Swiftpack.co - Package - uraimo/WS281x.swift


A Swift library for WS281x/NeoPixel (WS2811,WS2812,WS2812B,WS2813) RGB led strips, rings, sticks, matrices and more

Linux-only Swift 4 compatible License: MIT


This library simplifies the configuration of series of WS281x leds (WS2811, WS2812, WS281x), sometimes marketed as NeoPixels (or NeoMatrix for led matrices), regardless of the form in which they are sold: strips, matrices, rings, etc...

You will be able to set the color of individual pixels (with both sequential and matrix coordinates) or set them in bulk with a single call (faster, recommended for smoother animations). Click here or here for two real-time gifs that show an example what you can do with this library.


First of all an hardware note, WS281x leds are 3-pins 5V devices (Vcc,DataIN,GND) but most of the times can tollerate a 3.3V DataIN signal like the one produced by the RaspberryPi's gpio pins (and other ARM board's gpios).

If you notice that your leds are flickering or not too bright while connecting them directly to a gpio, you could need a level shifter/converter/translator for you data pin. There are a lot of different ways (with different performance) to translate a 3.3V signal to a 5V one, but the most cost effective way to solve this specific problem is maybe just to buy a simple level converter like this one from SparkFun. It works perfectly and you just need to solder a pin header and you are ready to go.

For more hardware information on WS281x/NeoPixel leds, check out the Adafruit's Ɯberguide.

Now, for the software side, suppose we are using a strip with 60 WS2812B leds, the first thing we need to do is obtain an instance of PWMOutput from SwiftyGPIO and use it to initialize the WS281x object:

import SwiftyGPIO
import WS281x

let pwms = SwiftyGPIO.hardwarePWMs(for:.RaspberryPi2)!
let pwm = (pwms[0]?[.P18])!

let numberOfLeds = 60

let w = WS281x(pwm, 
               type: .WS2812B,
               numElements: numberOfLeds)

We'll then need to specify the number of leds and the type of the leds we are using (either .WS2811, .WS2812 or .WS2812B), the library will use the type to determine the correct signaling timing for these leds.

Let's start clearing all the leds in the strip, setting them with the rgb color #000000:

var initial = [UInt32](repeating:0x0, count: numberOfLeds)



With setLeds we are configuring the strip with an array of 60 32 bits elements that contain the pixel 24bits colors in the format 0x00RRGGBB. Once done, we call start() to send the signal and then wait() for the configuration of the strip to complete.

We can then set individual pixel along the strip:

w.setLed(10, r: 0xF0, g: 0, b: 0)

Or if we had a matrix we could have also used two specific additional methods that use two different 2D coordinate schemes.

Your matrix could be connected differently from these two, do some test setting individual pixels with setLed() to understand how the leds are connected or use the snake effect that scrolls through the sequence from the beginning to the last element.

Let's set the led at (4,4) for matrices where each row starts with the (row-1)*width element in the sequence (e.g. Nulsom Rainbow Matrix) as show here:

  0  1  2  3
  4  5  6  7
  8  9  10 11
  12 13 14 15

In this case we'll use setLedAsMatrix:

w.setLedAsMatrix(x: 4, y: 4, width: matrixWidth, r: 0, g: 0, b: 0xF0)

Now, let0s set the led at (5,2) for matrices where each row is connetted to the last element of the preceding row (e.g. Pimoroni UnicornHat) like this:

  3  2  1  0
  4  5  6  7
  11 10 9  8
  12 13 14 15

In this case we'll use setLedAsSequentialMatrix:

w.setLedAsSequentialMatrix(x: 5, y: 2, width: matrixWidth, r: 0, g: 0, b: 0xF0)

If neither method set the pixels of your matrix in the right position just use setLed to roll you own implementation or perform bulk setLeds (as you'll see in the example this is what I normally do too)

Remember to always call start() once you have invoked one of the setLed* methods to send the signal that will configure the sequence of WS2812 leds and to use wait() to wait for the actuation of the configuration to complete (needed only when you want to be sure that the configuration will be applied in its entirety, e.g. when clearing the leds before new effects, or when you want to shut down the led strip cleanly before exiting).

Adafruit, as usual, has a very detailed post on leds arragement in NeoPixel matrices.

Once you are done (or even in a defer block) remember to clean up all the temporary PWM settings that were needed for this library with:


Supported Boards

Every board supported by SwiftyGPIO with pattern-based PWM signal generator, at the moment only RaspberryPis.

And to use this library, you'll need Swift 3.x/4.x.

The example below will use a RaspberryPi 2 board but you can easily modify the example to use one the the other supported boards, a full working demo projects for the RaspberryPi2 is available in the Examples directory.


Please refer to the SwiftyGPIO readme for Swift installation instructions.

Once your board runs Swift, if your version support the Swift Package Manager, you can simply add this library as a dependency of your project and compile with swift build:

  let package = Package(
      name: "MyProject",
      dependencies: [
    .Package(url: "https://github.com/uraimo/WS281x.swift.git", majorVersion: 2),

The directory Examples contains sample projects that uses SPM, compile it and run the sample with ./.build/debug/TestWS2812B.

If SPM is not supported, you'll need to manually download the library and its dependencies:

wget https://raw.githubusercontent.com/uraimo/WS281x.swift/master/Sources/WS281x.swift https://raw.githubusercontent.com/uraimo/SwiftyGPIO/master/Sources/SwiftyGPIO.swift https://raw.githubusercontent.com/uraimo/SwiftyGPIO/master/Sources/Presets.swift https://raw.githubusercontent.com/uraimo/SwiftyGPIO/master/Sources/PWM.swift https://raw.githubusercontent.com/uraimo/SwiftyGPIO/master/Sources/Mailbox.swift  https://raw.githubusercontent.com/uraimo/SwiftyGPIO/master/Sources/SunXi.swift  

And once all the files have been downloaded, create an additional file that will contain the code of your application (e.g. main.swift). When your code is ready, compile it with:

swiftc *.swift

The compiler will create a main executable.

Frequently Asked Questions

1. How many leds I will be able to control?

The update frequency and the power consumption are the limiting factors. As the number of leds grows, it takes progressively more time to configure all the connected leds and the power consumption increases. While you can solve the power problem connecting the strip to an external 5V power adapter instead of using the board's 5V/GND pins, the update frequency problem is related to the timing characteristics of the WS281x protocol.

You will be able to use strips with around 400-500 leds without issues, but then you'll start to see progressively diminishing refresh times that could not be appropriate for fast animations. How many leds can the library drive? This depends on how much sequential memory the VideoCore subsystem is able to allocate, there have been reports of people using similar libraries being able to control more than 3000 leds from a RaspberryPi1.

2. Why the library does not appear to work when I'm using the RaspberryPI audio output?

The PWM hardware that this library uses is shared with the audio output, you can't use them both simultaneously and some OSes could enable the audio port by default.

You could need (ATM, not needed for Raspbian and Ubuntu) to black-list the audio module adding to /etc/modprobe.d/snd-blacklist.conf:

blacklist snd_bcm2835

3. Does this work with APA102/DotStar leds?

No, since APA102 leds work with a standard SPI connection.

4. Why two enums values for the WS2812B

WorldSemi released an updated version of the WS2812B at the beginning of 2017, that requires a longer reset delay, for more information read this. If your WS2812 leds don't appear to work, try selecting the enum value for the newer model.


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