3DS Homebrew Development

This page contains general information for 3DS Homebrew developers.

If you have any questions, you can come to GBAtemp's main homebrew development and help thread. It contains shared sources, examples and libraries.

You can find all known resources (hardware registers, syscalls, utilities) to develop your homebrew on 3dbrew.

To develop 3DS homebrew you need a development environment consisting of tools, scripts and libraries which will be detailed below. The languages used to write homebrew is C and C++ (and ASM). The sources are compiled to binary using GNU GCC-ARM or devkitPro with DevkitARM. Python can also be used to compile ARM9 homebrew (Launcher.dat format). The available tools and SDK work on Windows 32/64bit and Linux.

Install devkitPro

DevkitPro is an essential set of toolchains for homebrew development.

• Linux/Mac OSX: Follow this guide.
• Windows: Use the automated-installer. Install in C:\devkitPro\ and it will install all the latest versions of the required programs (you can disable devkitPSP, but be sure to enable CTRULib in DevkitARM menu). It will create the environment variables automatically.

You may also want to install other libraries/tools if your project requires them.

Compiling sources

If you simply want to compile a homebrew project without (or after) editing it, you can use the make utility from the command prompt/terminal.

1) Windows: Open a Command Prompt (Run -> cmd); Linux/Mac OSX: Open a Terminal from your applications

2) Navigate to the project directory (change to the correct path)

cd c:\path\to\your\project

3) Run make

make

Common errors

cannot find 3dsx_crt0.o: No such file or directory

In your makefile, find -mfloat-abi=softfp and change it to -mfloat-abi=hard. You shouldn't ever use softfp for 3DS homebrew.

(name) uses VFP register arguments but (name2) does not

Part of your project or the libraries you use were compiled with -mfloat-abi=softfp while other parts were compiled with -mfloat-abi=hard. Make sure to use -mfloat-abi=hard everywhere. You may have to manually recompile the libraries you use, if needed.

SMDH

Every homebrew application has an smdh file, containing additional information:

• Icon
• Name of the application (Short description)
• Description of the application (Long description)
• Name of the author (Publisher)

This information is used in The Homebrew Launcher (3DSX), and in the home menu (3DS/CIA).

The icon is a simple 48x48px png file. You can place this png in your project folder (the same folder as your Makefile is in) and name it icon.png. If no icon.png is present, a default icon from the ctrulib folder will be used.

The other data can be set in the Makefile directly:

APP_TITLE        := My Application 
APP_DESCRIPTION  := A description of my app
APP_AUTHOR       := Me

The SMDH file is automatically created when building the project (unless you explicitly set NO_SMDH in the Makefile).

You can also manually build the SMDH using bannertool by steveice10:

bannertool makesmdh -s "My application" -l "A description of my app" -p "Me" -i icon.png -o myapplication.smdh

Editor setup

This section explains how to set up various editors to edit and compile (existing) homebrew projects. If you want to start a new homebrew project, you should preferably copy an example project and edit the sources.

Programmers Notepad

The Programmers Notepad is (optionally) installed by the devkitPro installer.

1) File -> New -> Project
Give it a name and save anywhere.

2) Right click the project -> Add Files
Now navigate to the example you want and add the files from that folder (eg. Makefile, readme.md, ...)

3) Right click the project -> Add Magic Folder
Navigate to the example directory again and add the source folder within. Repeat this for any other folders in the example (if any).

4) You can build the project using Tools -> Make
Make sure the project you want to build is the active project (Right click project -> active project)

Visual Studio 2015 (community)

When installing Visual Studio, make sure to install the Visual C++ packages!

1) File -> New -> Project From Existing Code...

2) In the dropdown, choose Visual C++ and click Next

3) Under Project file location, navigate to the folder with all sources. Enter a name for the project and click next.

4) Use external build system, Next

5) Build command line:

make

Clean command line:

make clean

Leave the rest blank. Click Finish.

