GBScribe Emulated

GBScribe Emulated

Interactive browser demo of GBScribe, the Game Boy Advance word processor and pixel-art tool, connected to an emulated Game Boy Printer

Software Web

Overview

GBScribe Emulated is a browser demo of GBScribe, my word processor and pixel-art drawing tool for the Game Boy Advance, connected to an emulated Game Boy Printer. It runs the unmodified GBScribe ROM in a WebAssembly build of mGBA, so you can type, draw, print, tear off the paper, and export the result without owning any of the hardware.

Try Now View on GitHub

How It Works

GBScribe bit-bangs the original Game Boy Printer protocol over the GBA link port in general-purpose GPIO mode. Most browser GBA emulators do not implement that mode, and none of them support the Game Boy Printer.

  • mGBA in WebAssembly runs the unmodified GBScribe ROM.
  • GPIO link-port channel clocks the printer from RCNT GPIO mode and passes its replies back to the emulator core.
  • Serial-level Game Boy Printer parses the real 0x88 0x33 packet protocol, buffers the 2bpp tile data, runs the motor, and physically advances paper.
  • Interactive shell wraps the emulator in a clickable GBA, plugs a Link Cable into the printer, and lets you tear the output off and export it.

The printer you see in this demo is not just a mock-up of the printer output. The outputs use the exact data that GBScribe sends to a real Game Boy Printer. The emulator detects the printer with its normal INQUIRY probe, streams its normal DATA chunks, and polls the normal PRINTING status bit. Powering the printer off will stop GBScribe from sending it any data.

Features

  • Complete GBScribe ROM with word processor and drawing tools
  • Clickable and touch-friendly GBA controls, plus remappable keyboard bindings
  • Guided first-run tour
  • Emulated Game Boy Printer with power, feed, paper rolls, jams, and tearing
  • PNG, BMP, and PDF export, plus printing through the browser
  • Saves, control bindings, and printed pages kept locally (with permission)
  • No data sent to a server at runtime
  • Uses real photos of my custom Game Boy Advance and Game Boy Printer

Technical Stack

  • Emulator: mGBA compiled to WebAssembly, with a custom GPIO link-port channel
  • Front end: JavaScript custom element with a Shadow DOM, Web Audio, and Web Workers
  • Printer: Serial protocol, 2bpp tile decoder, 281-dot thermal paper model
  • Export: Canvas and PDF generation in the browser
  • Hosting: Static files served by Jekyll on GitHub Pages

Acknowledgements and References

GBScribe Emulated is copyright © 2026 Scott Ratchford. GBScribe Emulated’s original code and documentation are available under the MIT License. See LICENSE.md.

The demo includes the unmodified GBScribe ROM and the AdvancePrint printer layer, both released under the MIT License. It also incorporates third-party components, including the mGBA WebAssembly core (MPL-2.0), SDL 2 (zlib), the GBA.js link-port module (BSD-2-Clause), and the Press Start 2P font (SIL OFL 1.1). See LICENSES for the full list and license texts.

Not affiliated with, endorsed by, or sponsored by Nintendo. The use of brand names and trademarks in this document is for informational purposes only.

I relied on the following documentation and open-source projects while building this demo:

  1. GBScribe for Game Boy Advance by me
  2. GBScribe by me
  3. AdvancePrint by me
  4. Game Boy Printer — Pan Docs
  5. In Depth: The Game Boy Printer by Shonumi
  6. GBATEK by Martin Korth
  7. gba-link-connection by afska
  8. mGBA by Jeffrey Pfau and contributors
  9. GBA.js by endrift (used during prototyping)