Remove ChipSelect default value in SpiConectionSettings (#59)

Author: Ellerbach

System.Device.Spi/SpiConnectionSettings.cs

@@ -38,8 +38,9 @@ private SpiConnectionSettings()
         /// Initializes a new instance of the <see cref="SpiConnectionSettings"/> class.
         /// </summary>
         /// <param name="busId">The bus ID the device is connected to.</param>
-        /// <param name="chipSelectLine">The chip select line used on the bus. Optional, -1 if not used</param>
-        public SpiConnectionSettings(int busId, int chipSelectLine = -1)
+        /// <param name="chipSelectLine">The chip select line used on the bus. In .NET nanoFramework, you need to have a
+        /// valid GPIO Chip Select even if you don't use it.</param>
+        public SpiConnectionSettings(int busId, int chipSelectLine)
         {
             BusId = busId;
             ChipSelectLine = chipSelectLine;

Test/SpiHardwareUnitTests/SimpleSpiTests.cs

@@ -36,8 +36,7 @@ public void TryToSeeIfSpiIsSupported()
         public void CheckSpiConectionSettings()
         {
             // Arrange
-            SpiConnectionSettings connectinSettings = new SpiConnectionSettings(1);
-            connectinSettings.ChipSelectLine = 12;
+            SpiConnectionSettings connectinSettings = new SpiConnectionSettings(1, 12);
             connectinSettings.ChipSelectLineActiveState = PinValue.High;
             connectinSettings.ClockFrequency = 1_000_000;
             connectinSettings.DataBitLength = 8;