Add drivemode for alternate function

source/GpioPinDriveMode.cs

@@ -41,6 +41,10 @@ public enum GpioPinDriveMode
  /// <summary>
  /// Configures the GPIO pin in open collector mode with resistive pull-down mode.
  /// </summary>
- OutputOpenSourcePullDown
+ OutputOpenSourcePullDown,
+ /// <summary>
+ /// Configures the GPIO pin for an alternate function
+ /// </summary>
+ Alternate
  }
 }

source/Gpio​Pin.cs

@@ -27,6 +27,7 @@ public sealed class Gpio​Pin : IDisposable
  private object _syncLock = new object();
 
  private readonly int _pinNumber;
+ private int _alternateFunction = 0;
  private GpioPinDriveMode _driveMode = GpioPinDriveMode.Input;
  private TimeSpan _debounceTimeout = TimeSpan.Zero;
  private GpioPinValueChangedEventHandler _callbacks = null;
@@ -148,26 +149,28 @@ public bool IsDriveModeSupported(GpioPinDriveMode driveMode)
  /// </summary>
  /// <param name="value">An enumeration value that specifies drive mode to use for the GPIO pin.
  /// The drive mode specifies whether the pin is configured as an input or an output, and determines how values are driven onto the pin.</param>
+ /// <param name="alternateFunction">An integer value that specifies the alternate function assigned to the GPIO pin.</param>
  /// <remarks>The following exceptions can be thrown by this method:
  /// <list type="bullet">
  /// <item><term>E_INVALIDARG : The GPIO pin does not support the specified drive mode.</term></item>
  /// <item><term>E_ACCESSDENIED : The pin is open in shared read-only mode.Close the pin and reopen it in exclusive mode to change the drive mode of the pin.</term></item>
  /// </list>
  /// </remarks>
- public void SetDriveMode(GpioPinDriveMode value)
+ public void SetDriveMode(GpioPinDriveMode value, int alternateFunction = 0)
  {
  lock (_syncLock)
  {
  // check if pin has been disposed
  if (_disposedValue) { throw new ObjectDisposedException(); }
 
- if (_driveMode == value) return;
+ if (_driveMode == value && alternateFunction == _alternateFunction) return;
 
  // check if the request drive mode is supported
  // need to call the native method directly because we are already inside a lock
  if (NativeIsDriveModeSupported(value))
  {
- NativeSetDriveMode(value);
+ NativeSetDriveMode(value, alternateFunction);
+ _alternateFunction = alternateFunction;
  _driveMode = value;
  }
  }
@@ -246,7 +249,7 @@ public event GpioPinValueChangedEventHandler ValueChanged
  try
  {
  _callbacks = callbacksNew;
- NativeSetDriveMode(_driveMode);
+ NativeSetDriveMode(_driveMode, _alternateFunction);
  }
  catch
  {
@@ -271,7 +274,7 @@ public event GpioPinValueChangedEventHandler ValueChanged
  try
  {
  _callbacks = callbacksNew;
- NativeSetDriveMode(_driveMode);
+ NativeSetDriveMode(_driveMode, _alternateFunction);
  }
  catch
  {
@@ -351,7 +354,7 @@ public void Dispose()
  private extern bool NativeIsDriveModeSupported(GpioPinDriveMode driveMode);
 
  [MethodImpl(MethodImplOptions.InternalCall)]
- private extern void NativeSetDriveMode(GpioPinDriveMode driveMode);
+ private extern void NativeSetDriveMode(GpioPinDriveMode driveMode, int alternateFunction);
 
  [MethodImpl(MethodImplOptions.InternalCall)]
  private extern bool NativeInit(int pinNumber);