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SharpPiLed

An alternative take on hzeller's rpi-rgb-led-matrix C# binding.

We use (a fork of) his library as a submodule, but add our own interpretation of a C# binding for .NET Core on top.

First of all, please make sure you read and understand the documentation of the original native library rpi-rgb-led-matrix.

This project is simply a (slightly opinionated) .NET Core wrapper around that library, so I strongly suggest to get the native examples running first to make sure your LED panel works as expected and you figured out your led-row-addr-type and led-multiplexing settings as well as potentially required muxer settings for your panel type before attempting to control your panel from .NET with this wrapper.

Be aware that this is for .NET Core, and .NET Core currently only supports ARMv7 CPU's, so this will not work on a Raspberry Pi Zero or Zero W.

Using SharpPiLed

Adding SharpPiLed will be as easy as dotnet add package SharpPiLed to your .NET Core project.

Note: This package is not published yet and is still work in progress. For the time being please compile it on your Pi.

Then you create a LedMatrix instance, configured with your LedMatrixOptions, get hold of your Canvas and draw onto it:

var matrix = new LedMatrix(new LedMatrixOptions(), args);
var canvas = matrix.CreateOffscreenCanvas();

// Red line starting top left going downwards and to the right
canvas.DrawLine(1, 1, 16, 16, new Color(255, 0,0));

// At the time of writing not yet sure what this does. Need to
// figure that out ;) But its required for the panel to show sth.
matrix.SwapOnVsync(canvas);

Examples

See the Examples documentation.

Configuration

The LedMatrixOptions object exposes all settings of the library. The settings can also be configured via command line arguments. See the native libraries documentation for a list of the settings.

BdfFont and fonts

The NuGet package contains several bitmap fonts (.bdf) that are suitable for writing on the display.

These are:

  • 4x6
  • 5x7, 5x8
  • 6x9, 6x10, 6x12, 6x13, 6x13B, 6x13O, clR6x12
  • 7x13, 7x13B, 7x13O, 7x14, 7x14B
  • 8x13, 8x13B, 8x13O
  • 9x15, 9x15B, 9x18, 9x18B
  • helvR12
  • texgyre-27
  • tom-thumb

When building your project the NuGet package will copy all these fonts as a .bdf file into the output directory of your application. The library will look here as a standard location.

Loading and using a font is easy:

var font = new BdfFont("6x13.bdf");

// Write a red "Thank you!" starting at position 1, 20
canvas.DrawText(font, 1, 20, new Color(0, 255, 0), "Thank you!");

Of course you can also use other bdf fonts. I found a collection of different bdf fonts (under various licenses) here: olikraus/u8g2.

Run your programs (or the samples) as root

The rpi-rgb-led-matrix library needs to initialize some low-level hardware that is required for pulse control / timings and it needs to set the rendering thread priority to high to be fast enough to not produce flicker. These initializations require root permissions. After initializiation, it is typically not desirable to stay in this role, so the library then drops the privileges.

Further information can be found in the original docs.

See also the Examples documentation.

Building this library and examples

After cloning this repo, please make sure to initialize the submodule with the native library:
git submodule update --init --recursive.

Since cross-compiling the native library is difficult, especially for a non-C++ dev like me 😉, this library is meant to be compiled on a Raspberry Pi.

Installing the prerequisites

We need:

  1. A C++ compiler toolchain and make.
    Raspbian Buster (full) had everything for this pre-installed.
  2. The .NET Core SDK 3.1
  3. Powershell Core

The shell-script install-prereqs.sh will download the .NET Core SDK, the ASP.NET Core Runtime and Powershell Core and install it in your user's home folder. It will also put dotnet and pwsh on your path in your .profile file. Make sure you source that file or create a new login shell for the path changes to apply.

Building

Run pwsh ./build.ps1 from the root of this project. This will build the native library, build the SharpPiLed library and create a NuGet package in the ./nugets folder and then build all example projects in the src/examples folder.