Coffee GB is a Gameboy Color emulator written in Java 8. It's meant to be a development exercise. More info can be found in the blog post Why did I spend 1.5 months creating a Gameboy emulator?
The emulator can be build with Maven:
mvn clean package
The jar file will be available in the ./target directory.
Usage:
java -jar coffee-gb.jar [OPTIONS] ROM_FILE
Available options:
-d --force-dmg Emulate classic GB (DMG) for universal ROMs
-c --force-cgb Emulate color GB (CGB) for all ROMs
-b --use-bootstrap Start with the GB bootstrap
-db --disable-battery-saves Disable battery saves
--debug Enable debug console
--headless Start in the headless mode
Play with ←, ↑, ↓, →, Z, X, Enter, Backspace.
- Cycle-exact Gameboy CPU emulation. Each opcode is split into a few micro-operations (load value from memory, store it to register, etc.) and each micro-operation is run in a separate CPU cycle.
- Quite compatible (all the Blargg's tests are passed, although some game still doesn't work)
- GPU
- Joypad
- Timer
- Sound
- MBC1-5 support
- Battery saves
- Support for zipped ROMs
- ROM-based compatibility tests run from Maven
The Blargg's test ROMs are used for testing the compatibility. Tests can be launched from Maven using appropriate profile:
mvn clean test -Ptest-blargg
mvn clean test -Ptest-blargg-individual # for running "single" tests providing more diagnostic info
They are also part of the Travis-based CI.
The tests output (normally displayed on the Gameboy screen) is redirected to the stdout:
cpu_instrs
01:ok 02:ok 03:ok 04:ok 05:ok 06:ok 07:ok 08:ok 09:ok 10:ok 11:ok
Passed all tests
Coffee GB passes all the tests:
- cgb_sound
- cpu_instrs
- dmg_sound-2
- halt_bug
- instr_timing
- interrupt_time
- mem_timing-2
- oam_bug-2
The Mooneye GB emulator comes with a great set of test ROMs. They can be used to test the Coffee GB as well. Use -Ptest-mooneye profile:
mvn clean test -Ptest-mooneye
The default key bindings can be changed with the ~/.coffeegb.properties file. The file has following format:
btn_up=VK_UP
btn_down=VK_DOWN
btn_left=VK_LEFT
btn_right=VK_RIGHT
btn_a=VK_Z
btn_b=VK_X
btn_start=VK_ENTER
btn_select=VK_BACK_SPACE
The key list can be found in the KeyEvent JavaDoc.
- GameBoy CPU manual
- The Ultimate GameBoy talk
- Gameboy opcodes
- Nitty Gritty Gameboy cycle timing
- Video Timing
- BGB emulator --- good for testing / debugging, works fine with Wine
- The Cycle-Accurate Game Boy Docs
- Test ROMs - included in the src/test/resources/roms
- Pandocs
- Mooneye GB - an accurate emulator written in Rust, contains great ROM-based acceptance tests