Iot: Add instructions on how to samples inside a docker container

[JPThorne]

Updated : This issue is meant to track the addition of the right documentation on how to run a sample app when in the docker container since the lack of that documentation was the reason why the original issue was logged.

---

Description

I get the following error when attempting to use System.Device.Gpio and GpioController on a Raspberry Pi 3 and on a Raspberry Pi 4:

Let's blink an LED!

Unhandled Exception: System.IO.IOException: Error 2 initializing the Gpio driver.
   at System.Device.Gpio.Drivers.RaspberryPi3Driver.Initialize()
   at System.Device.Gpio.Drivers.RaspberryPi3Driver.OpenPin(Int32 pinNumber)
   at System.Device.Gpio.GpioController.OpenPin(Int32 pinNumber)
   at Athy.Device.Simulation.Program.Main(String[] args) in /app/src/Athy.Device.Simulation/Program.cs:line 18

Steps to reproduce

When running this Program.cs via the below Dockerfile:

using System;
using System.Device.Gpio;
using System.Threading;

namespace Athy.Device.Simulation
{
    class Program
    {
        static void Main(string[] args)
        {
            var pin = 17;
            var lightTimeInMilliseconds = 1000;
            var dimTimeInMilliseconds = 200;

            Console.WriteLine($"Let's blink an LED!");
            using (GpioController controller = new GpioController())
            {
                controller.OpenPin(pin, PinMode.Output);
                Console.WriteLine($"GPIO pin enabled for use: {pin}");

                Console.CancelKeyPress += (object sender, ConsoleCancelEventArgs eventArgs) =>
                {
                    controller.Dispose();
                };

                while (true)
                {
                    Console.WriteLine($"Light for {lightTimeInMilliseconds}ms");
                    controller.Write(pin, PinValue.High);
                    Thread.Sleep(lightTimeInMilliseconds);
                    Console.WriteLine($"Dim for {dimTimeInMilliseconds}ms");
                    controller.Write(pin, PinValue.Low);
                    Thread.Sleep(dimTimeInMilliseconds);
                }
            }
        }
    }
}

Dockerfile:

FROM mcr.microsoft.com/dotnet/core/sdk AS build

RUN dotnet --info

RUN mkdir /app
COPY . /app

WORKDIR /app
RUN dotnet restore ./Athy.Collection.Device.sln
RUN dotnet build -c Release ./Athy.Collection.Device.sln -o /build

FROM build AS publish
RUN mkdir /publish
RUN dotnet publish -c Release -o /publish ./src/Athy.Device.Simulation/Athy.Device.Simulation.csproj

# FROM mcr.microsoft.com/dotnet/core/runtime:3.0.0-preview8-buster-slim-arm64v8 as runtime
# FROM microsoft/dotnet:2.1-runtime-stretch-slim-arm32v7
FROM mcr.microsoft.com/dotnet/core/runtime:2.2.6-stretch-slim-arm32v7 as runtime
WORKDIR /app
COPY --from=publish /publish /app

ENTRYPOINT ["dotnet", "Athy.Device.Simulation.dll"]

Expected behavior

I expect no error to happen and the LED on the connected breadboard to blink.

Actual behavior

The error described above happened instead.

Versions used

The following versions are used:

    Iot.Device.Bindings" Version="1.0.0-prerelease.19413.1"
    System.Device.Gpio" Version="1.0.0-prerelease.19413.1"

Extra info

• dotnet --info output:

.NET Core SDK (reflecting any global.json):
 Version:   3.0.100
 Commit:    04339c3a26

Runtime Environment:
 OS Name:     debian
 OS Version:  10
 OS Platform: Linux
 RID:         debian.10-arm
 Base Path:   /usr/share/dotnet/sdk/3.0.100/

Host (useful for support):
  Version: 3.0.0
  Commit:  7d57652f33

.NET Core SDKs installed:
  3.0.100 [/usr/share/dotnet/sdk]

.NET Core runtimes installed:
  Microsoft.AspNetCore.App 3.0.0 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 3.0.0 [/usr/share/dotnet/shared/Microsoft.NETCore.App]

To install additional .NET Core runtimes or SDKs:
  https://aka.ms/dotnet-download

Steps already tried
I have tried various permutations on the following:

• A raspberry pi 3.
• A raspberry pi 4.
• Linux Raspbian.
• Linux Debian with Buster.
• Variations on the GpioController ctor and args.
• The breadboard attached / not attached.

[ZhangGaoxing]

You need to use the --device parameter to mount GPIO devices

[JPThorne]

Hey @ZhangGaoxing thanks for the feedback, that sounds promising. Where would I use that parameter though? In the Dockerfile? Is there some documentation somewhere on how to use that? Thanks!

[ZhangGaoxing]

try this

docker run --device /dev/gpiomem

[JPThorne]

Great that worked! Thanks very much. I guess this can be closed then. Should this be documented somewhere? I couldn't see anything in the samples area: https://github.com/dotnet/iot/blob/master/samples/led-blink/README.md indicating I needed to run it with that --device flag.

[ZhangGaoxing]

@joperezr @krwq 👆

[joperezr]

Yes it should be documented, thanks a lot @ZhangGaoxing for answering the question. We will add these note to our docs for running on a docker container.