Modest GB

Modest GB is a Game Boy Emulator (DMG only) written in C++.

Building

In theory, the emulator should be cross platform, but it has only been tested on Windows.

1. Install CMake 3.21 or greater - https://cmake.org/download/

2. Clone the repo and its dependencies:

   git clone --recurse-submodules https://github.com/ShannonHG/Modest-GB ./Modest-GB
   

3. Build using CMake:

   cd ./Modest-GB
   mkdir build
   cd build
   cmake ..
   cmake --build . --config Release
   

4. The build can be found in /Modest-GB/build/Release/

Controller/Keyboard Mapping

The button mapping can be modified in File -> Settings -> Controller/Keyboard, but the default configuration is listed below.

Game Boy	Controller	Keyboard
A	A	J
B	B	K
Start	Start	P
Select	Select	O
Right	D-pad Right	D
Left	D-pad Left	A
Up	D-pad Up	W
Down	D-pad Down	S

Cartridges

Listed below are all of the cartridge types that are currently supported. Attempting to load a ROM that uses an unimplemented memory bank controller, will cause the emulator to default to using MBC1.

• ROM only
• MBC1
• MBC3
• MBC5

Audio

When the emulator is opened, it will attempt to select the audio output device saved in the Modest-GB.config file. However, if the configuration file does not exist yet, or the selected output device is not currently connected, then the first available output device will be used instead. The output device can be changed at any time by navigating to File -> Settings -> Audio, and changing the Output Device setting.

Saved Data

By default, saved data is stored in /Modest-GB/Saved-Data/. However, the emulator can also be configured to store saved data in the same folder as the ROM file. This can be done by navigating to File -> Settings -> Saved Data, and changing Saved Data Location to ROM Directory.

Dependencies

• SDL - https://www.libsdl.org/
• yaml-cpp - https://github.com/jbeder/yaml-cpp/
• Dear ImGui - https://github.com/ocornut/imgui
• Native File Dialog Extended - https://github.com/btzy/nativefiledialog-extended

References

• Pan Docs - https://gbdev.io/pandocs/
• gbops - https://izik1.github.io/gbops/index.html
• Additional opcode table - https://meganesulli.com/generate-gb-opcodes/
• Game Boy: Complete Technical Reference - https://github.com/Gekkio/gb-ctr
• Game Boy Sound Hardware Documentation - https://gbdev.gg8.se/wiki/articles/Gameboy_sound_hardware
• The Ultimate Game Boy Talk - https://www.youtube.com/watch?v=HyzD8pNlpwI