jamchamb / ac-mod-template

Template for Animal Crossing ACE injected mods

Animal Crossing Mod Patch Template

This is a template for Animal Crossing mod patches written in C. Some example mods can be found in the ac-mods repo.

This requires the devkitPro tools to build. See https://devkitpro.org/wiki/Getting_Started for how to install devkitpro and gamecube-dev.

Building

With gamecube-dev installed, just run make. The output will include a .patch file that holds the generated code to patch in.

Generating the GameCube save file

ac-nesrom-gen can automatically create a GCI file for the mod patches by reading the gci_build.yaml config file. If installed, the GCI file will be generated when running make.

Alternatively, use this command:

$ ac-nesrom-gen --autoheader 80002000 "Mod Name" input.patch output.gci

Import the GCI save file to a memory card and use the generic NES Console item to load the mod.

Development

Specifying patch location

Set the start address for the patch in linker.ld just before the .text section.

Note that *(.text.__entry); must always be the first entry in the .text section of the linker script.

Calling Animal Crossing functions

Here are a couple of ways to call a function that already exists in Animal Crossing:

Use function pointers

Define the function like this, using its address as the pointer value:

void (*OSReport)(char*, ...) = (void*) 0x8005A750;

Use the linker script

This uses fewer instructions, resulting in a smaller patch size.

1. Define the function like this:

   extern void OSReport(char*, ...);
   

2. Define its location in linker.ld:

   SECTIONS
   {
           . = 0x80002000;
           .text . : {
               ...
           }
           ...
           OSReport = 0x8005A750;
   }