Mega Drive SDKs

Mega Drive
SEGA
SDK
Learn how to configure your development environment
Author

ProtossGP32

Published

May 7, 2023

Introduction

TODO: talk about SDK for Mega Drive

Getting started

Installing SGDK

We’ll be deploying the excellent and mature SGDK by Stephane Dallongeville, that allows to develop Mega Drive games in C language.

Developing on Linux

SGDK works natively on Windows, but there are options to make it work on Linux:

  • Using Wine
  • Using Marsdev. Here we install the SDK locally instead of using a Docker image for building the project
    • Quick installation steps: link
    • Compile time is long, so let it do its thing
    • Set the $MARSDEV environment variable in .bashrc like this: export MARSDEV=/home/$USER/mars
    • Create a softlink within the $MARSDEV path that points to the SGDK created on compile time within the Marsdev repository. This is required for later use in VS Code extensions
    Include SGDK to Marsdev path
    cd $MARSDEV
ln -s /path/to/git/repository/marsdev/sgdk sgdk

Compiling

We can use the following alternatives to compile our projects:

  • Locally, previously compiling SGDK or Marsdev toolchains
  • Using a Docker image (Dockerfile provided in Stephane’s repository). Just follow these instructions to build your own SGDK docker image and use it to compile your code
    • This approach also uses Wine within the Docker container to launch SGDK
  • Using Doragasu, another Docker image. Again, just use these instructions to build your project
    • This approach uses native Linux compiler, much faster

Some compile times comparison:

Approach Time
SGDK docker 13.721s
Doragasu docker 6.952s

Debugging

When using Marsdev, the GDC for m64k (m68k-elf-gdb) isn’t compiled by default. Launch the following command from the git repository root path:

Compiling m68k GDB
# Install required dependencies
sudo apt-get install libgmp-dev

make m68k-gdb

Take note of the binary path as we’ll have to check it when configuring our text editor.

We also need an emulator to run the code and to properly attach when debugging. BlastEm is a relatively modern emulator with embedded debugger. Gens is another good option with very intuitive GUI for debugging purposes.

BlastEm - Use nighly builds

  • Download the latest nightly build. At the moment of writing this article (2023/05/07), the available stable 0.6.2 version fails due to missing instructions
  • Uncompress the file and add the resulting directory to your $PATH environment variable
    • Make sure to update it in your .bashrc file

Text editors

VS Code

We’ll be using Genesis Code extension by Zerasul to help us with the programming side of things. This extension is compatible with all previously mentioned compiling options, both Docker images and Marsdev.

Configuration:

  • Check Doragasu Image if you plan on using Doragasu GitLab image for building purposes
  • Set docker as the Toolchain Type if you plan on using Docker images on build stage
  • Set the $MARSDEV env variable

Creating a new Mega Drive project is as simple as launching Genesis Code: create project from the Command palette. Then check that the .vscode path has been created and make sure that both launch.json and settings.json point towards the right MARSDEV paths, else VS Code won’t include the SGDK headers to the project.

Debug configuration

In order to properly debug using BlastEm, check the .vscode/launch.json file and make sure that everything points towards the correct paths:

  • program: should be the ELF program created when compiling with the debug options enabled (Genesis Code: Compile for Debugging in the command palette).
    • This file must include the symbols
    • When compiling with SGDK, the generated file is out/rom.out
  • sourcefileMap: it must point to the SGDK src path, retrieved using the Marsdev make targets
  • miDebuggerPath: don’t touch it. Just make sure you compiled the m68k-elf-gdb as told in previous steps
  • miDebuggerArgs: make sure that the emulator name is correct and that it launches the out/rom.bin file

Once done, go to the Run and Debug option (CTRL + SHIFT + D), select the Debug with gdb remote profile and click on play. If a breakpoint has been set in your code, the Debug var should start to show some info:

VS Code debugging a Hello World example
TODO: create a VS Codium Docker image that already includes Marsdev installed