使用Modbus

Question

我有一个使用Modbus协议的设备。有必要对此设备进行轮询。我有一个读取数据的功能，但是如何查看设备返回的内容？谢谢。

static void Main(string[] args)
{
    SerialPort mySerialPort = new SerialPort("COM6");
    mySerialPort.BaudRate = 19200;
    mySerialPort.Parity = Parity.None;
    mySerialPort.StopBits = StopBits.One;
    mySerialPort.DataBits = 8;
    mySerialPort.Handshake = Handshake.None;
    mySerialPort.ReadTimeout = 450;
    mySerialPort.WriteTimeout = 3000;

    mySerialPort.Open();
    mySerialPort.Write(ReadHoldingRegister(02, 1508, 1), 0, 8);
    mySerialPort.Close();           
}

public static byte[] ReadHoldingRegister(int id, int startAddress, int length)
{
    byte[] data = new byte[8];
    byte High, Low;

    data[0] = Convert.ToByte(id);
    data[1] = Convert.ToByte(3);
    byte[] _adr = BitConverter.GetBytes(startAddress - 1);
    data[2] = _adr[1];
    data[3] = _adr[0];
    byte[] _length = BitConverter.GetBytes(length);
    data[4] = _length[1];
    data[5] = _length[0];
    myCRC(data, 6, out High, out Low);
    data[6] = Low;
    data[7] = High;
    return data;
}}

我尝试使用此功能阅读。

byte[] ReadExact(Stream s, int nbytes) {
var buf = new byte[nbytes];
var readpos = 0;
while (readpos < nbytes)
    readpos += s.Read(buf, readpos, nbytes - readpos);
return buf; }

从流中读到：

byte[] response = ReadExact(serial.BaseStream, 9);

然后我尝试使用nmodbus，但我找不到任何地方如何返回数据。这是我的代码：

        SerialPort serialPort = new SerialPort();
        serialPort.PortName = "COM6";
        serialPort.BaudRate = 19200;
        serialPort.DataBits = 8;
        serialPort.Parity = Parity.None;
        serialPort.StopBits = StopBits.One;
        serialPort.Open();
        ModbusSerialMaster master = ModbusSerialMaster.CreateRtu(serialPort);
        byte slaveID = 2;
        ushort startAddress = 1508;
        ushort numOfPoints = 1;
        ushort[] holding_register = master.ReadHoldingRegisters(slaveID, startAddress, numOfPoints);
        Console.ReadKey();
        serialPort.Close();