RaspberryIO_26/Unosquare.WiringPi/Native/WiringPi.Spi.cs

using System;
using System.Runtime.InteropServices;

namespace Unosquare.WiringPi.Native {
  public partial class WiringPi {
    #region WiringPi - SPI Library Calls

    /// <summary>
    /// This function is undocumented.
    /// </summary>
    /// <param name="channel">The channel.</param>
    /// <returns>Unknown.</returns>
    [DllImport(WiringPiLibrary, EntryPoint = "wiringPiSPIGetFd", SetLastError = true)]
    public static extern Int32 WiringPiSPIGetFd(Int32 channel);

    /// <summary>
    /// This performs a simultaneous write/read transaction over the selected SPI bus. Data that was in your buffer is overwritten by data returned from the SPI bus.
    /// That’s all there is in the helper library. It is possible to do simple read and writes over the SPI bus using the standard read() and write() system calls though –
    /// write() may be better to use for sending data to chains of shift registers, or those LED strings where you send RGB triplets of data.
    /// Devices such as A/D and D/A converters usually need to perform a concurrent write/read transaction to work.
    /// </summary>
    /// <param name="channel">The channel.</param>
    /// <param name="data">The data.</param>
    /// <param name="len">The length.</param>
    /// <returns>The result.</returns>
    [DllImport(WiringPiLibrary, EntryPoint = "wiringPiSPIDataRW", SetLastError = true)]
    public static extern Int32 WiringPiSPIDataRW(Int32 channel, Byte[] data, Int32 len);

    /// <summary>
    /// This function is undocumented.
    /// </summary>
    /// <param name="channel">The channel.</param>
    /// <param name="speed">The speed.</param>
    /// <param name="mode">The mode.</param>
    /// <returns>Unkown.</returns>
    [DllImport(WiringPiLibrary, EntryPoint = "wiringPiSPISetupMode", SetLastError = true)]
    public static extern Int32 WiringPiSPISetupMode(Int32 channel, Int32 speed, Int32 mode);

    /// <summary>
    /// This is the way to initialize a channel (The Pi has 2 channels; 0 and 1). The speed parameter is an integer
    /// in the range 500,000 through 32,000,000 and represents the SPI clock speed in Hz.
    /// The returned value is the Linux file-descriptor for the device, or -1 on error. If an error has happened, you may use the standard errno global variable to see why.
    /// </summary>
    /// <param name="channel">The channel.</param>
    /// <param name="speed">The speed.</param>
    /// <returns>The Linux file descriptor for the device or -1 for error.</returns>
    [DllImport(WiringPiLibrary, EntryPoint = "wiringPiSPISetup", SetLastError = true)]
    public static extern Int32 WiringPiSPISetup(Int32 channel, Int32 speed);

    #endregion
  }
}