Class RotaryEncoderWithButton | Meadow.Foundation API website

Remarks

RotaryEncoderWithButton
Status
Source code	GitHub
NuGet package

Rotary encoders are similar in form factor to potentiometers, but instead of modifying a voltage output, they send a digital signal encoded using Gray Code when rotated that can be decoded to ascertain the direction of turn.

Rotary encoders have several advantages over potentiometers as input devices, namely:

They’re more power efficient; they only use power when actuated.
They’re not rotation-bound; they spin infinitely in either direction.
Many rotary encoders also have a built-in pushbutton.

Rotary encoders are used almost exclusively on things like volume knobs on stereos.

And because they’re not rotation bound, they are especially useful in the case in which a device might have multiple inputs to control the same parameter. For instance, a stereo’s volume might be controlled via a knob and a remote control. If a potentiometer were used for the volume knob, then the actual volume could get out of synch with the apparent value on the potentiometer when the volume was changed via the remote.

For this reason, rotary encoders are particularly useful in connected things, in which parameters might be controlled remotely.

Code Example

protected int value = 0;
protected RotaryEncoderWithButton rotaryEncoder;

public override Task Initialize()
{
    Console.WriteLine("Initializing Hardware...");

    // Note: on the rotary encoder in the hack kit, the pinout is as
    // follows:
    //
    // | Encoder Name | Driver Pin Name |
    // |--------------|-----------------|
    // | `SW`         | `buttonPin`     |
    // | `DT`         | `aPhasePin`     |
    // | `CLK`        | `bPhasePin`     |

    // initialize the encoder
    rotaryEncoder = new RotaryEncoderWithButton(Device, Device.Pins.D07, Device.Pins.D08, Device.Pins.D06);

    //==== Classic Events
    rotaryEncoder.Rotated += RotaryEncoder_Rotated;

    //==== IObservable
    var observer = RotaryEncoder.CreateObserver(
        handler: result => { Console.WriteLine("Observer triggered, rotation has switched!"); },
        // only notify if the rotation has switched (a little contrived, but a fun use of filtering)
        filter: result => result.Old != null && result.New != result.Old.Value
        // for all events, pass null or return true for filter:
        //filter: null
    );
    rotaryEncoder.Subscribe(observer);

    rotaryEncoder.Clicked += (s, e) => Console.WriteLine("Button Clicked");

    rotaryEncoder.PressEnded += (s, e) => Console.WriteLine("Press ended");

    rotaryEncoder.PressStarted += (s, e) => Console.WriteLine("Press started");

    Console.WriteLine("Hardware initialization complete.");

    return Task.CompletedTask;
}

private void RotaryEncoder_Rotated(object sender, RotaryChangeResult e)
{
    switch (e.New) 
    {
        case RotationDirection.Clockwise:
            value++;
            Console.WriteLine("/\\ Value = {0} CW", value);
            break;
        case RotationDirection.CounterClockwise:
            value--;
            Console.WriteLine("\\/ Value = {0} CCW", value);
            break;
    }
}

Sample project(s) available on GitHub

Two-bit Gray Code

This rotary encoder driver works with most rotary encoders which return a two-bit Gray Code which is the minimum number of bits necessary to describe direction. Most common rotary encoders use two-bit Gray Code, so this driver should work with most common rotary encoders.

PushButton

Some rotary encoders, such as the ones pictured above, have an integrated push button. This driver exposes that button as a PushButton via the Button property.

The following example shows how to register event handlers to print in the console when pressing and relasing the push button:

public class MeadowApp : App<F7Micro, MeadowApp>
{
    protected RotaryEncoderWithButton _rotary = null;
    protected PwmLed _led = null;
    // how much to change the brightness per rotation step. 
    // 0.05 = 20 clicks to 100%
    protected float _brightnessStepChange = 0.05F; 

    public MeadowApp()
    {
        // instantiate our peripherals
        _rotary = new RotaryEncoderWithButton(Device, Device.Pins.D07, Device.Pins.D08, Device.Pins.D06);
        _rotary.Rotated += RotaryRotated;
        _rotary.Clicked += RotaryClicked;

