Switch Input Proxy

The Switch Input Proxy is a piece of software running on a mini linux computer like the raspberry pi and passes input events of USB HIDs like USB gamepads or trackballs etc. to the Nintendo Switch. It does it by passing the events via the I2C protocol to one or more Atmega32u4 dev boards which act as virtual gamepads to the Nintendo Switch. The Atmega32u4 has to run Switch-I2C-Controller.

I developed this software to be able to connect the Controls of my Atgames Legends Ultimate Arcade Cabinet to the Nintendo Switch.

This project is a prototype and never might leave this state because it does everything I need it to do, at this moment in time at least. It is not very good documented and requires a bit of soldering, bash work and YAML-file editing to set up and configure.

Raspberry PI with two Atmega32u4 virtual controllers

Switch-I2C-Controller

I have to thank Molorius for this great piece of software, it did exactly what I needed for the Switch Input Proxy. Thanks to using I2C it is easy to connect 4 (or even more) gamepads to the Nintendo Switch. Each virtual controller needs one Atmega32u4 dev board and all are connected to the I2C bus of the Raspberry PI. All dev boards need a unique I2C address, please refer to the documentation of the Switch-I2C-Controller Github project for details how to flash it and how to change the address.

Display

I added a small SSD 1306 Oled screen to be able to display the currently active configuration profile. This display is also connected via I2C to the PI.

Configuration

Switch Input Proxy uses two configuration files, the Global Configuration and the Profile Configuration. Both files are merged and support the same values. The Profile Configuration Files have to be placed in a seperate directory and can be switched with a key combination.

Global Config Example

name: Global                        
category: Default                   # Not used
i2c_device: 1                       # ID of the I2C device, 1 is the default on the PI

menu:
  event: BTN_MODE                   # HID event type used as a menu modifier key, find the type name with `evtest`
  device: 
    name: HID 0838:8918             # Name of the HID device, find it with `evtest`
    index: 1                        # Sometimes multiple USB devices have the same name. index: 0 will pick the first device etc.
    bindings:                       # Menu bindings
    - event: ABS_HAT0Y              # HID event type
      state: 1                      # value of the HID event at which the binding will fire
      invoke: NEXT_CONFIG           # menu event which will be fired
    - event: ABS_HAT0Y
      state: -1
      invoke: PREV_CONFIG

Profile Config Example

name: Default                       # Name of the profile, displayed in the display

devices:                            # List of device configurations
  - name: HID 0838:8918             # Name of the HID device, find it with `evtest`
    index: 0                        
    bindings:                       
      - event: ABS_X                # HID event type
        address: 0x51               # I2C address of the Atmega32u4 dev board
        invoke: LX                  # Event invoked on the virtual gamepad, refer to the Switch-I2C-Controller project for a list of events
      - event: ABS_Y
        address: 0x51
        invoke: LY
    relative:                       # Special relative handler to convert Mouse / Trackball input into analog stick output
      - event: REL_X
        invoke: ABS_X
        mult: 1.5
      - event: REL_Y
        invoke: ABS_Y
        mult: 1.5
  
  - name: HID 0838:8918
    index: 1
    bindings:
      - event: BTN_Z
        address: 0x51
        invoke: L
      - event: BTN_TR
        address: 0x51
        invoke: R
      - event: BTN_EAST
        address: 0x51
        invoke: A
      .
      .
      .