FenrirWolf / gbatest

A quick explanation of how to setup rust to build GBA games

First Time Setup

ketsuban is the wizard who explained to me how to do this stuff.

1. Install devkitpro. They have a graphical installer for Windows, or you can use pacman or whatever for linux things I guess. The goal here, among other things, is to have a binutils setup that's targeting arm-none-eabi. We'll also use some of their tools that are specific to GBA development so if you for some reason already have the appropriate binutils then you probably still want devkitpro.

   • On Windows you'll want something like C:\devkitpro\devkitARM\bin and C:\devkitpro\tools\bin to be added to your PATH. I'm not sure on the directories for other systems. If you know then file a PR with the info.

2. Next we use cargo install cargo-xbuild to get that all setup.

3. Create a binary project. We're going to want nightly rust for this, so if you don't already have it set to default to nightly you should set that up for this project.

4. Clone this repo. It has an appropriate main.rs that will draw three test dots as well as other support files:

• crt0.s
• linker.ld
• thumbv4-none-eabi.json

5. Be aware that you must run arm-none-eabi-as crt0.s -o crt0.o any time the crt0.s file changes. The provided crt0.o file in this repo is correct, but if you make any changes to crt0.s you'll need to rebuild crt0.o.

6. Build with cargo xbuild --target thumbv4-none-eabi.json

• The file extension is significant, and cargo xbuild takes it as a flag to compile dependencies with the same sysroot, so you can include crates normally. Well, no_std crates that can run inside a GBA at least.
• This generates an ELF binary that some emulators can run directly (which is helpful because it has debug symbols).

7. Also you can patch up the output to be a "real" ROM file:

• arm-none-eabi-objcopy -O binary target/thumbv4-none-eabi/debug/gbatest output.gba
• gbafix output.gba

8. Time to read the Tonc tutorial and convert all the C code you see into rust code.