Developers on GB-Link Docs

Firmware Architecture

Wed, 08 Jul 2026 00:00:00 +0000

The GB-Link firmware turns an RP2040 into a USB-to-Game Boy Link Cable adapter, bridging retro hardware to modern web clients.

Hardware & Wiring

Wed, 08 Jul 2026 00:00:00 +0000

The firmware uses the RP2040 PIO to communicate with the Game Boy link port. This page documents pin assignments for DIY builders.

USB Command Protocol

Wed, 08 Jul 2026 00:00:00 +0000

Commands are sent over the WebUSB command endpoint. This reference is for developers building web clients or debugging adapter behavior.

How GBA Online Works

Wed, 08 Jul 2026 00:00:00 +0000

Connecting two Game Boy Advances directly over the internet is impossible due to strict timing requirements. GB-Link solves this with a relay architecture that decouples game data from real-time link timing.

Building from Source

Wed, 08 Jul 2026 00:00:00 +0000

Build the GB-Link firmware locally for development or custom board targets.

Prerequisites

Zephyr SDK
Python 3 with west package manager
CMake and a C/C++ toolchain
Git

The firmware is built against Zephyr 3.7.99. Newer versions should also be compatible.

Porting to Other MCUs

Wed, 08 Jul 2026 00:00:00 +0000

The GB-Link firmware is designed to be largely MCU-agnostic thanks to Zephyr RTOS. The original Celio project targeted STM32F07; migrating to RP2040 required only minimal to moderate effort.

Contributing

Wed, 08 Jul 2026 00:00:00 +0000

GB-Link is an open-source project. Contributions are welcome across firmware, web clients, hardware, and documentation.

Repositories

Component	Repository	License
Firmware	GB-Link/GBLink-Firmware	GPL-3.0
Web clients	GB-Link organization on GitHub	GPL-3.0
Hardware (PCB)	KiCad designs (CERN-OHL-S v2, releasing with V2 shipment)	CERN-OHL-S v2
Documentation	This site	—

How to contribute

Firmware

Fork GBLink-Firmware
Create a feature branch
Make your changes and test on hardware
Open a pull request with a clear description

See Building from Source for the development setup.