Memorix101 / LeBoy

Cross-platform Game Boy emulator written in C# using MonoGame

LeBoy

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

LeBoy is a GB emulator written in C# and using MonoGame as a graphical and sound output. It is designed to be cross-platform (currently supporting Windows, MacOS, and Linux, but should already run as-is on iOS, Android, and consoles). The core emulation library (LeBoyLib) is a separated pure C# project that can easily be embedded into any kind of C# project.

LeBoy is not meant for accuracy and speed, it is a pet project which initially started for educational purposes.

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What's missing & known issues

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

• Sound: it currently doesn't generate sound;
• Real time clock (RTC): clock support is absent and queries to clock registers will return 0;
• GBC & SGB: only the base GB (DMG) is fully supported;
• Some Memory Bank Controllers (MBCs): only MBC1, MBC2, MBC3, and MC5 are supported (without RTC support).

Known issues:

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

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Future plans

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

• Fixing any rendering issues;
• Implementing sound;
• Implementing missing MBCs;
• Refactoring GBMemory and optimize memory read/write to enhance performance;
• Refactoring the LCD controller emulation to be less hacky and faster;

GBC support is not a priority for now.

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Building LeBoy

LeBoy requires a bleeding edge version of MonoGame. Make sure that you are either using the latest development build installer or building MonoGame from sources (develop branch).

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Using LeBoyLib

LeBoyLib is the main emulation library and is independent of MonoGame. 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[]
using (FileStream fs = new FileStream("MyRomFile.gb", FileMode.Open))
{
    using (BinaryReader br = new BinaryReader(fs))
    {
        byte[] rom = new byte[fs.Length];
        for (int i = 0; i < fs.Length; i++)
            rom[i] = br.ReadByte();
        // loading the rom
        emulator.Load(rom);
    }
}

Executing the emulation:

// better to run this 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
    emulator.DecodeAndDispatch();
}

Getting the backbuffer:

// this returns a BGRA encoded byte[] of the full 160x144 GB display
byte[] backbuffer = emulator.GetScreenBuffer();

Inputs:

// inputs can be updated through the JoypadState array
// here's an example using MonoGame
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