6) Right click project (in the solution explorer) -> properties

7) Under VC++ directories -> General -> Include directories, add the devkitARM and ctrulib include directories (change if needed):

C:\devkitPro\devkitARM\include
C:\devkitPro\libctru\include

Make sure not to remove anything already in the box! You can add any other include folder that the project may need as well. In the end it'll read something like:

C:\devkitPro\devkitARM\include;C:\devkitPro\libctru\include;$(IncludePath)

Click OK

8) (Optional) Right click project -> Add -> Existing Item
Choose the Makefile and any other files you want to add, then click Add. This step isn't required, but allows you to edit the Makefile etc. from the editor.

Alternatively, you can use "Show All Files" under the "Project" menu (on the top) to display all files and folders as they are on the file system.

9) You can now build the project (Right click -> Build)

Eclipse CDT

Tested with the standalone Eclipse Mars CDT on Linux. Instructions may be slightly different for other cases.

1) File -> New -> Makefile Project with Existing Code

2) Under Existing Code Location, navigate to the folder containing the code.
You can leave both C and C++ checked, even if the project only contains one.
Under Toolchain for Indexer Settings, choose a valid Toolchain (eg. Linux GCC)

3) Right click the Project in the project explorer and choose properties.

4) Go to C/C++ Build -> Environment.
Here you need to add the DEVKITPRO and DEVKITARM variables, with their correct paths, eg.

Name	Value
DEVKITPRO	/opt/devkitpro
DEVKITARM	/opt/devkitpro/devkitARM

Make sure to change the values to the paths on your system.

5) This step isn't needed to build, but it will make Eclipse recognize the external libraries when editing code. Go to C/C++ General -> Paths & Symbols -> Includes
Under "GNU C" (or "GNU C++", or both, depending on what files your project has), add the following include directories:

/opt/devkitpro/devkitARM/include
/opt/devkitpro/libctru/include

Again, change the paths if needed. When finished, click OK.

6) You can now build the project. Right click project -> Build project

3dsx homebrew

Homebrew in this format is the most common, and can be played with ninjhax/ironhax/tubehax. No additional steps have to be taken to create this kind of homebrew; it is the default format produced when using make.

You can find ctrulib homebrew examples here: https://github.com/smealum/ctrulib/tree/master/examples

Launcher.dat and .3ds homebrew

If you don't need Kernel access, prefer developing homebrew in 3dsx format. Remember that the .dat format works only on 4.1.x-4.5.x consoles.

Convert .elf to .3ds

To create a .3ds file (or .cia), you need some additional files in your project (TODO: Make guide on how to create these):

• An RSF file - Contains various info such as permissions etc.
• An icon.bin - The icon and information for the home menu. This is equivalent to the compiled SMDH file, so you can just use that one.
• A banner.bin - The banner for the top screen

You should preferably put them in a subfolder (for example "cci") in your project folder.

After building the project (see above), you should have an .elf file. You can convert this into a .3ds file:

• Download makerom (and compile it with make if needed)
• Add the folder where you placed the makerom executable to your PATH environment variable
• Open a command prompt/terminal and navigate to your project

cd c:/path/to/your/project

• Run the following commands:

arm-none-eabi-strip [ELF file]
makerom -f cci -o [Destination .3ds file] -rsf [RSF file] -target d -exefslogo -elf [ELF file] -icon [icon file] -banner [banner file]

For example:

arm-none-eabi-strip myproject.elf
makerom -f cci -o myproject.3ds -rsf cci/gw_workaround.rsf -target d -exefslogo -elf myproject.elf -icon cci/icon.bin -banner cci/banner.bin

TODO: How to Build a CIA guide

Releasing

When you are ready to release your homebrew application, create a new thread in the Homebrew Development section. In this thread, you can describe your project.

Make sure to attach (or link to an uploaded version of) the relevant files for your homebrew. This will usually be the 3DSX and SMDH files that have been compiled. You can also include the ELF file, which will allow people to repack it with makerom to a 3DS (and CIA) file. The ELF file can also be used on 3DS Emulators (currently two available: Citra and 3DMoo).

