Very cheap and quite easy way to connect many non-USB joysticks and gamepads or DIY arcade cabinet controller to almost any machine with USB-port and HID-support. Arduino board with ATmega32u4 chip with help of Joystick-library does all the USB-work.
ATmega32u4 can be easily changed to act as keyboard and/or mouse too. With keyboard device it is easy to make adapter for many mobile devices which don't have gamepad-support out of box. I have tested it with Samsung Galaxy S4 Android phone and Samsung Galaxy Tab 10.1 Android tablet with OTG-USB cable.
If you use Linux and want to get more than 1 controller with one Arduino, check "Linux and more than one controller with one Arduino"-topic in this same page.
Starting point is ATmega32u4 based Arduino board. There is two versions of ATmega32u4, IO-logic with 5V or 3.3V. Many controllers (like basic Atari-controller) doesn't include any logic, so 5V and 3.3V versions are fine. Most of controllers with some logic needs 5V (NES, SNES, Genesis) and some rare ones needs 3.3V (N64/Gamecube) (5V is 16MHz and 3.3V 8MHz, so timings are different and 16MHz code doesn't work for N64/Gamecube with 3.3V version). Make sure that Arduino includes USB-port. There are some versions which doesn't include USB-port and then you have to add USB-connector for it. Arduino Leonardo includes ATmega32u4, but cheapest and smallest ones are named Pro Micro. Arduino Pro Micro and ATmega32u4 are good words to use when searching from Ebay etc. Cheapest starts from about $4.
Arduino IDE works with Windows, OS X and Linux and ARM (beta). If you use small card computer like Rasperry Pi or Orange Pi, you can program adapter even with them (tested with Orange Pi PC and RetrOrangePi 2.0). That way you don't even have to unplug adapter from your emulator/game-platform if you want reprogram adapter.
Some joystick/gamepads uses their own connectors and original connectors can be very pricey. Sometimes you can find extension cord cheaper than plain connector and you can take cable and plug from that.
You can use any IO-pins, but try to avoid pins 0 and 1. They are serial port TX and RX pins and even though they are not used right now, they are handy for debugging and other uses.
In Arduino IDE you have to select board. In my case some reason "Arduino Leonardo" selections works better than "Arduino/Genuino Micro". With Leonardo-setting RX and TX leds are normally off and blinks when data is transfered to/from USB. With Micro-setting LED's are normally on and they blinks to off when data is transferring. Connect now your board ATmega32u4 through USB, the RX and TX leds should blink (if not, try another USB port).
Arduino IDE shows available COM-ports. In most cases it's biggest numbered COM-port. COM-port number can change when you start to upload program first time (COM-port number can be different after joystick-features are enabled). If this happens, just change COM-port and start upload again. When I tested with RetrOrangePi (Armbian Linux), port was `/dev/ttyACM0`. In Windows envoirement, do not use any USB HUB, it may interfere whit the comunication whit ATmega32u4 board.
You can now test your setup. One basic example is "blink". With this board, it doesn't blink, because there is no led in pin 13. Nevertheless you can use it as a test that your IDE and Arduino works. Select `File -> Examples -> 01.Basics -> Blink` and press `Upload` (Arrow to right -symbol top of code windows). If you get no errors, you are good to go.
After extraction check that you have files `%HOMEPATH%\Documents\Arduino\libraries\Joystick2\Joystick2.h and Joystick2.cpp` or `~/Arduino/libraries/Joystick2/Joystick2.h and Joystick2.cpp`.
- You should go now to `Control Panel -> All Control Panel Items > Devices and Printers (some Windows versions in Game Controllers)` and try to find `Arduino Leonardo` device. Right click on `Gamepad controller definitions` > double click in one of the options (1st is the controller one, and the 2nd is the controller two) and you can now test the buttons.
Select your controller by commenting and uncommenting stuff from beginning of source code and give your IO-pin numbers.
Every one uses same button numbering, so if you make multiple adapters for different controllers, you have to teach buttons to emulator/game (or whole emulation system like RetroPie or RetrOrangePi) only once.
#### Konami code
You can also enable or disable Konami-code-shortcut. For now it works only with Genesis 6-button controller (X+Y+Z+UP (or DOWN)), SNES-controller (X+Y+R1+UP (or DOWN)) and PSX-controller (rectangle+circle+triangle+UP (or DOWN)). "UP"-version is normal and "DOWN"-version swaps A and B. Some games demands that not other buttons are pressed before code and that's why only last pressed button can be button which have some function in emulator.
There is simple tutorial in [Tutorial](https://github.com/mcgurk/Arduino-USB-HID-RetroJoystickAdapter/tree/master/Tutorial) folder. I tried to make it as clear as possible, so even if you are not familiar with coding, you may can do modifications to it (example add a button).
On any other MS Windows platforms you may have to install the arduino drivers. To have the last updated ones, just download the file `Windows ZIP file for non admin install` from the page https://www.arduino.cc/en/Main/Software. After the download, unzip the folder. Go to the `Computer` > right click > `Manage > Unknown devices` > right click > `Update software controller > Find on my computer > Search` > and try to find the folder `\arduino-1.6.xx\drivers` inside the folder you unziped before. Click `Next` and Windows should install the driver. Arduino would apper as the name `Arduino Leonardo` inside `Ports (COM and LPT)` with an associated COM port (like `COM9` for example).
Linux usbhid-module doesn't support out of box multiple controllers with one USB without USB-hub-features (I'm not sure about this, but I didn't manage to get multiple /dev/js-devices without this).
Linux problem with multiple controllers are solved with changing VID and PID to something that already has HID_QUIRK_MULTI_INPUT (0x40) activated in kernel.
If you want that less than 16 buttons are shown in joystick-settings, edit Joystick.cpp/Joystick2.cpp/Joystick3.cpp "USAGE_MAXIMUM"-line (0x10 = 16). You may to have create new project after that, because all libraries are not recompiled every time and I don't know how to force full recompile.
Adapter shows as "Arduino Leonardo", but if you want it to show some other name, edit `C:\Program Files (x86)\Arduino\hardware\arduino\avr\boards.txt`. You can even add sub menu to tools-menu by adding these lines (after editing boards.txt, you have to close and reopen Arduino IDE):
Arduino UNO R3 includes ATmega16u2 (along with ATmega328p) and it can be used too, but it needs some extra work (code doesn't work without modifications with UNO):
You can also use Arduino vice versa. You cannot read USB with normal Arduino, but there is shields to make Arduino as USB host. With that you can connect modern USB-joysticks and gamepads to old consoles.
Very handy level converter with 3.3V AMS1117 regulator. Search from Ebay with `Logic Level Converter Module AMS1117 DC 5V to 3.3V`
There is contradictory data about Playstation controller voltages. I have one commercial adapter and it's 5V. I haven't measured official Playstation, but it is probably 3.3V.
Of course Arduino can be used many other ways. Add a PIR motion detector module from Ebay (under $2) and your computer wakes up from sleep when you walk to room. Just read PIR-sensor data pin and if it is 1, send some keyboard button (which normally does nothing) to computer so it wakes up. Or make info-board to your kitchen or hallway wall from old Android tablet and it turns on backlight only when someone goes to kitchen.
