Support for multiple PiFace

.vs/ProjectSettings.json

@@ -0,0 +1,3 @@
+{
+  "CurrentProjectSetting": null
+}

.vs/VSWorkspaceState.json

@@ -0,0 +1,8 @@
+{
+  "ExpandedNodes": [
+    "",
+    "\\src"
+  ],
+  "SelectedNode": "\\src\\Kingsland.PiFaceSharp.sln",
+  "PreviewInSolutionExplorer": false
+}

src/Kingsland.PiFaceSharp/Spi/HardwareSpiDevice.cs

@@ -14,17 +14,36 @@ public sealed class HardwareSpiDevice : ISpiDevice, IDisposable
         private const int TxRxBufferLength = 3;
         private IntPtr _txBufferPtr = IntPtr.Zero;
         private IntPtr _rxBufferPtr = IntPtr.Zero;
+        private byte SPI_SLAVE_ID = 0x40;
+        private const byte SPI_SLAVE_ADDR = 0;
+        private const byte SPI_SLAVE_MSG_END = 0x0E;
+        private const byte SPI_SLAVE_READ = 1;
+        private const byte SPI_SLAVE_WRITE = 0;
 
         #endregion
 
         #region Constructors
-
-        public HardwareSpiDevice(uint bus, uint chipSelect, string deviceName)
+        /// <summary>
+        /// 
+        /// </summary>
+        /// <param name="bus"></param>
+        /// <param name="chipSelect"></param>
+        /// <param name="deviceName"></param>
+        /// <param name="slaveId">
+        /// PiFace addresses:
+        /// <para>1st => 0x40</para>
+        /// <para>2nd => 0x42</para>
+        /// <para>3rd => 0x44</para>
+        /// <para>4th => 0x46</para>
+        /// <para>NOTE: Address must be "selected" on PiFace with the address jumpers</para>
+        ///</param>
+        public HardwareSpiDevice(uint bus, uint chipSelect, string deviceName, byte slaveId = 0x40)
         {
             this.Bus = bus;
             this.ChipSelect = chipSelect;
             this.SpiDelay = 0;
             this.DeviceName = deviceName;
+            this.SPI_SLAVE_ID = slaveId;
         }
 
         ~HardwareSpiDevice()
@@ -86,7 +105,6 @@ private ushort SpiDelay
         #endregion
 
         #region Methods
-
         private void InitTxRxBuffers()
         {
             // create unmanaged transmit and receive buffers
@@ -111,9 +129,6 @@ private void FreeTxRxBuffers()
 
         #region ISpiDevice Interface
 
-        private const byte CMD_WRITE = 0x40;
-        private const byte CMD_READ = 0x41;
-
         public void Open(int flags)
         {
             if (this.DeviceHandle != 0)
@@ -151,8 +166,10 @@ public void Close()
         /// <returns></returns>
         public byte ReadByte(byte address)
         {
+            byte buffer = SPI_SLAVE_ID;
+            buffer |= (SPI_SLAVE_ADDR << 1 & SPI_SLAVE_MSG_END) | SPI_SLAVE_READ;
             //Console.WriteLine("    spiBufTx = {0} {1} {2}", CMD_READ, address, 0);
-            Marshal.Copy(new byte[] { CMD_READ, address, 0 }, 0, this._txBufferPtr, HardwareSpiDevice.TxRxBufferLength);
+            Marshal.Copy(new byte[] { buffer, address, 0 }, 0, this._txBufferPtr, HardwareSpiDevice.TxRxBufferLength);
             Marshal.Copy(new byte[] { 0, 0, 0 }, 0, this._rxBufferPtr, HardwareSpiDevice.TxRxBufferLength);
             // build the command
             var cmd = SpiDev.SPI_IOC_MESSAGE(1);
@@ -183,12 +200,14 @@ public byte ReadByte(byte address)
 
         /// <summary>
         /// Write a value to the SPI bus.
-        /// </summary>
+        /// </summary><
         /// <param name="address"></param>
         /// <param name="value"></param>
         public void WriteByte(byte address, byte value)
         {
-            Marshal.Copy(new byte[] { CMD_WRITE, address, value }, 0, this._txBufferPtr, HardwareSpiDevice.TxRxBufferLength);
+            byte buffer = SPI_SLAVE_ID;
+            buffer |= (SPI_SLAVE_ADDR << 1 & SPI_SLAVE_MSG_END) | SPI_SLAVE_WRITE;
+            Marshal.Copy(new byte[] { buffer, address, value }, 0, this._txBufferPtr, HardwareSpiDevice.TxRxBufferLength);
             Marshal.Copy(new byte[] { 0, 0, 0 }, 0, this._rxBufferPtr, HardwareSpiDevice.TxRxBufferLength);
             // build the command
             var cmd = SpiDev.SPI_IOC_MESSAGE(1);