143 lines
4.6 KiB
C#
143 lines
4.6 KiB
C#
namespace Modbus.IO
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{
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using System;
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using System.Diagnostics;
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using System.IO;
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using System.Linq;
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using Message;
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using Utility;
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/// <summary>
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/// Refined Abstraction - http://en.wikipedia.org/wiki/Bridge_Pattern
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/// </summary>
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internal class ModbusRtuTransport : ModbusSerialTransport
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{
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public const int RequestFrameStartLength = 7;
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public const int ResponseFrameStartLength = 4;
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internal ModbusRtuTransport(IStreamResource streamResource)
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: base(streamResource)
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{
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Debug.Assert(streamResource != null, "Argument streamResource cannot be null.");
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}
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public static int RequestBytesToRead(byte[] frameStart)
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{
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byte functionCode = frameStart[1];
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int numBytes;
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switch (functionCode)
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{
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case Modbus.ReadCoils:
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case Modbus.ReadInputs:
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case Modbus.ReadHoldingRegisters:
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case Modbus.ReadInputRegisters:
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case Modbus.WriteSingleCoil:
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case Modbus.WriteSingleRegister:
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case Modbus.Diagnostics:
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numBytes = 1;
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break;
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case Modbus.WriteMultipleCoils:
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case Modbus.WriteMultipleRegisters:
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byte byteCount = frameStart[6];
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numBytes = byteCount + 2;
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break;
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default:
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string msg = $"Function code {functionCode} not supported.";
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Debug.WriteLine(msg);
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throw new NotImplementedException(msg);
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}
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return numBytes;
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}
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public static int ResponseBytesToRead(byte[] frameStart)
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{
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byte functionCode = frameStart[1];
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// exception response
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if (functionCode > Modbus.ExceptionOffset)
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{
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return 1;
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}
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int numBytes;
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switch (functionCode)
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{
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case Modbus.ReadCoils:
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case Modbus.ReadInputs:
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case Modbus.ReadHoldingRegisters:
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case Modbus.ReadInputRegisters:
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numBytes = frameStart[2] + 1;
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break;
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case Modbus.WriteSingleCoil:
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case Modbus.WriteSingleRegister:
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case Modbus.WriteMultipleCoils:
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case Modbus.WriteMultipleRegisters:
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case Modbus.Diagnostics:
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numBytes = 4;
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break;
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default:
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string msg = $"Function code {functionCode} not supported.";
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Debug.WriteLine(msg);
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throw new NotImplementedException(msg);
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}
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return numBytes;
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}
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public virtual byte[] Read(int count)
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{
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byte[] frameBytes = new byte[count];
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int numBytesRead = 0;
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while (numBytesRead != count)
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{
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numBytesRead += StreamResource.Read(frameBytes, numBytesRead, count - numBytesRead);
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}
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return frameBytes;
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}
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internal override byte[] BuildMessageFrame(IModbusMessage message)
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{
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var messageFrame = message.MessageFrame;
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var crc = ModbusUtility.CalculateCrc(messageFrame);
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var messageBody = new MemoryStream(messageFrame.Length + crc.Length);
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messageBody.Write(messageFrame, 0, messageFrame.Length);
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messageBody.Write(crc, 0, crc.Length);
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return messageBody.ToArray();
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}
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internal override bool ChecksumsMatch(IModbusMessage message, byte[] messageFrame)
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{
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return BitConverter.ToUInt16(messageFrame, messageFrame.Length - 2) ==
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BitConverter.ToUInt16(ModbusUtility.CalculateCrc(message.MessageFrame), 0);
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}
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internal override IModbusMessage ReadResponse<T>()
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{
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byte[] frameStart = Read(ResponseFrameStartLength);
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byte[] frameEnd = Read(ResponseBytesToRead(frameStart));
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byte[] frame = Enumerable.Concat(frameStart, frameEnd).ToArray();
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Debug.WriteLine($"RX: {string.Join(", ", frame)}");
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return CreateResponse<T>(frame);
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}
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internal override byte[] ReadRequest()
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{
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byte[] frameStart = Read(RequestFrameStartLength);
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byte[] frameEnd = Read(RequestBytesToRead(frameStart));
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byte[] frame = Enumerable.Concat(frameStart, frameEnd).ToArray();
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Debug.WriteLine($"RX: {string.Join(", ", frame)}");
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return frame;
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}
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}
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}
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