Convincing a modern game console such as a PlayStation 4 or the Nintendo Switch that a microcontroller is a legitimate gamepad is much trickier than typical USB HID keyboard and mouse techniques we use on computers. This is where the GP2040-CE firmware comes in.

GP2040-CE is an open source gamepad firmware that's compatible with PC, PS3/PS4, Nintendo Switch, Xbox, and more. It runs on a number of microcontrollers that use the RP2040 chip, such as Pico, KB2040 Kee Boar, and more.

Flash the Pico with a drag-and-drop .uf2 file and then customize settings with a web editor.

Your Pico reboots as a generic controller, which may work on a Windows PC or Xbox right out of the gate, but you'll want to reconfigure it as a Switch controller with specific behaviors. To do this, we'll launch the built-in Web Configurator!

Settings

You can now update the controller settings. Click on the Settings menu item and then switch the Input Mode to Nintendo Switch.

To do the Auto Spin hack we need to be able to automatically press the left analog stick. Change the D-Pad Mode to Left Analog.

Then, scroll to the bottom of the settings page and press Save.

Switch Button Test

This is a great time to test the controller on your Switch to make sure basic button presses are working.

The pinout diagram below shows the default GPIO-pin to button mapping.

Plug the Pico into your switch with a known good USB-C to Micro-B data and power cable.

You can now use a jumper wire to short any mapped GPIO pin to ground -- those button presses will register on the Switch! 

Auto Spin Macro

The secret sauce for our Pokéball is the Macro Settings section of the configurator. Click the Configuration menu item and then click on Macro.

• click the Enabled button to turn on macro support
• you need to assign a free GPIO pin to be the Macro button (see pinout chart above), set this to 22
• click the Activated button next to the first macro slot
• for clarity, name the macro Label spin
• Turn off Interruptible so that the Auto Spin will run without interruption
• Leave Exclusive on so other controls won't join the mix by accident if buttons are pressed
• you can turn on Show Frames if you prefer frame counts for button press timings (vs. milliseconds)
• change the mode dropdown from Press to Hold Repeat -- this will loop the macro endlessly as long as the button is held
• Click the green + button to add a macro line (you can add up to 50 lines!) set it as shown above. This will press Left for 6 frames
• Repeat the above step three more times to add Up, Right, and Down events
• Click the Save button at the bottom of the page to write the configuration to the Pico

Next, you'll house the device in a Pokéball.