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KeyboardGpioDriver.cs
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KeyboardGpioDriver.cs
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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System;
using System.Collections.Generic;
using System.Device.Gpio;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading;
namespace Iot.Device.Board
{
/// <summary>
/// A GPIO Driver for testing on Windows
/// This driver uses the keyboard for simulating GPIO pins.
/// Pins 0-2 are output only and represent the keyboard LEDs (Caps lock, Scroll Lock and Num Lock).
/// Setting a value to any of these pins toggles the LEDs on the keyboard (if they're physically present).
/// Pins above 8 are input only and represent the keyboard keys. To get the pin number,
/// cast the corresponding <see cref="ConsoleKey"/> to int, e.g. int pinNumber = (int)ConsoleKey.A
/// </summary>
public class KeyboardGpioDriver : GpioDriver
{
private enum LedKey
{
NumLock,
CapsLock,
ScrollLock,
}
private const int SupportedPinCount = 256;
private readonly Dictionary<int, PinValue> _pinValues = new Dictionary<int, PinValue>();
private KeyState[] _state;
private Thread? _pollThread;
private bool _terminateThread;
/// <summary>
/// Creates an instance of the KeyboardGpioDriver
/// </summary>
public KeyboardGpioDriver()
{
_state = new KeyState[SupportedPinCount];
for (int i = 0; i < SupportedPinCount; i++)
{
_state[i] = new KeyState((ConsoleKey)i, i);
}
_pollThread = null;
_terminateThread = true;
foreach (var key in Enum.GetValues(typeof(LedKey)))
{
_pinValues.Add((int)key!, GetLedState((LedKey)key).KeyValue);
}
}
/// <inheritdoc />
protected override int PinCount
{
get
{
// The ConsoleKey enum is used to index into our pins, if needed. This one does not use values below 8, so
// we'll use 3 for the LEDs.
return SupportedPinCount;
}
}
/// <inheritdoc />
protected override int ConvertPinNumberToLogicalNumberingScheme(int pinNumber)
{
return pinNumber;
}
/// <inheritdoc />
protected override void OpenPin(int pinNumber)
{
}
/// <inheritdoc />
protected override void ClosePin(int pinNumber)
{
}
/// <inheritdoc />
protected override void SetPinMode(int pinNumber, PinMode mode)
{
if (IsPinModeSupported(pinNumber, mode))
{
_state[pinNumber].Mode = mode;
}
else
{
throw new NotSupportedException($"Pin {pinNumber} does not support mode {mode}");
}
}
/// <inheritdoc />
protected override PinMode GetPinMode(int pinNumber)
{
return _state[pinNumber].Mode;
}
/// <inheritdoc />
protected override bool IsPinModeSupported(int pinNumber, PinMode mode)
{
if (pinNumber < 3)
{
// Output-only pins (the three LEDs on the keyboard)
if (mode == PinMode.Output)
{
return true;
}
return false;
}
if (pinNumber >= 8)
{
if (mode == PinMode.Input || mode == PinMode.InputPullDown || mode == PinMode.InputPullUp)
{
return true;
}
}
return false;
}
private bool IsKeyPressed(ConsoleKey key)
{
short state = Interop.GetKeyState((int)key);
return (state & 0xFFFE) != 0; // any bits except the lowest
}
private void SetLedState(LedKey key, PinValue state)
{
(int virtualKey, int currentKeyState) = GetLedState(key);
_pinValues[(int)key] = state;
if ((state == PinValue.High && currentKeyState == 0) ||
(state == PinValue.Low && currentKeyState != 0))
{
// Simulate a key press
Interop.keybd_event((byte)virtualKey,
0x45,
Interop.KEYEVENTF_EXTENDEDKEY,
IntPtr.Zero);
// Simulate a key release
Interop.keybd_event((byte)virtualKey,
0x45,
Interop.KEYEVENTF_EXTENDEDKEY | Interop.KEYEVENTF_KEYUP,
IntPtr.Zero);
}
}
private (int VirtualKey, int KeyValue) GetLedState(LedKey key)
{
int virtualKey = 0;
if (key == LedKey.NumLock)
{
virtualKey = Interop.VK_NUMLOCK;
}
else if (key == LedKey.CapsLock)
{
virtualKey = Interop.VK_CAPITAL;
}
else if (key == LedKey.ScrollLock)
{
virtualKey = Interop.VK_SCROLL;
}
else
{
throw new NotSupportedException("No such key");
