fixes and improvements

src/Meadow.Modbus/Clients/Extensions.cs

@@ -12,7 +12,6 @@ public static class Extensions
     /// Converts a set of Modbus registers (ushort[]) to integers (int[]) assuming little-endina ordering
     /// </summary>
     /// <param name="registers"></param>
-    /// <returns></returns>
     public static int[] ConvertRegistersToInt32(this ushort[] registers)
     {
         var values = new int[registers.Length / 2];
@@ -28,6 +27,17 @@ public static int[] ConvertRegistersToInt32(this ushort[] registers)
         return values;
     }
 
+    /// <summary>
+    /// Converts ushort registers to a single Int32, starting at a specific offset
+    /// </summary>
+    /// <param name="registers">The registers</param>
+    /// <param name="startOffset">The offset in the registers to begine extraction</param>
+    /// <param name="swappedWords">True to convert from big-endian words</param>
+    public static int ExtractInt32(this ushort[] registers, int startOffset = 0, bool swappedWords = false)
+    {
+        return registers.AsSpan().ExtractInt32(startOffset, swappedWords);
+    }
+
     /// <summary>
     /// Converts ushort registers to a single Int32, starting at a specific offset
     /// </summary>
@@ -140,6 +150,17 @@ public static ulong ExtractUInt64(this Span<ushort> registers, int startOffset =
         }
     }
 
+    /// <summary>
+    /// Converts 4 ushort registers to a IEEE 64 floating point, starting at a specific offset
+    /// </summary>
+    /// <param name="registers">The registers</param>
+    /// <param name="startOffset">The offset in the registers to begine extraction</param>
+    /// <param name="swappedWords">True to convert from big-endian words</param>
+    public static double ExtractDouble(this ushort[] registers, int startOffset = 0, bool swappedWords = false)
+    {
+        return registers.AsSpan().ExtractDouble(startOffset, swappedWords);
+    }
+
     /// <summary>
     /// Converts 4 ushort registers to a IEEE 64 floating point, starting at a specific offset
     /// </summary>
@@ -148,6 +169,8 @@ public static ulong ExtractUInt64(this Span<ushort> registers, int startOffset =
     /// <param name="swappedWords">True to convert from big-endian words</param>
     public static double ExtractDouble(this Span<ushort> registers, int startOffset = 0, bool swappedWords = false)
     {
+        if (registers.Length < 4) throw new ArgumentException("registers does not contain enough data to extract a double");
+
         if (swappedWords)
         {
             byte[] value = BitConverter.GetBytes(registers[startOffset + 0])
@@ -170,6 +193,17 @@ public static double ExtractDouble(this Span<ushort> registers, int startOffset
         }
     }
 
+    /// <summary>
+    /// Converts 2 ushort registers to a IEEE 32 floating point, starting at a specific offset
+    /// </summary>
+    /// <param name="registers">The registers</param>
+    /// <param name="startOffset">The offset in the registers to begine extraction</param>
+    /// <param name="swappedWords">True to convert from big-endian words</param>
+    public static float ExtractSingle(this ushort[] registers, int startOffset = 0, bool swappedWords = false)
+    {
+        return registers.AsSpan().ExtractSingle(startOffset, swappedWords);
+    }
+
     /// <summary>
     /// Converts 2 ushort registers to a IEEE 32 floating point, starting at a specific offset
     /// </summary>

src/Meadow.Modbus/Clients/ModbusRtuClient.cs

@@ -144,13 +144,13 @@ protected override async Task<byte[]> ReadResult(ModbusFunction function)
 
         switch (function)
         {
-            case ModbusFunction.WriteMultipleRegisters:
+            case ModbusFunction.WriteRegister:
             case ModbusFunction.WriteMultipleCoils:
             case ModbusFunction.WriteCoil:
                 bufferLen = 8; //fixed length
                 resultLen = 0; //no result data
                 break;
-            case ModbusFunction.WriteRegister:
+            case ModbusFunction.WriteMultipleRegisters:
                 bufferLen = 7 + header[headerLen - 1];
                 resultLen = header[2];
                 break;

src/Meadow.Modbus/ModbusPolledDevice.cs

@@ -24,6 +24,11 @@ public abstract class ModbusPolledDevice
     /// </summary>
     public event EventHandler<Exception>? CommError;
 
