fightstick

An open-source USB fight stick built around the stm32f0-usbd-devboard, with a 3D-printable enclosure and arcade-grade controls.

Overview

fightstick is a USB gamepad designed for fighting games on Linux and MiSTer FPGA. It uses a stm32f0-usbd-devboard as its controller, a Sanwa JLF-TP-8YT joystick lever for directional input, eight Sanwa OBSF-30 game buttons, and four Sanwa OBSF-24 control buttons. The enclosure is fully 3D-printable.

The firmware is bare-metal C targeting the STM32F042K4 microcontroller, running at 48 MHz from the internal HSI48 oscillator. It presents itself as a standard USB HID gamepad with a 1 ms polling interval, requiring no custom drivers.

Key highlights

• Standard USB HID gamepad -- no drivers required, works out of the box on Linux and MiSTer FPGA
• 1 ms polling interval -- tested at 1.39 ms average button latency with a Gamepad Latency Tester
• Sanwa arcade parts -- JLF-TP-8YT joystick lever, OBSF-30 game buttons, and OBSF-24 control buttons
• 3D-printable enclosure -- OpenSCAD parametric models for the panel and base plate
• USB DFU firmware updates -- enter DFU mode by pressing two buttons at startup, or flash via ST-Link
• Bare-metal firmware -- no HAL, no RTOS, built with cmake-cmsis-stm32 and usbd-fs-stm32
• Open source -- hardware licensed under CERN-OHL-S-2.0, firmware under BSD-3-Clause

How it works

The stm32f0-usbd-devboard reads 16 GPIO inputs (4 joystick directions and 12 buttons) using internal pull-up resistors. Each button and joystick microswitch connects its corresponding GPIO pin to ground. The firmware runs a USB HID interrupt IN endpoint that sends a 3-byte report containing a 2-axis digital joystick (X/Y values of -1, 0, or 1) and 12 button states at up to 1000 Hz. An on-board LED indicates USB enumeration status.

Explore further

• Assembly -- parts list, wiring, and 3D-printed enclosure
• Firmware -- building, flashing, architecture, and USB HID protocol
• Source code -- GitHub repository
• stm32f0-usbd-devboard -- development board documentation