fixmylife/Mods/Game Boy Advance · GB-Link adapter

DIY hardware · Game Boy Advance

GB-Link adapter

A Raspberry Pi Pico + a link cable, about $10 in parts

A Raspberry Pi Pico wired to a Game Boy link cable becomes a USB adapter for your GBA. With the free GB-Link firmware and a browser, it can send games to a GBA with no cartridge, trade Pokémon online, play Advance Wars over the internet and more. The screen above is our own test program, sent over the cable.

A Game Boy Advance screen reading HACKED BY FIXMYLIFE, sent over the link cable

Build it in three steps

You need a Raspberry Pi Pico (RP2040), a Game Boy Color link cable, a soldering iron and a multimeter.

  1. 1

    Wire the cable to the Pico

    Cut one plug off the link cable and solder its six wires plus the shield to the Pico (see Wiring below).

  2. 2

    Flash the firmware

    Hold BOOTSEL while plugging the Pico in, then copy the gblink .uf2 file from the releases page onto the RPI-RP2 drive.

  3. 3

    Send something to the GBA

    Use the multiboot sender on this page (in Chrome or Edge) with our test screen, and turn on the GBA with no cartridge in.

On this page

PartsWiringFirmwareTest itChip GateWhat it can doLinks

01 · What you need

Parts

PartNotes
Raspberry Pi Pico (RP2040)The original 2020 Pico or a Pico W. An RP2040-Zero also works and has the status LED built in. A Pico 2 (RP2350) does not work.
Game Boy Color link cableA generic GBC-style cable with six wires. The multiboot tool needs this type, not the GBA cable with the grey hub.
MultimeterWith a continuity (beep) mode, to find out which wire is which.
Soldering iron and heat-shrinkTo join the wires to the Pico and cover each joint.

GBA only, unless you add a level shifter

The GBA's link port runs at 3.3V, the same as the Pico, so it can be wired directly. An original Game Boy or Game Boy Color uses 5V, which can damage the Pico. For those, add a bi-directional level shifter, as on the GB-Link USB DIY board.

02 · Soldering

Wiring

Looking at the end of a link cable plug, the top row is pins 1 3 5 and the bottom row is 2 4 6. Wire colours are not standard, so find yours with a multimeter: beep each pin in the plug you cut off against the bare wire ends, and write the colours down.

Plug pinSignalPico pin
5SC (clock)GP0 (pin 1)
3SIGP1 (pin 2)
2SOGP2 (pin 4)
4SDGP3 (pin 5)
1SD2GP4 (pin 6)
6GNDGND (pin 3)
ShellShieldGND

This is the wiring used by the GB-Link firmware and the GB-Link USB DIY board. The firmware reads on GP1 and sends on GP2, and GBC cables cross the two data wires inside. Depending on which plug you numbered, they can end up the wrong way round, so if nothing works, swap the wires on GP1 and GP2 first.

Our cable, for example

Blue on GP0, brown on GP1, green on GP2, yellow on GP3, orange on GP4, and red and black on GND. We first had brown and green the other way round, and swapping them was the fix.

Red can be ground

On our cable the red wire was ground. To find ground for sure, plug the cable into the GBA (turned off), touch one probe to the battery minus (–) spring and beep the wires. Never connect 3.3V or 5V to plug pin 1.

Add a reset button

A push button between RUN (pin 30) and GND (pin 28) restarts the Pico without unplugging it. Hold BOOTSEL and tap it to get back into flashing mode.

03 · Software

Flash the firmware

  1. 1

    Download the firmware

    Get gblink.v2.2.3.uf2 (or newer) from the GB-Link releases page.

  2. 2

    Put the Pico in flashing mode

    Hold BOOTSEL on the Pico while plugging it into your computer. A drive called RPI-RP2 appears.

  3. 3

    Copy the file

    Drag the .uf2 onto the drive. The Pico restarts by itself and shows up as GBLink USB.

04 · First boot

Put something on the GBA screen

The GBA can start a small program sent over the link cable when no cartridge is inserted. This is called multiboot. Our test screen is a 75 KB program that shows HACKED BY FIXMYLIFE. It's a quick way to prove your wiring works.

  1. 1

    Open this page in Chrome or Edge

    On a computer or an Android phone. Other browsers can't talk to USB devices.

  2. 2

    Pick a program and connect

    Click Or use our test screen below (or drop in your own .gba file), then click Connect USB and choose GBLink USB.

  3. 3

    Send it

    Take the cartridge out of the GBA and connect the cable. Click Send to GBA, then turn the GBA on. The screen appears after a few seconds.

1 · Program

2 · Adapter

Not connected

3 · Log

Pick a program, connect the adapter, then press Send.

Based on GB-Link Multiboot Web (GPL-3.0).

Hacked by FixMyLife test screenOur own GBA multiboot program, to keep or send with another tool. It only draws a picture and changes nothing on the console.hacked_by_fixmylife_mb.gba · 75 KBDownload

If it doesn't work

The log saysWhat it means
got 0xffffffff on every pollNothing is coming back from the GBA. Swap the wires on GP1 and GP2, check the ground wire, and make sure no cartridge is inserted.
Nothing in the device listThe Pico isn't running the firmware. Flash the .uf2 again, and use Chrome or Edge.
Transfer starts, then failsA loose plug or solder joint. Push the plugs in fully and check each joint.

05 · Mega Man Battle Network

Use it as a Battle Chip Gate

The adapter can pretend to be the Battle Chip Gate accessory, so you can insert chips from this page instead of plastic chips. The list below has the Navi chips for Rockman EXE 4.5: Real Operation; any other chip works by typing its ID.

Needs firmware v2.2.8 or newer

Chip Gate mode is in the GB-Link v2.2.8 pre-release. Flash gblink.v2.2.8.uf2 from the releases page the same way as before.

  1. 1

    Connect before turning on the GBA

    Pick the gate for your game, click Connect USB and choose GBLink USB. Then turn on (or reset) the GBA with the game in.

  2. 2

    Insert a chip

    When the game sees the gate, enter a battle and click a chip. To use another, just click it; the old chip is pulled out first so the game notices the new one.

1 · Gate

2 · Adapter

Not connected

3 · Insert a chip

4 · Log

Pick a gate, connect the adapter, then turn on the GBA.

06 · Next

What else it can do

Everything runs in the browser from the GB-Link launcher. Put the game cartridge in and pick its tool; only multiboot needs the cartridge out.

Gen 3

Pokémon trades online

Trade and battle with other people in Ruby, Sapphire, Emerald, FireRed and LeafGreen.

Pokémon

Events and Wonder Cards

Receive old Mystery Gift events and event Pokémon on a real cartridge.

1 and 2

Advance Wars online

Play head-to-head over the internet on real hardware.

Emulation

e-Reader

Send e-Reader card data to your GBA without the e-Reader or the cards.

Homebrew

Multiboot

Send your own GBA programs (up to 256 KB). Butano is an easy way to start.

Needs a level shifter

Game Boy Printer

Save Game Boy Camera photos and other prints as image files.

07 · Downloads

Links

  • GB-Link firmware releasesgithub.com/GB-Link/GBLink-Firmware/releases/latestThe gblink .uf2 file to flash onto the Pico
  • GB-Link launcherlauncher.gblink.ioEvery game and tool that works with the adapter
  • GB-Link USB Multibootmultiboot.gblink.ioSends .gba files to a GBA with no cartridge
  • GB-Link firmwaregithub.com/GB-Link/GBLink-FirmwareSource code and the USB command list
  • GB-Link USB DIY boardgithub.com/GB-Link/GB-Link-USB-DIYA ready-made PCB with a level shifter for Game Boy and Game Boy Color
  • Pico Zero link boardgithub.com/weimanc/game-boy-zero-link-boardA smaller PCB for the RP2040-Zero

Last checked: 2026-11-04 · GB-Link firmware v2.2.8

GB-Link is free, open-source firmware by its own authors; this guide only shows how to wire and use it. Only send games and programs you're allowed to use. Nintendo, Game Boy, Game Boy Advance and Pokémon are trademarks of their owners. This project is not affiliated with Nintendo.

© 2026 fixmylife · All pages