stoicgb

A Game Boy emulator written in C++ to develop a better understanding of how certain machines work together in a precisely synchronized fashion in order to keep a gaming addict like myself addicted.

It's not the most accurate emulator out there, but it's accurate enough to play some of the games I grew up with, such as my beloved Pokémon Yellow.

Usage

Tested on MacOS so far.

Dependencies

cmake, SDL2, SDL2_ttf, tinyfiledialogs (included in repo)

TODO: My CMakeLists.txt is not the most sophisticated in finding SDL2. I'll work on that. For now, we have to manually set the paths to SDL2_ttf.

Building

cmake . 

Running

./stoicgb          Opens a file dialog for selecting a standard Game Boy ROM

Features

• Accurate CPU with correct opcode implementations and timings. It is the CPU, at least in my implementation, that is central to synchronizing all components.
• PPU (whose timings are accurate enough to render many games).
• Working stereo audio using SDL_QueueAudio (again, timings are accurate enough for many games).
• Memory Bank Controllers: MBC0 (no MBC), MBC1, MBC2, MBC3, MBC5 (no RTC support) .
• Battery for saving (via external RAM dumps).
• Loading of save files (automatically attempts to load from the same directory as a battery-supported ROM).
• Disassembler (for debugging).

I still have a lot of work to do in terms of accuracy, and I also plan on adding more features, but I'm happy with the progress I've made so far.

Controls

Key	Action
Enter	Start
Space	Select
↑	Up
↓	Down
←	Left
→	Right
Z	A
X	B
esc	Quit

Tests

Blargg's Test Result cpu_instrs ✅ instr_timing ✅ interrupt_time ✅ (DMG only) mem_timing ✅ mem_timing-2 ✅ dmg_sound ❌ oam_bug ❌ halt_bug ❌

Gekkio's Mooneye Test Result bits ✅ instr ✅ interrupts ✅ oam_dma ❌ ppu ❌ timer ✅ TODO: List all the tests. Many pass. Alas, much fail.

Matt Currie's dmg-acid2 ✅

Game GIFs

Pokémon Yellow	Pokémon Yellow (yes, again)
Donkey Kong Land	Super Mario Land
The Legend of Zelda: Link's Awakening	Metroid II: Return of Samus
Tetris	Dr. Mario

Resources

I'm grateful to those who have made Game Boy documentations available to the public. I've learned a lot from them, and I could not have made this emulator without them. Here is a non-exhaustive list roughly categorized by topic of some of the resources I used:

CPU

• izik1's gbops, an accurate opcode table for the Game Boy
• gekkio's Game Boy: Complete Technical Reference
• Sharp Microcomputer Databook (p. 140)

PPU

• hacktix's GBEDG: The Gameboy Emulator Development Guide
• Low Level Devel's Gameboy Emulator Development Tutorial Series

APU

• NightShade's Game Boy Sound Emulation
• gbdev's Gameboy sound hardware
• A Reddit comment by the creator of GhostBoy

Timings

• AntonioND's The Cycle-Accurate Game Boy Docs

and, of course, Pan Docs.