Nerves.Neopixel

Drive WS2812B "NeoPixel" RGB LED strips from a Raspberry Pi using Elixir!

This project was designed to make it easy to drive a string of AdaFruit NeoPixels from a Raspberry Pi using Nerves. The code would probably also work outside of Nerves with minor modifications to the Makefile, if you so desire.

Installation

Add it to your list of dependencies in mix.exs:

```elixir
def deps do
  [{:nerves_neopixel, "~> 0.3.2"}]
end
```

If you've cloned the nerves_neopixel repository, be sure to check out the rpi_ws281x submodule:

$ git submodule init
$ git submodule update

Connections

Only a subset of GPIO pins on the Raspberry Pis can control the NeoPixels. See GPIO Usage for details. Additionally, since the Raspberry Pi has 3.3V I/O outputs and the NeoPixels require 5V I/O input, you'll need a level shifter to convert between voltages.

You can read more about using NeoPixels with Nerves in my blog post about the project.

Usage

Supervision trees and an Elixir Port are used to maintain fault-tolerance when interfacing with the low-level driver, which is written in C. To drive an NeoPixel strip, you just have to configure which GPIO pin to use and how many NeoPixels are in the strip by passing the configuration settings to Nerves.NeoPixel.start_link.

Once the process is started, you can call the Nerves.Neopixel.render function with a list of tuples representing the pixel data, along with the overall intensity, as follows:

alias Nerves.Neopixel
ch0_config = [pin: 18, count: 3]
ch1_config = [pin: 19, count: 3]
{:ok, pid} = Neopixel.start_link(ch0_config, ch1_config)

channel = 0
intensity = 127
data = [
  {255, 0, 0},
  {0, 255, 0},
  {0, 0, 255},
]
Neopixel.render(channel, {intensity, data})