Added Support for SK6812-Strips (#1709)

Co-authored-by: NJose Perez Rodriguez <joperezr@microsoft.com>

src/devices/Ws28xx/BitmapImageNeo4.cs

+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Drawing;
+using Iot.Device.Graphics;
+
+namespace Iot.Device.Ws28xx
+{
+    internal class BitmapImageNeo4 : BitmapImage
+    {
+        private const int BytesPerComponent = 3;
+        private const int BytesPerPixel = BytesPerComponent * 4;
+
+        // The Neo Pixels require a 50us delay (all zeros) after. Since Spi freq is not exactly
+        // as requested 100us is used here with good practical results. 100us @ 2.4Mbps and 8bit
+        // data means we have to add 30 bytes of zero padding.
+        private const int ResetDelayInBytes = 30;
+
+        // This field defines the count within the lookup table. The length correlates to the possible values of a single byte.
+        private const int LookupCount = 256;
+
+        private static readonly byte[] _lookup = new byte[LookupCount * BytesPerComponent];
+
+        static BitmapImageNeo4()
+        {
+            for (int i = 0; i < LookupCount; i++)
+            {
+                int data = 0;
+                for (int j = 7; j >= 0; j--)
+                {
+                    data = (data << 3) | 0b100 | ((i >> j) << 1) & 2;
+                }
+
+                _lookup[i * BytesPerComponent + 0] = unchecked((byte)(data >> 16));
+                _lookup[i * BytesPerComponent + 1] = unchecked((byte)(data >> 8));
+                _lookup[i * BytesPerComponent + 2] = unchecked((byte)(data >> 0));
+            }
+        }
+
+        public BitmapImageNeo4(int width, int height)
+                            : base(new byte[width * height * BytesPerPixel + ResetDelayInBytes], width, height, width * BytesPerPixel)
+        {
+        }
+
+        public override void SetPixel(int x, int y, Color c)
+        {
+            // Alpha is used as white.
+            var offset = y * Stride + x * BytesPerPixel;
+            Data[offset++] = _lookup[c.G * BytesPerComponent + 0];
+            Data[offset++] = _lookup[c.G * BytesPerComponent + 1];
+            Data[offset++] = _lookup[c.G * BytesPerComponent + 2];
+            Data[offset++] = _lookup[c.R * BytesPerComponent + 0];
+            Data[offset++] = _lookup[c.R * BytesPerComponent + 1];
+            Data[offset++] = _lookup[c.R * BytesPerComponent + 2];
+            Data[offset++] = _lookup[c.B * BytesPerComponent + 0];
+            Data[offset++] = _lookup[c.B * BytesPerComponent + 1];
+            Data[offset++] = _lookup[c.B * BytesPerComponent + 2];
+            Data[offset++] = _lookup[c.A * BytesPerComponent + 0];
+            Data[offset++] = _lookup[c.A * BytesPerComponent + 1];
+            Data[offset++] = _lookup[c.A * BytesPerComponent + 2];
+        }
+    }
+}

src/devices/Ws28xx/README.md

-# Ws28xx LED drivers
+# Ws28xx / SK6812 LED drivers
 
-This binding allows you to update the RGB LEDs on Ws28xx and based strips and matrices.
+This binding allows you to update the RGB LEDs on Ws28xx / SK6812 and based strips and matrices.
 
-To see how to use the binding in code, see the [sample](samples/Program.cs).
+To see how to use the binding in code, see the [sample](samples/Ws28xx_Samples/Program.cs).
 
 ## Documentation
 
 * WS2812B: [Datasheet](https://cdn-shop.adafruit.com/datasheets/WS2812B.pdf)
 * WS2808: [Datasheet](https://datasheetspdf.com/pdf-file/806051/Worldsemi/WS2801/1)
+* SK6812: [Datasheet](https://cdn-shop.adafruit.com/product-files/2757/p2757_SK6812RGBW_REV01.pdf)
 * [Neo pixels guide](https://learn.adafruit.com/adafruit-neopixel-uberguide)
 * [Neo pixels x8 stick](https://www.adafruit.com/product/1426)
 
 ## Board
 
-### Neo pixels
+### Neo pixels / SK6812
 
 ![Raspberry Pi Breadboard diagram](rpi-neo-pixels_bb.png)
 
