OnaNES (Oh No Another NES Emulator)

In Javascript !

This is my implementation of the NES console, which emulates both the original CPU and PPU.

This git repo comes without a frontend as I wanted it to be as bare as possible. I started implementing a UI using React.js, you can find the source code here.

Getting Started

Installing

NPM

npm install nes-emulator

Local

Clone the repo and

npm install
npm run build

How to Use

The library uses an observer pattern to signal events (frames ready, reset, pause ...).

Here's an example of how to use this library.

import { Console } from "nes-emulator";

class NES {
    constructor() {
        this.console = new Console();

        // Will notify `this.notify` upon events
        this.console.addObserver( this );

        // Here romData is the content of a .nes ROM
        this.console.loadROM( `romData` );
        this.console.start();
    }

    notify(t, e) {
        switch (t) {
            case 'frame-ready': {
                // Draw the frame using `e` (Uint8Array)
            }
        }
    }

}

Examples

Sketchfab Viewer API (http://grun7.com/sketchfab-viewer-api-nes/)

This was made only for fun, to show it is possible to make this emulator run and displayed on a 3D model. It uses Sketchfab and its viewer API.

Demo with React (https://onanes.herokuapp.com/)

UI using ReactJS

Features

Done

• Fully functional CPU
• Functional PPU
• UXROM, NROM, MMC1, MMC3 mappers
• Save/Load

In Progress

• Additional mappers
• Sound

TODO

The emulator is missing features such as

• Tests
• Make list of playable games

And needs improvement for

• Cycle accurate CPU
• Some PPU glitches

API Documentation

TODO WIP

Signals triggered by the Console

frame-ready

Fired at a 60 fps rate when a frame is ready, provides a 256x240x4 byte array containing the RGB colors to display.

nes-reset

Fired when a game is loaded and the console restarts.

Contributing

I'm still actively working on it but would welcome your PRs. Do not hesitate to fork the repository and h4ck around.

Acknowledgments

Special thanks for the amazing http://nesdev.com/ and all their technical resources without which this project would not have been possible.

License

NES Emulator
Copyright (C) 2018 Frédéric Cambon

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.