LeBoy

Disclaimer: GAME BOY is a trademark of Nintendo Co., Ltd.

LeBoy is a GB emulator written in pure C#, with an optional MonoGame desktop front-end (but can be easily integrated in other presentation frameworks such as Unity). It is designed to be cross-platform, with a current target set to .NET 5 (currently supporting Windows, MacOS, and Linux, but should already run as-is on iOS, Android as well).

The core emulation library (LeBoyLib) is a separated pure C# project that can easily be embedded into any kind of C# project. It is meant to be agnostic of any graphical, sound, or input backend.

LeBoy is not meant for accuracy or speed. It is an educational project with a focus on straightforward, readable, and well documented code to learn more about the basics of making emulators.

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What's missing and known issues

LeBoy is not yet complete. Here's what's currently missing:

• Sound is not implemented yet;
• Real time clock (RTC) support is absent and queries to clock registers will return 0;
• GBC and SGB are not supported, only the base GB (DMG) is fully supported (which is the priority of the project);
• Memory Bank Controllers (MBCs) are partially implemented (only MBC1, MBC2, MBC3, and MC5 are supported, without RTC support).

Known issues:

• OAM priority and read/write: OAM emulation is not quite accurate, some sprites have wrong priorities and this may result in sprites not displaying, or being displayed above/under other elements.

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Building LeBoy

LeBoy requires .NET 5 and should build as-is.

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Using LeBoyLib

LeBoyLib is the main emulation library and is independent of any graphical, sound, or input backend. You can build it and use it in any kind of C# project.

Here are some code snippet to get started with LeBoyLib.

Initializing and loading a ROM:

GBZ80 emulator = new GBZ80();

// Loading a rom into a byte[]
byte[] rom = System.IO.File.ReadAllBytes("MyRomFile.gb");

// Loading the rom
emulator.Load(rom);

Executing the emulation:

// suggesting that this part runs from a thread
while(true)
{
    // DecodeAndDispatch emulates the next CPU instruction.
    // It returns the number of CPU cycles that have been used
    // and you can use GBZ80.ClockSpeed to synchronize the emulation speed
    // with the host CPU speed (this example runs uncapped emulation speed).
    emulator.DecodeAndDispatch();
}

Getting the backbuffer:

// This returns a 32bit BGRA (1 byte per component) encoded byte[] of the full 160x144 GB display.
// The first pixel is the leftmost top pixel and it continues line by line.
byte[] backbuffer = emulator.GetScreenBuffer();

Inputs:

// Inputs can be updated through the JoypadState array.
// Here's an example using a MonoGame implementation.
GamePadState gamePadState = GamePad.GetState(PlayerIndex.One);

emulator.JoypadState[0] = (gamePadState.DPad.Right == ButtonState.Pressed); // right
emulator.JoypadState[1] = (gamePadState.DPad.Left == ButtonState.Pressed); // left
emulator.JoypadState[2] = (gamePadState.DPad.Up == ButtonState.Pressed); // up
emulator.JoypadState[3] = (gamePadState.DPad.Down == ButtonState.Pressed); // down
emulator.JoypadState[4] = (gamePadState.Buttons.B == ButtonState.Pressed); // B
emulator.JoypadState[5] = (gamePadState.Buttons.A == ButtonState.Pressed); // A
emulator.JoypadState[6] = (gamePadState.Buttons.Back == ButtonState.Pressed); // select
emulator.JoypadState[7] = (gamePadState.Buttons.Start == ButtonState.Pressed); // start