+    /// <summary>
+    /// Raised when data has been read from the device
+    /// </summary>
+    public event EventHandler? DataUpdated;
+
     /// <summary>
     /// Represents the possible formats of source registers
     /// </summary>
@@ -83,7 +88,8 @@ private class RegisterMapping
     /// </summary>
     public virtual void StartPolling()
     {
-        _timer.Change(_refreshPeriosMs, -1);
+        // trigger first read immediately - subsequent reads will be at the desired frequency
+        _timer.Change(0, -1);
     }
 
     /// <summary>
@@ -126,6 +132,17 @@ protected async Task WriteHoldingRegister(ushort startRegister, params ushort[]
         }
     }
 
+    /// <summary>
+    /// Writes one or more values to the holding registers of the Modbus device.
+    /// </summary>
+    /// <param name="startRegister">The starting register address.</param>
+    /// <param name="count">The number of registers to read.</param>
+    /// <returns>A task representing the asynchronous write operation.</returns>
+    protected Task<ushort[]> ReadHoldingRegisters(ushort startRegister, int count)
+    {
+        return _client.ReadHoldingRegisters(_address, startRegister, count);
+    }
+
     /// <summary>
     /// Reads a value from a coil register of the Modbus device.
     /// </summary>
@@ -361,6 +378,8 @@ private async void RefreshTimerProc(object _)
         {
             await MoveHoldingRegistersToProperties();
             await MoveInputRegistersToProperties();
+
+            DataUpdated?.Invoke(this, EventArgs.Empty);
         }
         finally
         {
@@ -517,17 +536,27 @@ private void UpdateField(ushort[] data, RegisterMapping mapping)
             }
             else if (
                 mapping.FieldInfo!.FieldType == typeof(byte) ||
+                mapping.FieldInfo!.FieldType == typeof(ushort) ||
                 mapping.FieldInfo!.FieldType == typeof(short) ||
                 mapping.FieldInfo!.FieldType == typeof(int) ||
+                mapping.FieldInfo!.FieldType == typeof(uint) ||
                 mapping.FieldInfo!.FieldType == typeof(long))
             {
                 UpdateIntegerField(data, mapping);
             }
             else if (
-                mapping.PropertyInfo!.PropertyType == typeof(bool))
+                mapping.FieldInfo!.FieldType == typeof(bool))
             {
                 UpdateBooleanField(data, mapping);
             }
+            else if (
+                mapping.FieldInfo!.FieldType == typeof(ushort[]) ||
+                mapping.FieldInfo!.FieldType == typeof(short[]))
+            {
+                // the field is a ref value, so this is valid
+                ushort[] f = (ushort[])mapping.FieldInfo.GetValue(this);
+                Array.Copy(data, f, Math.Min(data.Length, f.Length));
+            }
             else
             {
                 throw new NotSupportedException();
@@ -670,10 +699,18 @@ private void UpdateIntegerField(ushort[] data, RegisterMapping mapping)
         {
             mapping.FieldInfo!.SetValue(this, Convert.ToInt16(final));
         }
+        else if (mapping.FieldInfo!.FieldType == typeof(ushort))
+        {
+            mapping.FieldInfo!.SetValue(this, Convert.ToUInt16(final));
+        }
         else if (mapping.FieldInfo!.FieldType == typeof(int))
         {
             mapping.FieldInfo!.SetValue(this, Convert.ToInt32(final));
         }
+        else if (mapping.FieldInfo!.FieldType == typeof(uint))
+        {
+            mapping.FieldInfo!.SetValue(this, Convert.ToUInt32(final));
+        }
         else if (mapping.FieldInfo!.FieldType == typeof(long))
         {
             mapping.FieldInfo!.SetValue(this, final);