Patched C64 version (v1.2). Replace the file "c64robots" in the disk image with this file.
• c64robots.v1.3: Patched C64 version (v1.3). Replace the file "c64robots" in the disk image with this file.
• game-64x: Patched C64 REU version. Replace the file "game-64x" in the disk image with this file.
• common-128: Patched C128 version. Replace the file "common-128" in the disk image with this file.
• plus4gfx: Patched Plus/4 version. Replace the file "plus4gfx" in the disk image with this file.
• vicrobots: Patched VIC-20 version. Replace the file "vicrobots" in the disk image with this file.
• petrobots: Patched PET version. Replace the file "petrobots" in the disk image with this file.
• petrobots.gfx: Patched PET version with custom character set. Replace the file "petrobots" in the disk image with this file.

Please keep in mind that most of these patched versions are untested, so use at your own risk!

License

SNES Controller to CBM Userport Adapter (c) by Patrick Dähne

SNES Controller to CBM Userport Adapter is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

You should have received a copy of the license along with this work. If not, see https://creativecommons.org/licenses/by-nc-sa/4.0/.