Control WS2812B strip on a Raspberry Pi

hello_ws2812.csproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp2.2</TargetFramework>
    <RootNamespace>hello_ws2812</RootNamespace>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="System.Device.Gpio" Version="0.1.0-prerelease*" />
    <PackageReference Include="Iot.Device.Bindings" Version="0.1.0-prerelease*" />
  </ItemGroup>

</Project>

Program.cs

using System;
using System.Device.Spi;
using System.Device.Spi.Drivers;
using System.Drawing;
using Iot.Device.Graphics;
using Iot.Device.Ws28xx;

namespace hello_ws2812
{
    class Program
    {
        private const int count = 30; 
        static void Main()
        {
            var settings = new SpiConnectionSettings(0, 0) {
                ClockFrequency = 2_400_000,
                Mode = SpiMode.Mode0,
                DataBitLength = 8
            };
            
            var spi = new UnixSpiDevice(settings);
            var device = new Ws2812b(spi, count);

            // Display basic colors for 5 sec
            BitmapImage image = device.Image;
            image.Clear();
            image.SetPixel(0, 0, Color.Orange);
            image.SetPixel(1, 0, Color.Red);
            image.SetPixel(2, 0, Color.Green);
            image.SetPixel(3, 0, Color.Blue);
            image.SetPixel(4, 0, Color.Yellow);
            image.SetPixel(5, 0, Color.Cyan);
            image.SetPixel(6, 0, Color.Magenta);
            image.SetPixel(7, 0, Color.FromArgb(unchecked((int)0xffff8000)));
            device.Update();
            System.Threading.Thread.Sleep(5000);
    
            // Chase some blue leds
            for(int i=0; i<10; i++)
            {
                image.Clear();
                for(int j=0; j<count; j++)
                {
                    image.SetPixel(j, 0, Color.LightBlue);
                    device.Update();
                    System.Threading.Thread.Sleep(10);
                    image.SetPixel(j, 0, Color.Blue);
                    device.Update();
                    System.Threading.Thread.Sleep(25);
                }
            }

            // Color Fade
            int r=255;
            int g=0;
            int b=0;

            while (! Console.KeyAvailable) {
                if(r > 0 && b == 0){
                    r--;
                    g++;
                }
                if(g > 0 && r == 0){
                    g--;
                    b++;
                }
                if(b > 0 && g == 0){
                    r++;
                    b--;
                }

                image.Clear(Color.FromArgb(r,g,b));
                device.Update();
                System.Threading.Thread.Sleep(10);
            }    


            image.Clear();
            device.Update();

            Console.WriteLine("Hello Pi!");
        }
    }
}

Where in the code does it bind to a specific GPIO pin?

I believe the iot library handles it based on given SpiConnectionSettings, so the code is:
var settings = new SpiConnectionSettings(0, 0) { ClockFrequency = 2_400_000, Mode = SpiMode.Mode0, DataBitLength = 8 };

Author's post with some more details on this scenario: https://jamesnaylor.dev/Posts/Read?id=pi-ws2812-with-net-core

I keep getting this error: 'UnixSpiDevice' is inaccessible due to its protection level

Hi @mindsgn. You might need to enable it in the boot configuration on your RaspberryPi. Add the following lines to /boot/config.txt on your device:

dtparam=spi=on
core_freq=250
core_freq_min=250

Also bear in mind that this code is hideously outdated and I think the GPIO support in .NET 5 is significantly different. When I get the time, I'll update this.

Hi @mindsgn, I ran into this same issue. To create a UnixSpiDevice, try

var spi = SpiDevice.Create(settings);

That should do it.

Can you dim them?

Can you dim them?

Yes, you just send darker colours. Black turns LEDs off.