epaperjs

v1.8.0

Published

3 years ago

Simple e-Paper display on a Raspberry Pi using Javascript and HTML

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samsonmking

Node.js library for easily creating an ePaper display on a Raspberry Pi using HTML and Javascript.

Render HTML DOM onto ePaper display
Simple and extensible Javascript and WebSocket API
Supports multiple Waveshare ePaper Displays
High performance, native c++ hardware access

Example weather station Example ereader gif

Working with the API

Create static/index.html. The contents of this webpage will be rendered onto the ePaper display.

<!DOCTYPE html>
<html lang="en">
    ...
    <body>
        <h1>Hello from ePaper.js</h1>
        <script>
            // connect to the WebSocket API
            const ws = new WebSocket('ws://localhost:8080');
            ws.addEventListener('open', () => {
                // draw contents of DOM onto ePaper display
                ws.send('render');
            });
        </script>
    </body>
</html>

From Node.js initialize ePaper.js. This does the following:

Creates a webserver that serves index.html from the static directory, or serves a page from an external web server
Loads index.html in a headless instance of Chromium, using Puppeteer
Creates a WebSocket API that the frontend can use to trigger a display refresh, or perform custom actions
Renders the contents of the browser DOM onto the ePaper display

const { init } = require('epaperjs');

init();

Additional Configuration

Additional Configuration Options

const { devices, init } = require('epaperjs');
init(devices.waveshare4in2, {
    webPort: 3000, // WebServer Port
    websocketPort: 8080, // WebSocket API Port
    staticDirectory: 'static', // Directory to serve frontend from
    skipWebServer: false, // If set to true will not create a local web server
    url: `http://localhost:3000/index.html`, // Initial URL to load
    enableDithering: true, // If set to true, a dithering algorithm will be applied to approximate mid-tones
});

Extend the server side WebSocket API

const { devices, init } = require('epaperjs');

const render = (page, ws) => {
    // Forward frontend console output to Node.js console
    page.onConsoleLog(console.log);

    // When recieving 'render' from frontend, update display
    ws.on('message', async (message) => {
        if (message === 'render') {
            await page.display();
        }
    });

    // forward keypresses to the frontend over WebSocket
    process.stdin.addListener('keypress', (key, data) => {
        if (data.name === 'left') {
            ws.send('left');
        }
        if (data.name === 'right') {
            ws.send('right');
        }
    });
};

init(devices.waveshare4in2, {}, render);

Examples
See the examples directory

weather-station: This creates and example weather station display
ereader: An ereader that reads epub files and uses the left and right keypresses to change pages
4gray: A demonstration of the 4gray capabilities
dithering: A demonstration of the dithering feature

Installation

Raspberry PI
Enable SPI

sudo raspi-config
# Choose Interfacing Options -> SPI -> Yes  to enable SPI interface
sudo reboot

Install Dependencies

# Install latest Node.js LTS
curl -sL install-node.now.sh/lts | sudo bash

sudo apt-get update

# Install wiringpi
wget https://project-downloads.drogon.net/wiringpi-latest.deb
sudo dpkg -i wiringpi-latest.deb
#You will get 2.52 information if you've installed it correctly
gpio -v

# Remaining dependencies
sudo apt-get install -y build-essential chromium-browser

Node.js
Install ePaper.js

npm install -S epaperjs

Supported Hardware

| Device | Black / White | 4 Gray | Dithering | | ------------------------------------------------------------------------------- | ------------- | ------ | --------- | | Waveshare 4.2" | ✅ | ✅ | B/W only | | Waveshare 7.5" v2 | ✅ | | ✅ | | Waveshare 3.7" hat | ✅ | ✅ | B/W only | | Waveshare 2.13" hat v2 | ✅ | | | | Waveshare 2.13" bc | ✅ | | ✅ | | Waveshare 2.7" | ✅ | | Partial |

Adding Support For Additional Displays

It's easy to extend ePaper.js to support additional Waveshare devices. Displays from other manufacturers should be possible to support as well, as long as there is a C / C++ driver available.

If you would like to request support for another display, please open an issue with the title 'Add support for <Device Make \ Model>'. If you're a developer and have extended support yourself, put up a pull request!

Feature Backlog

[x] Add support for portrait or landscape display (rotate 90 deg)
[ ] Add support for remaining Waveshare SPI ePaper displays
[x] Implement 4 Color Grayscale
[ ] Implement Red / White / Black Color Mode
[ ] Implement Yellow / White / Black Color Mode
[ ] Implement Partial Refresh

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