yordrar / gb_emulator

A small, feature-complete GB emulator written from scratch in C++

GB Emulator

This is a small GameBoy emulator I made as a side project to get into the world of emulation.

Although it doesn't implement some quirks or bugs found in real hardware, it is a complete emulator capable of running some of the most complex ROMs. I decided not to make it more accurate to keep the scope small, as I intended this to be a quick side project.

It features keyboard and Xbox controller support through Xinput, and memory bank controllers 1, 2, 3 and 5, including RTC clock emulation and battery-backed RAM. The emulator periodically saves the battery-backed RAM banks to a .sav file whenever the ROM writes to them.

Usage

To open a ROM file, either drag it to the built exe file or pass the path as the first parameter in the command line, like

> gb_emulator.exe MyRom.gb

You can use either the keyboard or an xbox controller as input. Keyboard controls:

• Arrow keys: D-Pad
• Z: A button
• X: B button
• C: Start button
• V: Select button

The xbox controller maps the obvious buttons to the GB ones (D-Pad/Left Joystick -> D-Pad, A button -> A button, etc.)

Build

To build it, run premake in the root directory to generate files for your preferred build system. I personally use Visual Studio, for which I run 'premake.exe vs2022'. The generated build files will be inside the 'build/' folder, and the compiled binaries in 'build/bin'

Shader effects

You might notice that the shader the emulator uses is a text HLSL file inside the 'shader/' folder. This is a deliberate choice. This shader gets built at runtime by the emulator, so you can edit it to create your own post-processing or fullscreen effects without recompiling.