It is highly recommended to read the report to get a light introduction to Game Boy emulation. The report is relevant, eventhough you want to contribute to another emulator, or create your own.
This project is covering an emulation of the Nintendo Game Boy (DMG-01) from 1989. The Game Boy has been emulated many times before, but this project will emulate it in the programming language Python 2.7. The implementation is not based on any existing emulator, but is made from scratch. The emulation has proven to be fast enough, to run software from cartridge dumps, with the same speed as the Game Boy. Most essential components of the Game Boy, are part of the emulation, but sound and serial port are not included in this project. The implementation runs in almost pure Python, but with dependencies for drawing graphics and getting user interactions through SDL2 and NumPy.
CPython is no where fast enough to run the emulator (see PyBoy.pdf about performance). It is therefore required to use PyPy.
The code has a few dependencies, but it should be fairly easy to get it up and running. The code is developed on macOS and Ubuntu 18.04.
Ubuntu has some problems installing PyPy in parallel with the system version of CPython. Therefore, we will install the PyPy version of NumPy and PySDL2 in a virtualenv.
sudo apt update
sudo apt install git pypy pypy-dev virtualenv libsdl2-dev
cd Source
./setup.sh
Then run pypy main.py from the Source directory and choose a ROM to start.
For more advanced use, you can use pypy main.py [GameWindow] [ROM path]. For example: pypy main.py SDL2 ROMs/game.rom. Currently, the GameWindows SDL2 and dummy are supported. Use SDL2 if you want to see the screen, and dummy if you want to run PyBoy headless.
The Game Boy controls are as follows:
| Keyboard key | GameBoy equivalant |
|---|---|
| Up | Up |
| Down | Down |
| Left | Left |
| Right | Right |
| A | A |
| S | B |
| Return | Start |
| Backspace | Select |
The other controls for the emulator:
| Keyboard key | Emulator function |
|---|---|
| Escape | Quit |
| D | Debug |
| Space | Unlimited FPS |
| Z | Save state |
| X | Load state |
| I | Toggle screen recording |
Note, that debug and save/load state might not be perfectly stable.
PyBoy is loadable as an object in Python. This means, it can be initialized from another script, and be controlled and probed by the script. Take a look at tetris_bot.py for a crude "bot", which interacts with the game.
Currently, 8 methods are exposed, which should allow for complete control of the Game Boy. Please open an issue here on GitHub, if other methods are needed.
The Methods are:
- tick() Progresses the Game Boy ahead by one frame. Open an issue if you need finer control.
- getScreenBuffer() Returns a copy to the NumPy matrix of the current image displayed on the screen. The format is 32-bit ARGB.
- getMemoryValue(address) Returns the 8-bit value found at the address on the Game Boy.
- setMemoryValue(address, value) Sets the 8-bit value at the address on the Game Boy.
- sendInput(event_list) Sends a list of
WindowEvents to the Game Boy. - getMotherBoard() Returns a reference to the motherboard instance. This should be a last resort to get access to everything. If you use this heavily, then open an issue, so it can be better supported.
- getSprite(index) Returns a sprite object, which makes the OAM data more presentable. See the available methods in
Source/PyBoy/BotSupport/Sprite.py. - getTileView(high) Returns a TileView object. If given the parameter
Trueit will return a TileView for the 0x9C00-0x9FFF range, if the parameter isFalseit will provide a TileView for the 0x9800-0x9BFF range. The TileView has one method: get_tile(x, y), which returns the index of the tile. - getScreenPosition() Returns a tuple of (SCX, SCY). These coordinates define the offset in the TileView from where the top-left corner of the screen is place. Note that the TileView defines 256x256 pixels, but the screen can only show 160x144 pixels. When the offset is closer to the edge than 160x144 pixels, the screen will wrap around and render from the opposite site of the TileView (see 7.4 Viewport in the report).
I can recommend to use the TileView instead of the screenbuffer, as they contain the index of the tiles on the screen. It is much simpler to look at the 8-bit value instead of recognizing the equivalent 8x8 pixels on the screen. Same goes for the sprite memory between 0xFE00 and 0xFEA0.
To see more details about this the display and the Game boy, have a look at the "Display" part of the report, or refer to the Pan Docs, which has clear-cut details about every conceivable topic.
See results on Blargg's test ROMs. The list isn't complete, as the features in the missing tests, hasn't been implemented.
Any contribution is appreciated. The currently known errors are registered in the Issues tab. Feel free to take a swing at any one of them.
For the more major features, there are four that you can give a try:
- Sound
- Color
- Link Cable
- Unit tests and/or test ROM
If you want to implement something which is not on the list, feel free to do so anyway. If you want to merge it into our repo, then just send a pull request and we will have a look at it.
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