epd4in2

A Node.js package for the 4.2inch e-Paper waveshare display on a Raspberry Pi 2/3/zero, forked from williwasser's epd7x5 Node.js package

Link to waveshare wiki

Dependencies

1. WiringPi for GPIO access of Raspberry Pi
2. libgd2 for text output and drawing

Installation

Enable the SPI interface on Raspberry Pi: sudo raspi-config

WiringPi: follow installation on wiringpi.com

libgd2: sudo apt-get install libgd2-dev # libgd

epd4in2: npm install epd4in2

Usage example

const epd = require('epd4in2')
 
const font = '/home/pi/bauhaus.ttf';
const fontSize = 26
 
async function refreshDisplay(message) {
  await epd.init();
  let img = await epd.getImageBuffer('landscape');
 
  img.filledRectangle(
    Math.round(10), Math.round(10),
    Math.round(80), Math.round(20),
    epd.colors.white)
 
  let [xll, yll, xlr, ylr, xur, yur, xul, yul] = img.stringFTBBox(epd.colors.white, font, fontSize, 0, 0, 0, message)
 
  // Center the message
  img.stringFT(epd.colors.white, font, fontSize, 0,
    Math.round(img.width / 2 - (xur - xul) / 2),
    Math.round(img.height / 2 + (yll - yul) / 2),
    message)
 
  img.negate()
 
  await epd.displayImageBuffer(img);
  await epd.sleep();
}
 
 
refreshDisplay("Hello World!")
 

The module exports the following functions and constants:

Functions:

epd.init()

epd.getImageBuffer('landscape') Use landscape to get a buffer oriented in landscape mode.

epd.displayImageBuffer(img)

epd.clear() Equivalent to push a white image

epd.sleep() Put the display in sleep mode. init is required to come back to operations.

Constants:

epd.colors.white

epd.colors.black

epd.width

epd.height

gd namespace for access of functions on the gd object:

epd.gd

example: epd.gd.createFromFile(path) to open an image

Documentation of node-gd functions can be found here

License

Apache 2.0