WS2812 | Dev Center

WS2812

Latest Version: 3.0.0

This library allows an imp to drive WS2812 and WS2812B LEDs. The WS2812 is an all-in-one RGB LED with integrated shift register and constant-current driver. The parts are daisy-chained, and a proprietary one-wire protocol is used to send data to the chain of LEDs. Each pixel is individually addressable and this allows the part to be used for a wide range of effects animations.

Some example hardware that uses the WS2812 or WS2812B:

You can view the latest version of the library’s source code on GitHub. Click here to see information on other versions of this library.

To add this library to your project, add #require "WS2812.class.nut:3.0.0" to the top of your device code

Hardware

WS2812s require a 5V power supply and logic, and each pixel can draw up to 60mA when displaying white in full brightness, so be sure to size your power supply appropriately. Undersized power supplies (lower voltages and/or insufficient current) can cause glitches and/or failure to produce and light at all.

Because WS2812s require 5V logic, you will need to shift your logic level to 5V. A sample circuit can be found below using Adafruit’s 4-channel Bi-directional Logic Level Converter:

WS2812 Circuit

Warning We do not recommend using the imp005 with WS2812s. Unlike the imp001, imp002, imp003 and imp004m, the imp005 does not use DMA for SPI data transfers. Instead, each byte is written out individually, and this means there will always be a small gap between each byte. As a result, the LEDs may not work as expected and the performance of other operations, such as Agent/Device communications, are blocked when the draw() method is called.

Class Usage

All public methods in the WS2812 class return this, allowing you to easily chain multiple commands together:

pixels
    .set(0, [255,0,0])
    .set(1, [0,255,0])
    .fill([0,0,255], 2, 4)
    .draw();

Constructor: WS2812(spi, numberOfPixels[, draw])

Instantiate the class with a pre-configured SPI object and the number of pixels that are connected. The SPI object will be configured by the constructor. An optional third parameter can be set to control whether the class will draw an empty frame on initialization. The default value is true.

#require "ws2812.class.nut:3.0.0"

// Select the SPI bus
spi <- hardware.spi257;

// Instantiate LED array with 5 pixels
pixels <- WS2812(spi, 5);

Class Methods

set(index, color)

The set() method changes the color of a particular pixel in the frame buffer. The color is passed as as an array of three integers between 0 and 255 representing [red, green, blue].

Note The set() method does not output the changes to the pixel strip. After setting up the frame, you must call draw() (see below) to output the frame to the strip.

// Set and draw a pixel
pixels.set(0, [127,0,0]).draw();

fill(color[, start][, end])

The fill() methods sets all pixels in the specified range to the desired color. If no range is selected, the entire frame will be filled with the specified color.

Note The fill() method does not output the changes to the pixel strip. After setting up the frame, you must call draw() (see below) to output the frame to the strip.

// Turn all LEDs off
pixels.fill([0,0,0]).draw();

// Set half the array red
// and the other half blue
pixels
    .fill([100,0,0], 0, 2)
    .fill([0,0,100], 3, 4)
    .draw();

draw()

The draw() method draws writes the current frame to the pixel array (see examples above).

Release History

The Electric Imp Dev Center documents the latest version of the library. For past versions, please see the Electric Imp public GitHub repos listed below.

Version	Source Code	Notes
1.0.2	GitHub	Initial release
2.0.0	GitHub	Major API change: writePixel() is now set(); writeFrame() is now draw(); clearFrame() removed; fill() added; configure() added
2.0.1	GitHub	Minor code update
2.0.2	GitHub	Minor code update: out-of-range values no longer throw an error but are put in range
3.0.0	GitHub	Add support for imp003 SPI timings; remove configure() method as constructor now auto-configures SPI

License

The WS2812 class is licensed under the MIT License.