This project was used as a reference.
This is my USB firmware for the WeAct Studio Blackpill and its many clones. This is a device that reads the input of a SNES/SFC controller and translates it to a USB gamepad, allowing the user to use it as if it was a USB joypad. It is based on the mouse example provided by ST by modifying the usbd_hid_core.c and overriding the original file at $STM_SRC_DIR/Libraries/STM32_USB_Device_Library/Class/hid/usbd_hid_core.c. Since it is using the HID class sources there is no need for extra drivers when running OS X / Linux. This document was used as a technical reference to talk to the controller.
The firmware was adapted for STM32F401CC devices running on a 25 MHz crystal oscillator. It is a suboptimal choice to get solid USB clocks, but when they sell you a board with it you already have no choice and it's better than tossing it into the garbage. Don't let your USB go to waste if you're unlucky and have such a board.
Tested with an original, first-revision Super Famicom controller.
| Controller Pin | GPIO Port, Pin |
|---|---|
| CLOCK | GPIOC, 13 |
| LATCH | GPIOC, 14 |
| DATA | GPIOC, 15 |
The MCU's internal pull down resistors are used to protect the signal integrity. The MCU will poll the controller to obtain a bitmask, invert it and pass it to the HID report.
Download and install the following software for your platform
- The gcc-arm-none-eabi toolchain.
- openOCD or dfu-util depending on your upload method choice.
- st-link (optional)
- The stm32f4 firmware - Download from ST
- Specify the folder of the firmware in the Makefile and run make.
- Upload the resuling binary to the board using openOCD, dfu-util or st-link.
Simply connect the SNES controller to the board and plug the included USB-C port to your computer. The USB Type C port both supplies the board with power and acts as a HID joypad.