"GBA Link Connection" homebrew libraries now allows sending multiboot ROMs via the GBA's Link Cable or Wireless Adapter

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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.



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.

:arrow: GBA Link Connection Library at GitHub
 

Nephiel

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I vaguely recall a homebrew NES emu for GBA that made use of this multiboot feature to send a copy of itself, plus the ROM you were playing, to a second GBA, over link cable, and play 2-player games on both. Only worked with small ROMs because of limited RAM size, but still, it was an amazing feat.
 

Disorarara

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I vaguely recall a homebrew NES emu for GBA that made use of this multiboot feature to send a copy of itself, plus the ROM you were playing, to a second GBA, over link cable, and play 2-player games on both. Only worked with small ROMs because of limited RAM size, but still, it was an amazing feat.
This was actually also possible on the official NES GBA games
 
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N7Kopper

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Just the other day I was wondering if there was a GBA homebrew that let you send multiboots (fun fact - the official name is joyboot - or joycarry in Japanese) and now we have libraries for linkups. I find it funny how we understood Gamecube linking first.
 

patters

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The thing is, cool as this is as a tech demo, if you have multiboot programs on your flashcart, there is no need for this since you can safely pull out the cart when they're loaded.

So imagine you want to load a multiboot game or emulator+ROM on a friend's GBA - you can just hand them your cart instead. They load it, then pull it out with the system still powered on, and hand back the cart.

Flubba's emulators had a 'Go Multiboot' option for this purpose if the ROM was less than 192KB (so emu+ROM could fit with the 256KB of EWRAM).
 
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EvilJagaGenius

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I think it'd be really cool to see the homebrew PrBoom port with link cable multiplayer. I've thought about trying it myself, I just haven't had time (that and I'm not quite sure where to start).

I wonder how much Doom you can fit into 256KB.
 
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