C#•2y ago

❔ GPIO listening to button events (Raspbery Pi w breakout board)

Im using GpioController to control the GPIO pins on my Raspberry pi, i have a breakout board with some LEDs on it and a couple of buttons. Controlling the leds has been pretty easy so far, as they are not something I have to actively listen to but I'm trying to make a method that will listen to all connected buttons (there are total of 6 of them) and do something based on when they are pressed (For testing im simply trying to print to console with their respective button number) I've tried a couple of things, but Im having issues in their behavior (you press once, it keeps going off for eternity) and in general I think I'm doing it in a convoluted way. Does anyone know the best method to listen for button presses (on the background) and then upon button press allow them to execute a piece of code? the extent of what I have tried so far mainly revolves around opening all pins that are buttons

public static async Task ButtonWatcher(CancellationToken token)
    {
        while (!token.IsCancellationRequested)
        {
            List<int> buttonList = new List<int>() {22,27,17,4,3,6};
            foreach (int pin in buttonList)
            {
                _controller.OpenPin(pin);
            }
            // Logic here to listen to them
        }
    }

public static async Task ButtonWatcher(CancellationToken token)
    {
        while (!token.IsCancellationRequested)
        {
            List<int> buttonList = new List<int>() {22,27,17,4,3,6};
            foreach (int pin in buttonList)
            {
                _controller.OpenPin(pin);
            }
            // Logic here to listen to them
        }
    }

I have no idea if this is the right approach and any pointers would be greatly appreciated

38 Replies

dvdOP•2y ago

Oh and the _controller is just an instance of gpiocontroller GpioController _controller = new GpioController();

canton7•2y ago

Are you sure you've set the pull-ups/pull-downs on the button inputs as appropriate? Or do you have external pull-up/pull-down resistors?

dvdOP•2y ago

They are setup yeah

canton7•2y ago

Where? Are they external? Your code doesn't enable the internal pull-ups/pull-downs?

dvdOP•2y ago

Its a breakout board that is wired to another one that has resistors on them It functions properly in a python project it came with, not sure how they handle it

canton7•2y ago

I'd also avoid calling OpenPin on every loop iteration Also try specifying the PinMode when you call OpenPin?

dvdOP•2y ago

Good points Is there a more elegant way to open all these pins in 1 go?

canton7•2y ago

Also, what's the logic in // Logic here to listen to them? Maybe that has a problem Doesn't look like it, from the docs Although I'm not familiar with GpioController itself

dvdOP•2y ago

They are are a bunch of tasks that refer to a corresponding method based on the pin number

static async Task PinEvent4(CancellationToken token)
    {
        while (!token.IsCancellationRequested)
        {
            WaitForEventResult waitResult;
            waitResult = await _controller.WaitForEventAsync(4, PinEventTypes.Falling, token);
            int count = 0;
            do
            {
                if (!waitResult.TimedOut)
                {
                    Console.WriteLine(
                        $"[{count++}] Button was pressed: GPIO pin number 4, ChangeType={waitResult.EventTypes}");
                    Thread.Sleep(1000);
                }
            } while (waitResult.EventTypes != PinEventTypes.Rising);

            await Task.Delay(Timeout.Infinite, token);
        }
    }

static async Task PinEvent4(CancellationToken token)
    {
        while (!token.IsCancellationRequested)
        {
            WaitForEventResult waitResult;
            waitResult = await _controller.WaitForEventAsync(4, PinEventTypes.Falling, token);
            int count = 0;
            do
            {
                if (!waitResult.TimedOut)
                {
                    Console.WriteLine(
                        $"[{count++}] Button was pressed: GPIO pin number 4, ChangeType={waitResult.EventTypes}");
                    Thread.Sleep(1000);
                }
            } while (waitResult.EventTypes != PinEventTypes.Rising);

            await Task.Delay(Timeout.Infinite, token);
        }
    }

This is pin 4 for example, mainly trying to get one button working properly before moving on to all

dvdOP•2y ago

Which after pressing the button once results in this

canton7•2y ago

Wait, that means the pin is constantly rising/falling, rather than just being stuck low?

dvdOP•2y ago

It seems so, but only after the initial press If i do rising, it will always be going off Ill give it a quick try though with pinmode as input

canton7•2y ago

Ah, d'oh

            do
            {
                if (!waitResult.TimedOut)
                {
                    Console.WriteLine(
                        $"[{count++}] Button was pressed: GPIO pin number 4, ChangeType={waitResult.EventTypes}");
                    Thread.Sleep(1000);
                }
            } while (waitResult.EventTypes != PinEventTypes.Rising);

            do
            {
                if (!waitResult.TimedOut)
                {
                    Console.WriteLine(
                        $"[{count++}] Button was pressed: GPIO pin number 4, ChangeType={waitResult.EventTypes}");
                    Thread.Sleep(1000);
                }
            } while (waitResult.EventTypes != PinEventTypes.Rising);

There's no code to re-read waitResult in there So yeah, of course it keeps printing the waitResult -- because it's Falling when you enter that loop, and it's never re-assigned so it never becomes something other than Falling

dvdOP•2y ago

ahh

canton7•2y ago

Also don't use Thread.Sleep in async code. If you need to delay, use await Task.Delay(...)

dvdOP•2y ago

Alright, ill give it a quick test, ill reassign waitResult.EvenTypes to rising and ive set the pin type to input Yeah that stopped it from repeating I think i should flip them actually, i only picked falling because it was spamming on rising

canton7•2y ago

What's the point of that loop anyway? Just print all edges?

