C# .NET 5 Break beam sensor Raspberry PI

Question

I've started a project to counter objects on a production line using a break beam sensor with the Raspberry Pi and Visual Studio Code. I have a python script that works however I need to do it in C#. Currently my code looks like this:

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

Console.WriteLine("Break Beam. Press Ctrl+C to end.");
int pin = 17;
using var controller = new GpioController();
controller.OpenPin(pin, PinMode.Output);
bool BeamBroke = true;
while (true)
{
   controller.Write(pin, ((BeamBroke) ? PinValue.High : PinValue.Low));
   Thread.Sleep(1000);
   BeamBroke = !BeamBroke;
}

The problem is that when I run this console app nothing is written about the beam being broken. There aren't any errors.

Answer 1

You will need to open an input pin with.

controller.OpenPin(pin, PinMode.Input);

You will also need to register a callback to be triggered upon pin value change.

void BeamBreakCallback(object sender, PinValueChangedEventArgs pinValueChangedEventArgs)
{
    BeamBroke = pinValueChangedEventArgs.ChangeType == PinEventTypes.Falling;
}

And then register the callback to be called whenever the input value changes on your input pin.

controller.RegisterCallbackForPinValueChangedEvent(
    pin,
    PinEventTypes.Falling | PinEventTypes.Rising, // trigger on both rising and falling edges
    BeamBreakCallback
);

If you want to write anything to the console you'll need to add something to the callback

void BeamBreakCallback(object sender, PinValueChangedEventArgs pinValueChangedEventArgs)
{
    BeamBroke = pinValueChangedEventArgs.ChangeType == PinEventTypes.Falling;

    if (pinValueChangedEventArgs.ChangeType == PinEventTypes.Falling)
        Console.WriteLine("beam broken");
    else
        Console.WriteLine("beam unbroken");
}

Caveat I've made some assumptions about whether a falling or rising edge represents a broken beam.