@@ -44,7 +45,7 @@ SpiConnectionSettings settings = new(0, 0)
 using SpiDevice spi = SpiDevice.Create(settings);
 
 Ws28xx neo = new Ws2808(spi, count);
-//Ws28xx neo = new Ws2812b(spi, Count);
+// Ws28xx neo = new Ws2812b(spi, Count);
 
 while (true)
 {
@@ -67,17 +68,27 @@ void Rainbow(Ws28xx neo, int count, int iterations = 1)
 }
 ```
 
+***Note:***
+
+Using the SK6812 is almost the same, but the alpha channel of the color is used for the white LED. This means that the predefined color definitions (like ```System.Drawing.Color.Red```) will not work correctly as they have the alpha channel set to 255 (0xFF). That will turn the white LED always on. See the [sample](samples/SK6812_Samples/Programs.cs) for the main differences to the above code.
+Because ```System.Drawing.Color``` is a readonly struct, it's not possible to change the any channel directly. In order to correctly set Red, use ```Color.FromArgb(0, 255, 0, 0)```. For setting the white LED, use ```Color.FromArgb(255, 0, 0, 0)```. It's also possible to use an existing definition and remove the white channel like this:
+
+```csharp
+var color = Color.HotPink;
+var newColor = Color.FromArgb(0, color.R, color.G, color.B);
+```
+
 ## Binding Notes
 
 ### Raspberry Pi setup (/boot/config.txt)
 
-* Make sure spi is enabled
+* Make sure SPI is enabled
 
 ```text
 dtparam=spi=on
 ```
 
-* Make sure SPI don't change speed fix the core clock:
+* To make sure SPI doesn't change speed fix the core clock:
 
 ```text
 core_freq=250

src/devices/Ws28xx/Sk6812.cs

+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Device.Spi;
+
+namespace Iot.Device.Ws28xx
+{
+    /// <summary>
+    /// Represents the SK6812 Driver.
+    /// </summary>
+    /// <seealso cref="Iot.Device.Ws28xx.Ws28xx" />
+    public class Sk6812 : Ws28xx
+    {
+        /// <summary>
+        /// Gets the default SPI clock frequency.
+        /// </summary>
+        /// <value>
+        /// The default SPI clock frequency used for SK6812-LED-Strips.
+        /// </value>
+        /// <remarks>This frequency defines how fast the data will be put on the line. The SK6812-strip requires a speed of 1.25 kHz.
+        /// A single byte takes 1.2 µs for the transfer, the value for a single LED of 32 bit amounts to 38.4 µs.
+        /// </remarks>
+        public static int DefaultSpiClockFrequency => 2_400_000;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Sk6812"/> class.
+        /// </summary>
+        /// <param name="spiDevice">The spi device.</param>
+        /// <param name="width">The width.</param>
+        /// <param name="height">The height.</param>
+        public Sk6812(SpiDevice spiDevice, int width, int height = 1)
+            : base(spiDevice, new BitmapImageNeo4(width, height))
+        {
+        }
+    }
+}

