AngularGB

Just another Gameboy emulator for the browser.

I spent a lot of time playing emulated handheld games on my family's computer and my smartphone. Retro gaming never felt "retro" to me, because they were almost everything I used to play, and they were a huge source of inspiration for me to become a software engineer.

Now, equipped with some Computer Science knowledge and an unhealthy amount of free time, I make this project as a tribute to the retro games that made my childhood.

Although this emulator can render and play simples Gameboy games, it is still very much incomplete and inaccurate. All suggestions and contributions are greatly appreciated!

Project overview

As mentioned in the title, AngularGB is a standard Angular application. However, the emulation core is written independently from Angular, most can be found inside folder src/models and should be easy to port to any other web front end framework.

Below is the way the current Gameboy component loads a decoded ROM bytes array:

public loadRom(rom: number[]): void {
    this.reset();
    if (rom === null) {
        return;
    }
    this.rom = rom;
    const mbc = getMbc(rom);
    this.speaker = new GbSpeaker(48000);
    this.gameboy = new Gameboy(mbc, this.lcd, this.speaker);
    this.resume();
}

The Gameboy() constructor requires one GbMbc, one Lcd and one Speaker object, representing the cartridge's MBC, the LCD screen and the Speaker. The correct GbMbc type - based on the ROM's header - can be retrieved from getMbc(), while the two classes CanvasLcd and GbSpeaker provide concrete implementation for Lcd and Speaker interface to respectively output graphic and audio to an HTML5 Canvas and the device's speaker. Feel free to extend these two interfaces if extra functionalities are needed.

Gameboy allows either running instruction by instruction, or frame by frame. The app maintains a healthy 60 FPS by using setInterval() to schedule a new frame every 1/60 of a second.

Initially, I used Ant Design for Angular to implement the UI, which included a handful of debug tools such as disassembler, CPU/memory/PPU state trackers, etc... However, bundling this library with the core emulation logic somehow slowed the emulator down significantly. Because of that, I removed all usage of Ant Design - along with the debug tools - and rewrote the UI with Bootstrap 5's CSS. The debug tools can still be found in the folder src/app/components/debug, and can still totally work with a Gameboy Input(), but remember that building the project in production configuration will result in the aforementioned slowdown.

How to run

To install the project:

npm install

To run development server:

ng serve

To run Jasmine test suite:

ng test

Current status

Supported features

All instructions are implemented except for STOP.
No DMA Transfer glitch or Wave RAM glitch.
Memory timing is not accurate for instructions that do both read and write (would be impossible since this condition requires the emulator to run cycle-by-cycle, not instruction-by-instruction).
ROM-only MBC, MBC1 and MBC2 are supported. This allows the emulator to run a large number of games, but leaves out games with other MBC cartridge types, notably Pokemon Red/Blue which use MBC3.
Audio is not implemented correctly. It works fine with some games (Link's Awakening and Tetris) but breaks uncontrollably with other (Super Mario Land, Dr. Mario). Audio also lags behind graphic noticeably after a while. For now, it's best to disable audio for the best frame rate and experience.

Tests

Blargg's test ROMs

Test	Result
cpu_instrs	OK
dmg_sound	Failed 03 (test 11), 09 (test 01), 10 (test 01), 12 (test 01)
instr_timing	OK
interrupt_time	Failed (`00 00 00 00 08 0D 00 00 00 00 08 0D 7F8F4AAF`)
mem_timing	Failed 03 (test 01)
mem_timing-2	Failed 03 (test 01)
oam_bug	Failed 01 (test 02), 02 (test 02), 04 (test 03), 05 (test 02), 07 (test 01), 08 (test 02)
halt_bug	Failed

dmg-acid2 by Matt Currie

License

GNU General Public License v3.0

tranHieuDev23/AngularGB