If your project is open source, you can upload the code to GitHub. Alternatively, you can simply provide the source as a separate download, or include it with the compiled files.

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Development environment If you already installed Devkit ARM with CTRuLib, you don't need to follow the installations steps, unless you want to compile using Python instead of Makefile. Install Python 2.7.x Note: You can skip this step if you want. Go to step 2. directly if you don't want to use Python to compile your homebrew. Download the latest version of Python 2.7.x Install Python on your computer. If you are on Linux, add Python to your environment variable $PATH If you are on Windows, install it in C:\Python27\, and it should edit the environment variable "Path" automatically. If you need to do it manually, follow these steps: Go to My Computer > Right-click > Properties > Advanced tab > Environment variables > System variables In the list search for "Path", select it and press Edit/Modify At the end of the line, add this: ;C:\Python27 It will allow you to call the Python program from any place by typing "Python" in a command line window. Install a compiler You can install and use GNU Tools for ARM Embedded Processors as alternate compiler, but it will not be enough to develop ARM11 homebrew as you will need additional libraries provided by DevkitPro. If you use this compiler for ARM9 homebrew, you will also need to add the ARM binaries path to your environment variables. Follow the previous Python steps to add this path: ;C:\Program Files\GNU Tools ARM Embedded\4.8 2013q4\bin Attention, change the version in the path, do not keep 4.8 2013q but use the one you installed instead. Build script To compile your homebrew sources to an executable binary file you can use either a Python script or a Makefile script. Makefile is easier, but this guide will also detail how the Python package is created to cover and understand all installation steps. There are two packages ready to download: One for Python and one for Makefile, both made by Snailface. Just download the one you want and extract it in any folder. This will become your homebrew working folder. Create one copy per homebrew you are developing. This is how the Python package has been created: Download the files from Kane49's github, and extract to a folder of your choice. Download the files from Naehrwert's gitHub, and extract the files and the folder into the p3ds folder from the previous download. For Linux users, download the modified build.py file from Tomiga to replace the one you downloaded from Kane49's repository. Open build.by and replace both instances of: "-mcpu=mpcore -march=armv6k" to "-mcpu=arm946e-s -march=armv5te". Comment the lines: #run("copy Launcher.dat E:\\Launcher.dat > NUL") #upload("Launcher.dat") #run("del payload.bin") Compiling .dat format ARM9 If you are using Python to compile your homebrew: In your development folder, open a command line and type "Python build.py" You can also run Build.bat If you are using makefile: In your development folder, open a command line and type "make" You can also run Build.bat Your homebrew will be compiled as a Payload.bin and will be encapsulated into a Launcher.dat file ready to launch using a ROP exploit. You can provide both the .bin and .dat file when you share your homebrew. ARM11 Open a command line window and navigate to your homebrew folder and type "make". It will create a <folder name of your project>.elf file. To convert the elf file to .3ds format: Download MakeROM by 3DSGuy. Alternative Download Link Extract it to a new folder. If you don't want to make homebrew for Gateway 3DS flashcart, you can find file requirement and command line format to use with MakeROM on 3dbrew.org. converting .elf to .3ds format If you want to make the .3ds file working on Gateway 3DS flashcart homebrew menu, download the Gateway Card Homebrew Files, by 3DSGuy, and extract its content into the Makerom folder. Open a command line window and navigate to the MakeROM folder. type build <elf file> <output 3ds file> where <elf.file> is the name of your homebrew.elf, and <output 3ds file> is the name of the .3ds file example build myproject.elf AwesomeGame.3ds Making your own Homebrew Icon and Banner If you want to create your own banner and icon for ARM11 homebrew, you can use 3DS Banner Maker, by Snailface, to convert png pictures to the correct format used by MakeROM. It requires Python 2 and PIL (Python Image Library).