src/devices/Ws28xx/Ws28xx.sln

 
 Microsoft Visual Studio Solution File, Format Version 12.00
-# Visual Studio 15
-VisualStudioVersion = 15.0.26124.0
+# Visual Studio Version 16
+VisualStudioVersion = 16.0.31729.503
 MinimumVisualStudioVersion = 15.0.26124.0
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "samples", "samples", "{B2C3D1C3-4F59-4544-982C-E205F522DF27}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Ws28xx.Samples", "samples\Ws28xx.Samples.csproj", "{D97F0DC4-777E-4F1A-BF18-A63DA22707ED}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Ws28xx.Samples", "samples\Ws28xx_Samples\Ws28xx.Samples.csproj", "{D97F0DC4-777E-4F1A-BF18-A63DA22707ED}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Ws28xx", "Ws28xx.csproj", "{D909238E-13C4-45C4-B044-CCBB08B51647}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Ws28xx", "Ws28xx.csproj", "{D909238E-13C4-45C4-B044-CCBB08B51647}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Sk6812.Samples", "samples\Sk6812_Samples\Sk6812.Samples.csproj", "{76D2B9B1-CBDE-445C-BE6D-B5C5C1754192}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -18,9 +20,6 @@ Global
 		Release|x64 = Release|x64
 		Release|x86 = Release|x86
 	EndGlobalSection
-	GlobalSection(SolutionProperties) = preSolution
-		HideSolutionNode = FALSE
-	EndGlobalSection
 	GlobalSection(ProjectConfigurationPlatforms) = postSolution
 		{D97F0DC4-777E-4F1A-BF18-A63DA22707ED}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
 		{D97F0DC4-777E-4F1A-BF18-A63DA22707ED}.Debug|Any CPU.Build.0 = Debug|Any CPU
@@ -46,8 +45,27 @@ Global
 		{D909238E-13C4-45C4-B044-CCBB08B51647}.Release|x64.Build.0 = Release|Any CPU
 		{D909238E-13C4-45C4-B044-CCBB08B51647}.Release|x86.ActiveCfg = Release|Any CPU
 		{D909238E-13C4-45C4-B044-CCBB08B51647}.Release|x86.Build.0 = Release|Any CPU
+		{76D2B9B1-CBDE-445C-BE6D-B5C5C1754192}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{76D2B9B1-CBDE-445C-BE6D-B5C5C1754192}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{76D2B9B1-CBDE-445C-BE6D-B5C5C1754192}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{76D2B9B1-CBDE-445C-BE6D-B5C5C1754192}.Debug|x64.Build.0 = Debug|Any CPU
+		{76D2B9B1-CBDE-445C-BE6D-B5C5C1754192}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{76D2B9B1-CBDE-445C-BE6D-B5C5C1754192}.Debug|x86.Build.0 = Debug|Any CPU
+		{76D2B9B1-CBDE-445C-BE6D-B5C5C1754192}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{76D2B9B1-CBDE-445C-BE6D-B5C5C1754192}.Release|Any CPU.Build.0 = Release|Any CPU
+		{76D2B9B1-CBDE-445C-BE6D-B5C5C1754192}.Release|x64.ActiveCfg = Release|Any CPU
+		{76D2B9B1-CBDE-445C-BE6D-B5C5C1754192}.Release|x64.Build.0 = Release|Any CPU
+		{76D2B9B1-CBDE-445C-BE6D-B5C5C1754192}.Release|x86.ActiveCfg = Release|Any CPU
+		{76D2B9B1-CBDE-445C-BE6D-B5C5C1754192}.Release|x86.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
 	EndGlobalSection
 	GlobalSection(NestedProjects) = preSolution
 		{D97F0DC4-777E-4F1A-BF18-A63DA22707ED} = {B2C3D1C3-4F59-4544-982C-E205F522DF27}
+		{76D2B9B1-CBDE-445C-BE6D-B5C5C1754192} = {B2C3D1C3-4F59-4544-982C-E205F522DF27}
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {F452F127-C7D8-4D14-9484-B23E8F0C3468}
 	EndGlobalSection
-EndGlobal
\ No newline at end of file
+EndGlobal

