Game Boy Emulator

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A simple Game Boy Emulator written in C++ with a scanline renderer and MBC support.

The core emulator (lib) can be extracted and used with custom implementations (e.g. on embedded systems). A desktop implementation (test) with SDL2 and Dear ImGUI is the main way to use this emulator.

This emulator was primarily written for educational purposes, so don't expect anything extraordinary (˙ ͜ʟ˙)

Authors

• @omrawaley

Demo

(The actual emulator is less choppy)

Features

• Core emulator library
• CLI ROM loading
• Scanline rendering
• Customizable palette
• Expandable MBC support (only MBC1 currently)
• GUI

API Reference

void reboot() Reboot the emulator.

std::array<u8, 160 * 144 * 3>& getFramebuffer(); Get the RGB24 framebuffer.

std::string getTitle(); Get the ROM title.

void pressButton(Joypad::Button button); Press a button.

void releaseButton(Joypad::Button button); Release a button.

void loadBootROM(std::string path); Load a Boot ROM/BIOS.

void loadROM(std::string path); Load a ROM.

void step(); Render 1 frame.

Installation

Use the bundled CMakeLists.txt to generate a Makefile and compile with make.

cmake CMakeLists.txt
make

When running cmake, you have the option to pass -DERROR=ON which enables printing errors to the console.

Usage

./bin/gb <path-to-boot-rom> <path-to-rom>

Keys

M Show the menu bar.

Tab Hold to speed up the emulator.

Esc Quit the program.

To-Do

• Add more CLI options
• Add a debugger to view internal state and the bus
• Add the ability to take screenshots
• Add more robust palette handling
• Rewrite the PPU to improve time complexity
• Add MBC3, MBC2, and MBC5 support
• Add the ability to view the serial port via the GUI
• Add a proper error collector/reporter
• Format code to expose public functions first
• Remove the IO array in bus.h and handle unimplemented IO registers properly

Contributing

Contributions are always welcome! I'd love to learn how I can improve this emulator.

License

Apache 2.0

Dependancies

Dear ImGui - MIT

(Not bundled) SDL - zlib