dvdOP•2y ago

Im not sure what you mean with print all edges

canton7•2y ago

What are you trying to achieve with that loop?

dvdOP•2y ago

But my basic goal is to have a press of 'button 1' result in 'Button 1 was pressed' to show up in console (I mean later there will be logic tied to what it needs to execute but thats not important for now) And only do that once, for every time i press a button

dvdOP•2y ago

It sort of works now i think, it just prints it out 4 times each time i press it assuming I want the 500ms task delay i put in

canton7•2y ago

Ah, so:

    static async Task PinEvent4(CancellationToken token)
    {
        int count = 0;
        while (!token.IsCancellationRequested)
        {
            var waitResult = await _controller.WaitForEventAsync(4, PinEventTypes.Falling, token);
            if (waitResult.EventTypes.HasFlag(PinEventTypes.Falling))
            {
                Console.WriteLine(
                        $"[{count++}] Button was pressed: GPIO pin number 4, ChangeType={waitResult.EventTypes}");
            }
        }
    }

    static async Task PinEvent4(CancellationToken token)
    {
        int count = 0;
        while (!token.IsCancellationRequested)
        {
            var waitResult = await _controller.WaitForEventAsync(4, PinEventTypes.Falling, token);
            if (waitResult.EventTypes.HasFlag(PinEventTypes.Falling))
            {
                Console.WriteLine(
                        $"[{count++}] Button was pressed: GPIO pin number 4, ChangeType={waitResult.EventTypes}");
            }
        }
    }

dvdOP•2y ago

I will say this current code is the result of just throwing shit at the wall and seeing what sticks, i think i overcomplicated it for no reason Yeah

static async Task PinEvent4(CancellationToken token)
    {
        while (!token.IsCancellationRequested)
        {
            WaitForEventResult waitResult;
            waitResult = await _controller.WaitForEventAsync(4, PinEventTypes.Falling, token);
            do
            {
                if (!waitResult.TimedOut)
                {
                    Console.WriteLine(
                        $"[Button 4, ChangeType={waitResult.EventTypes}");
                    await Task.Delay(100);
                    waitResult.EventTypes = PinEventTypes.Rising;
                }
            } while (waitResult.EventTypes != PinEventTypes.Rising);
            await Task.Delay(500, token);
        }
    }

static async Task PinEvent4(CancellationToken token)
    {
        while (!token.IsCancellationRequested)
        {
            WaitForEventResult waitResult;
            waitResult = await _controller.WaitForEventAsync(4, PinEventTypes.Falling, token);
            do
            {
                if (!waitResult.TimedOut)
                {
                    Console.WriteLine(
                        $"[Button 4, ChangeType={waitResult.EventTypes}");
                    await Task.Delay(100);
                    waitResult.EventTypes = PinEventTypes.Rising;
                }
            } while (waitResult.EventTypes != PinEventTypes.Rising);
            await Task.Delay(500, token);
        }
    }

This is what i have now, made it a bit shorter since that Console.WriteLine doesnt need to be very detailed anyway

canton7•2y ago

That do...while and waitResult.EventTypes = PinEventTypes.Rising; just cancel each other out It means you'll never loop around that loop more than once And once you strip that out, it starts looking like my code

dvdOP•2y ago

thats true

canton7•2y ago

Oh, unless it's TimedOut, but that won't happen anyway? And besides you've got the outer loop for that

dvdOP•2y ago

Yeah good point Im gonna try yours now, one slight edit because I just did the order wrong for Rising and Falling; it was spamming falling over and over until i would press and hold the button

canton7•2y ago

Also it's racey: if you get an edge after WaitForEventAsync returns before you call it again, you'll miss that event

dvdOP•2y ago

Yeah, im not sure how to best approach that ideally it wouldnt matter how quickly you spam the button

canton7•2y ago

https://learn.microsoft.com/en-us/dotnet/api/system.device.gpio.gpiocontroller.registercallbackforpinvaluechangedevent?view=iot-dotnet-latest ?

GpioController.RegisterCallbackForPinValueChangedEvent Method (Syst...

Adds a callback that will be invoked when pinNumber has an event of type eventType.

dvdOP•2y ago

Could you give me pointers on how to implement that? I'm not really certain how to do it if not thats fine too, I think this was in one of my open tabs but i couldnt figure it out or find a guide online

canton7•2y ago

Looking at the docs,

_controller.RegisterCallbackForPinValueChangedEvent(4, PinEventTypes.Falling, PinChangedHandler);

void PinChangedHandler(object sender, PinValueChangedEventArgs args)
{
    Console.WriteLine($"Pin {args.PinNumber}: {args.ChangeType}");
}

_controller.RegisterCallbackForPinValueChangedEvent(4, PinEventTypes.Falling, PinChangedHandler);

void PinChangedHandler(object sender, PinValueChangedEventArgs args)
{
    Console.WriteLine($"Pin {args.PinNumber}: {args.ChangeType}");
}

Or whatever PinEventTypes you care about -- PinEventTypes.Rising | PinEventTypes.Falling for both

dvdOP•2y ago

Alright, thanks! Ill give this a try, thanks for all the help Canton

canton7•2y ago

Sweet! No worries

dvdOP•2y ago

Also fun little problem, i noticed if i hover my finger like a half an inch / few mm above the button it is already activating lol

canton7•2y ago

Hah That strongly suggests that you don't have those pull-up resistors working right?

dvdOP•2y ago

Yep, I think something got disconnected

Accord•2y ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

Gaming

Programming

❔ GPIO listening to button events (Raspbery Pi w breakout board)