src/devices/Ws28xx/samples/Sk6812_Samples/Program.cs

+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Device.Spi;
+using System.Drawing;
+using System.Threading;
+using Iot.Device.Graphics;
+using Iot.Device.Ws28xx;
+
+// Configure the count of pixels
+const int Count = 8;
+Console.Clear();
+
+SpiConnectionSettings settings = new(0, 0)
+{
+    ClockFrequency = Sk6812.DefaultSpiClockFrequency,
+    Mode = SpiMode.Mode0,
+    DataBitLength = 8
+};
+using SpiDevice spi = SpiDevice.Create(settings);
+
+Sk6812 neo = new Sk6812(spi, Count);
+
+Console.CancelKeyPress += (o, e) =>
+{
+    BitmapImage img = neo.Image;
+    img.Clear();
+    neo.Update();
+    Console.Clear();
+};
+
+while (true)
+{
+    Color4Wipe(neo, Color.White, Count);
+    Color4Wipe(neo, Color.Red, Count);
+    Color4Wipe(neo, Color.Green, Count);
+    Color4Wipe(neo, Color.Blue, Count);
+
+    Theatre4Chase(neo, Color.White, Count);
+    Theatre4Chase(neo, Color.Red, Count);
+    Theatre4Chase(neo, Color.Green, Count);
+    Theatre4Chase(neo, Color.Blue, Count);
+
+    Rainbow4(neo, Count);
+    Rainbow4Cycle(neo, Count);
+    TheaterChase4Rainbow(neo, Count);
+}
+
+void Color4Wipe(Sk6812 neo, Color color, int count)
+{
+    BitmapImage img = neo.Image;
+    for (var i = 0; i < count; i++)
+    {
+        img.SetPixel(i, 0, color);
+        neo.Update();
+        Thread.Sleep(100);
+    }
+}
+
+void Theatre4Chase(Ws28xx neo, Color color, int count, int iterations = 10)
+{
+    BitmapImage img = neo.Image;
+    for (var i = 0; i < iterations; i++)
+    {
+        for (var j = 0; j < 3; j++)
+        {
+            for (var k = 0; k < count; k += 3)
+            {
+                img.SetPixel(j + k, 0, color);
+            }
+
+            neo.Update();
+            Thread.Sleep(100);
+            for (var k = 0; k < count; k += 3)
+            {
+                img.SetPixel(j + k, 0, Color.FromArgb(0, 0, 0, 0));
+            }
+        }
+    }
+}
+
+Color Wheel4(int position)
+{
+    if (position < 85)
+    {
+        return Color.FromArgb(0, position * 3, 255 - position * 3, 0);
+    }
+    else if (position < 170)
+    {
+        position -= 85;
+        return Color.FromArgb(0, 255 - position * 3, 0, position * 3);
+    }
+    else
+    {
+        position -= 170;
+        return Color.FromArgb(0, 0, position * 3, 255 - position * 3);
+    }
+}
+
+void Rainbow4(Sk6812 neo, int count, int iterations = 1)
+{
+    BitmapImage img = neo.Image;
+    for (var i = 0; i < 255 * iterations; i++)
+    {
+        for (var j = 0; j < count; j++)
+        {
+            img.SetPixel(j, 0, Wheel4((i + j) & 255));
+        }
+
+        neo.Update();
+        Thread.Sleep(50);
+    }
+}
+
+void Rainbow4Cycle(Ws28xx neo, int count, int iterations = 1)
+{
+    BitmapImage img = neo.Image;
+    for (var i = 0; i < 255 * iterations; i++)
+    {
+        for (var j = 0; j < count; j++)
+        {
+            img.SetPixel(j, 0, Wheel4(((int)(j * 255 / count) + i) & 255));
+        }
+
+        neo.Update();
+        Thread.Sleep(50);
+    }
+}
+
+void TheaterChase4Rainbow(Ws28xx neo, int count)
+{
+    BitmapImage img = neo.Image;
+    for (var i = 0; i < 255; i++)
+    {
+        for (var j = 0; j < 3; j++)
+        {
+            for (var k = 0; k < count; k += 3)
+            {
+                img.SetPixel(k + j, 0, Wheel4((k + i) % 255));
+            }
+
+            neo.Update();
+            System.Threading.Thread.Sleep(100);
+
+            for (var k = 0; k < count; k += 3)
+            {
+                img.SetPixel(k + j, 0, Color.FromArgb(0, 0, 0, 0));
+            }
+        }
+    }
+}

src/devices/Ws28xx/samples/Sk6812_Samples/Sk6812.Samples.csproj

+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net5.0</TargetFramework>
+  </PropertyGroup>
+  <ItemGroup>
+    <ProjectReference Include="../../Ws28xx.csproj" />
+  </ItemGroup>
+</Project>
\ No newline at end of file

src/devices/Ws28xx/samples/Ws28xx.Samples.csproj → src/devices/Ws28xx/samples/Ws28xx_Samples/Ws28xx.Samples.csproj

@@ -4,6 +4,6 @@
     <TargetFramework>$(DefaultSampleTfms)</TargetFramework>
   </PropertyGroup>
   <ItemGroup>
-    <ProjectReference Include="../Ws28xx.csproj" />
+    <ProjectReference Include="../../Ws28xx.csproj" />
   </ItemGroup>
 </Project>
\ No newline at end of file