        _led = new PwmLed(Device.Pins.D12, TypicalForwardVoltage.Red);
    }

    protected void RotaryRotated(object sender, RotaryTurnedEventArgs e)
    {
        // if clockwise, turn it up! clamp to 1, so we don't go over.
        if (e.Direction == RotationDirection.Clockwise)
        {
            if(_led.Brightness >= 1) 
            {
                return;
            } 
            else 
            {
                _led.SetBrightness((_led.Brightness + 
                    _brightnessStepChange).Clamp(0,1));
            }
        } 
        else // otherwise, turn it down. clamp to 0 so we don't go below. 
        { 
            if (_led.Brightness <= 0) 
            {
                return;
            } 
            else 
            {
                _led.SetBrightness((_led.Brightness - 
                    _brightnessStepChange).Clamp(0,1));
            }
        }
    }

    private void RotaryClicked(object sender, EventArgs e)
    {
        if (_led.Brightness > 0) 
        {
            _led.SetBrightness(0f);
        } 
        else 
        {
            _led.SetBrightness(_lastOnBrightness);
        }
    }
}

Sample projects available on GitHub

Wiring Example

<img src="../../API_Assets/Meadow.Foundation.Sensors.Rotary.RotaryEncoderWithButton/RotaryEncoderWithButton_Fritzing.svg"

Characteristic	Locus
Inheritance	System.Object ObservableBase<RotationDirection> RotaryEncoder > RotaryEncoderWithButton
Implements	IRotaryEncoder IRotaryEncoderWithButton
Inherited Members	RotaryEncoder.Rotated RotaryEncoder.APhasePort RotaryEncoder.BPhasePort RotaryEncoder.LastDirectionOfRotation ObservableBase<RotationDirection>.observers ObservableBase<RotationDirection>.NotifyObservers(IChangeResult<RotationDirection>) ObservableBase<RotationDirection>.Subscribe(IObserver<IChangeResult<RotationDirection>>) ObservableBase<RotationDirection>.CreateObserver(Action<IChangeResult<RotationDirection>>, Nullable<Predicate<IChangeResult<RotationDirection>>>)
Namespace	Meadow.Foundation.Sensors.Rotary
Assembly	Meadow.Foundation.dll

Syntax

public class RotaryEncoderWithButton : RotaryEncoder, IRotaryEncoder, IRotaryEncoderWithButton

Constructors

RotaryEncoderWithButton(IDigitalInputController, IPin, IPin, IPin, ResistorMode)

Instantiates a new RotaryEncoder on the specified pins that has an integrated button.

Declaration

public RotaryEncoderWithButton(IDigitalInputController device, IPin aPhasePin, IPin bPhasePin, IPin buttonPin, ResistorMode buttonResistorMode = null)

Parameters

Type	Name	Description
IDigitalInputController	device
IPin	aPhasePin
IPin	bPhasePin
IPin	buttonPin
ResistorMode	buttonResistorMode

Properties

Button

Returns the PushButton that represents the integrated button.

Declaration

public PushButton Button { get; }

Property Value

Type	Description
PushButton

LongClickedThreshold

The minimum duration for a long press.

Declaration

public TimeSpan LongClickedThreshold { get; set; }

Property Value

Type	Description
TimeSpan

State

Returns the push button's state

Declaration

public bool State { get; }

Property Value

Type	Description
System.Boolean

Methods

ButtonClicked(Object, EventArgs)

Method when button is clicked (down then up)

Declaration

protected void ButtonClicked(object sender, EventArgs e)

Parameters

Type	Name	Description
System.Object	sender	sender object
EventArgs	e	event arguments

ButtonPressEnded(Object, EventArgs)

Method called when button press is started (up state)

Declaration

protected void ButtonPressEnded(object sender, EventArgs e)

Parameters

Type	Name	Description
System.Object	sender	sender object
EventArgs	e	event arguments

ButtonPressStarted(Object, EventArgs)

Method called when button press is started (down state)

Declaration

protected void ButtonPressStarted(object sender, EventArgs e)

Parameters

Type	Name	Description
System.Object	sender	sender object
EventArgs	e	event arguments

Events

Clicked

Raised when the button circuit is re-opened after it has been closed (at the end of a �press�.

Declaration

public event EventHandler Clicked

Event Type

Type	Description
EventHandler

LongClicked

Raised when the button circuit is pressed for LongPressDuration.

Declaration

public event EventHandler LongClicked

Event Type

Type	Description
EventHandler

PressEnded

Raised when a press ends (the button is released; circuit is opened).

Declaration

public event EventHandler PressEnded

Event Type

Type	Description
EventHandler

PressStarted

Raised when a press starts (the button is pushed down; circuit is closed).

Declaration

public event EventHandler PressStarted

Event Type

Type	Description
EventHandler