Introducing BootFriend: unofficial custom firmware for WonderSwan Color

Published on February 16, 2023

For a while now, I’ve been involved in the WonderSwan homebrew scene - for those unfamiliar, it’s a handheld consoles which was moderately successful in Japan but failed to launch outside of it. I got to make a demo or two, I got to contribute towards emulator accuracy, I got to write a homebrew toolchain which… honestly is stuck in development hell due to perfe- It was and continues to be a fun little excursion.

Today, I’d like to show another project I’ve made - custom firmware for the WonderSwan Color/SwanCrystal consoles! (Well, sort of - it’s actually a custom splash screen that happens to take over execution when some conditions are met.) It unlocks a few neat features as a result of being able to run at console boot time:

  • “multiboot” (loading software to RAM via serial port),
  • backing up the IPL (boot ROM),
  • managing game data & saves,
  • flashing cartridges without an external flasher,
  • the ability to create a (simple) custom splash screen with a web interface,
  • fast boot (by reducing the splash duration, I guess?).

I’m aware it’s a somewhat obscure platform; however, I believe it will be of use to a niche of enthusiasts, and I hope it delights those among you who enjoy such things :-)

Installation instructions, downloads and more information are available here: