The GBA homebrew scene has been growing steadily over the years, with one of the most recent homebrew projects for the system allowing for such technological wonders such as running Tomb Raider on the 32-bit handheld with the help of the open source engine OpenLara.

All of this is thanks to the effort put together by the GBA homebrew devs, being lead by the GameBoy Development community over at gbdev.io, where they share a vast variety of libraries and documentation about the GameBoy family of handhelds, put together over the decades to allow for homebrew developers and romhackers alike to create new and fascinating projects for the beloved Nintendo handheld.

One such collection of libraries is the GBA Link Connection, which allows for the developer to interact with the serial port found in the Game Boy family of systems, which was frequently used to allow some sort of multi-player functionality with the handheld when connected to other Game Boys. The goal of GBA Link Connection is to allow homebrew games to make full use of the serial port, and allow multi-player functionality within homebrew developed games.

During the weekend, the GBDev team showcased a breakthrough for these libraries, that one being the Link Cable Multiboot library and Link Wireless Multiboot library, which allow for a Game Boy Advance game with either the Link Cable or the Wireless Adapter connected to send over small 256KiB programs to other GBA systems.

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This opens up a lot of possibilities for homebrew development for the Game Boy, Game Boy Color and Game Boy Advance systems, as this could possibly be compared to some degree to what the DS did for some multiplayer games when it came to connections with other DS systems that didn't have the same cart inserted.

Those interested can check out the GBA Link Connection set of libraries over at their open source GitHub repository.

GBA Link Connection Library at GitHub

 

[patters]

could someone explain the implication of this? Never had a GBA myself....

A multiboot program is one that entirely fits within and is executed from the 256KB of external work RAM of the GBA. The GBA has a further 32KB of internal work RAM which this code can use while running. This means the GBA can run it with no cart inserted. If you boot a GBA with Start+Select held, it will make a little extra sound and wait for a multiboot loader via serial port handshake. It will wait for this by default while the boot logo is displayed if no cart is inserted.

This ability is used by those commercial games which allow you to play multiplayer using a single game cart (typically a cut down version of the full every-player-owns-a-copy-of-the-game experience). So Mario Kart for instance is able to send a single race course and the game engine to other GBA systems using the serial link cable, for a match.

GameCube games also made use of this and could send programs to the GBA using a cable connected to a controller port: e.g. in Animal Crossing you could earn emulated NES games that could be sent to a GBA in this manner. Also your player character could travel to an island and 'live' there for a while, on the GBA via a mini game. It was cool stuff, and very innovative.

Another great example is Bomberman Tournament which allows full featured multiplayer fun using a single game cart for four GBA consoles.

Some of the multiboot minigames are perfectly serviceable in their own right. For example Panel de Pon, or NiGHTS Score Attack. They can be converted to .gba ROMs using a tool and booted direct from a flashcard. The utility which is the subject of this forum thread could be used to send the .mb multiboot files to other Gameboys over the link cable.