PixelPoach

A homebrew tool for Game Boy Advance hardware that can send and receive photos from a real Game Boy Camera.

By Scott Ratchford — scottratchford.com

Where it came from

PixelPoach is the inverse of GBScribe, my homebrew word processor and pixel-art tool for Game Boy Advance hardware that prints to a real Game Boy Printer. GBScribe drives the printer by bit-banging the link port in general-purpose GPIO mode. Its printer layer was extracted into AdvancePrint. PixelPoach extends that same link driver in the other direction, using the camera's LINK/TRANSFER protocol and accepting the photos it sends.

Why it's a GBA app, not a Game Boy Color app

The target hardware is a Game Boy Advance running an EZ-Flash Omega Definitive Edition. That cart runs .gb/.gbc files through Goomba Color, a software emulator on the GBA's ARM CPU, which has no serial link implementation. This prevents the use of accessories like the printer.

This requires PixelPoach to be a native GBA application. It communicates with the Game Boy Camera by bit-banging the link port in general-purpose GPIO mode.

GBA ── link port (GPIO mode) ── GBC/GB-Pocket link cable ── Game Boy Camera

Quick start

1. Build the ROM and copy it to the flash cart's SD card.
2. Boot PixelPoach on the GBA and connect the GBA to the GBC running the Game Boy Camera with the link cable.
3. To pull a photo, pick Receive photo on the GBA, then on the camera press the SELECT button to open the menu, move UP to LINK and press A, move DOWN to TRANSFER and press A, then choose SEND and pick the picture.
4. To put it back, pick Send photo on the GBA, then on the camera press SELECT, move UP to LINK and press A, move DOWN to TRANSFER and press A, then choose RECEIVE. This does not delete the photo from the save file.
5. Power off, pull PixelPoach.sav off the SD card, and run the extractor to turn the photos into images (see below).

Extracting photos

PixelPoach stores photos in a Game Boy Camera-format .sav. Pull the .sav off the flash cart's SD card, then convert the photos to images with the bundled extractor:

python tools/extract_sav.py PixelPoach.sav            # -> photos/photo_01.png, ...
python tools/extract_sav.py PixelPoach.sav -o out --green --scale 6

• -o, --outdir — where to write the images (default photos)
• -s, --scale — integer upscale factor (default 4)
• --green — use the classic Game Boy green palette instead of grayscale

PNG output needs Pillow (pip install pillow); without it the script writes 24-bit BMP files, which any image viewer opens. Each photo is 128×112, written as photo_NN in the order the camera lists them.

Features

• Receives a photo the camera sends over LINK/TRANSFER and stores it in a camera-format .sav on the flash cart (the same 128 KB layout the camera's own SRAM uses)
• Sends a stored photo back, so a trade that would normally delete the source leaves the camera holding the original
• Browse and view stored photos on the GBA screen, in the camera's 128×112 2 bpp format
• The save backend (FLASH1M or plain SRAM/FRAM, as on the EZ-Flash Omega) is detected at runtime

Controls

Menu

Action	Key
Change selection	D-Pad
Confirm	A
Back	B

Receive

1. On the Game Boy Camera, press the SELECT button to open the menu, move UP to LINK and press A, move DOWN to TRANSFER and press A.
2. On the Game Boy Advance, select "Receive photo", then A to start listening.
3. On the Game Boy Camera, choose SEND and pick the photo you wish to send. This will delete the photo from your Game Boy Camera.
4. The complete photo appears on the GBA's screen as soon as it arrives.

View

The view menu opens the most recent photo first. Press LEFT to view the previous photo or RIGHT to view the next photo. The X/Y counter in the bottom-left is the number of the current photo and the number of photos saved.

Press A to open the options: Send Photo at the top, Delete Photo on the left, and Receive Photo on the right. Select a menu option with the D-Pad and press A to confirm or B to close the options. In View, SELECT also deletes the current photo.

Send

The send menu works similarly to the view menu: LEFT/RIGHT choose a photo, and A opens the options. To send, choose Send Photo (the top option) and press A.

1. On the Game Boy Camera, press the SELECT button to open the menu, move UP to LINK and press A, move DOWN to TRANSFER and press A.
2. On the Game Boy Advance, select "Send photo", choose a photo with LEFT/RIGHT, then press A to open the options, select Send Photo, and press A to wait for acceptance.
3. On the Game Boy Camera, choose RECEIVE.

Building

Requires Docker (uses the official devkitpro/devkitarm image):

./build.sh          # -> PixelPoach.gba
./build.sh clean

Host-side tests:

make -C tests/host run

The portable layers (checksums, save layout, 2 bpp decode, trade round-trip) are verified without hardware by compiling them with plain gcc. Generated assets (the font) are committed.

Layout

src/        application source
  link/     GBA link-port bit-bang driver (master + slave, alternating clock)
  cam/      camera trade protocol, .sav builder, photo store
  ui/       title, menu, receive/send scenes, photo viewer
  storage/  save backend (runtime-detected FLASH1M or SRAM)
  gfx/      generated font
tests/host/ host-side unit tests
tools/      deploy, mGBA capture, and .sav extraction scripts

Legal

Copyright © 2026 Scott Ratchford. PixelPoach's original code and documentation are available under the MIT License. See LICENSE for the full text.

Not affiliated with, endorsed by, or sponsored by Nintendo. Game Boy, Game Boy Color, Game Boy Advance, Game Boy Camera and Game Boy Printer are trademarks of Nintendo.