}
// Bit 1 indicates whether the LED is currently on or off (or, whether Scroll lock, num lock, caps lock is on)
return (virtualKey, Interop.GetKeyState(virtualKey) & 1);
}
/// <inheritdoc />
protected override PinValue Read(int pinNumber)
{
short currentKeyState = Interop.GetAsyncKeyState(pinNumber);
if ((currentKeyState & 0xFFFE) != 0)
{
return PinValue.High;
}
else
{
return PinValue.Low;
}
}
/// <inheritdoc />
protected override void Toggle(int pinNumber) => Write(pinNumber, !_pinValues[pinNumber]);
/// <inheritdoc />
protected override void Write(int pinNumber, PinValue value)
{
if (pinNumber == 0)
{
SetLedState(LedKey.NumLock, value);
}
if (pinNumber == 1)
{
SetLedState(LedKey.ScrollLock, value);
}
if (pinNumber == 2)
{
SetLedState(LedKey.CapsLock, value);
}
}
/// <inheritdoc />
protected override WaitForEventResult WaitForEvent(int pinNumber, PinEventTypes eventTypes, CancellationToken cancellationToken)
{
PinValue oldState = Read(pinNumber);
while (!cancellationToken.IsCancellationRequested)
{
PinValue newState = Read(pinNumber);
if (oldState != newState)
{
if (eventTypes == PinEventTypes.Rising && newState == PinValue.High)
{
return new WaitForEventResult()
{
EventTypes = PinEventTypes.Rising,
TimedOut = false
};
}
else if (eventTypes == PinEventTypes.Falling && newState == PinValue.Low)
{
return new WaitForEventResult()
{
EventTypes = PinEventTypes.Falling,
TimedOut = false
};
}
else
{
return new WaitForEventResult()
{
EventTypes = newState == PinValue.High ? PinEventTypes.Rising : PinEventTypes.Falling,
TimedOut = false
};
}
}
}
return new WaitForEventResult()
{
TimedOut = true
};
}
/// <inheritdoc />
protected override void AddCallbackForPinValueChangedEvent(int pinNumber, PinEventTypes eventTypes, PinChangeEventHandler callback)
{
lock (_state)
{
if (_pollThread == null)
{
_terminateThread = false;
_pollThread = new Thread(PollingKeyThread);
_pollThread.IsBackground = true;
_pollThread.Start();
}
_state[pinNumber].State = Read(pinNumber);
_state[pinNumber].EventModes = _state[pinNumber].EventModes | eventTypes;
_state[pinNumber].Callback += callback;
}
}
/// <inheritdoc />
protected override void RemoveCallbackForPinValueChangedEvent(int pinNumber, PinChangeEventHandler callback)
{
bool terminate;
lock (_state)
{
_state[pinNumber].Callback -= callback;
if (_state[pinNumber].CallbacksExist == false)
{
_state[pinNumber].EventModes = PinEventTypes.None;
}
terminate = _state.All(x => x.CallbacksExist == false);
}
// Can't do this within the lock - would risk a deadlock
if (terminate && _pollThread != null)
{
_terminateThread = true;
_pollThread.Join();
_pollThread = null;
}
}
/// <summary>
/// Poor man's interrupt handling. This class is not for real production use, so doesn't really matter
/// </summary>
private void PollingKeyThread()
{
while (!_terminateThread)
{
lock (_state)
{
foreach (var s in _state)
{
if (s.EventModes != PinEventTypes.None)
{
var newState = Read(s.PinNumber);
if (s.State != newState)
{
s.State = newState;
// Fire either way - the client has to handle that anyway (because other clients may request the other edge)
s.FireCallback(this, new PinValueChangedEventArgs(newState == PinValue.High ? PinEventTypes.Rising : PinEventTypes.Falling, s.PinNumber));
}
}
}
}
Thread.Sleep(10);
}
}
private sealed class KeyState
{
public KeyState(ConsoleKey key, int pinNumber)
{
Key = key;
PinNumber = pinNumber;
State = PinValue.Low;
}
public event PinChangeEventHandler? Callback;
public ConsoleKey Key
{
get;
}
public int PinNumber { get; }
public PinMode Mode
{
get;
set;
}
public PinValue State
{
get;
set;
}
public PinEventTypes EventModes { get; set; }
public bool CallbacksExist
{
get
{
return Callback != null;
}
}
public void FireCallback(object sender, PinValueChangedEventArgs pinValueChangedEventArgs)
{
Callback?.Invoke(sender, pinValueChangedEventArgs);
}
}
}
}