向串口发送和接收数据

Question

我有一台麦哲伦扫描仪/秤。它通过rs232连接到我的电脑。当我在 ComTestSerial 程序上发送命令“S11”时，我收到重量。但是，使用我的 vb.net 代码，我无法收到响应。结果我得到了一个 TimeoutException。

发送命令的文件：

Dim yy() As Byte = System.Text.Encoding.ASCII.GetBytes("S11" & vbLf)
Me.Port.Send(yy)
Dim input = Me.Port.Receive
Return Me.ExtractMeasurement(input)

从串口读写的文件：

public void Send(byte b)
    {
        byte[] bytes = new byte[1] { b };
        this.Send(bytes);
    }

    public void Send(byte[] bytes)
    {
        this.Send(bytes, 0, bytes.Length);
    }

    public void Send(byte[] bytes, int offset, int count)
    {
        this._port.Write(bytes, offset, count);
    }

    public byte[] Receive()
    {
        int attempts = 1;
        Boolean dataReceived;

        try
        {
            while (!this.DataReceived && this._port.BytesToRead == 0 && attempts < 15)
            {
                System.Threading.Thread.Sleep(100);
                attempts++;
            }
        }
        finally
        {
            dataReceived = this.DataReceived;
            this.DataReceived = false;
        }

        if (!dataReceived && this._port.BytesToRead == 0) throw new TimeoutException();

        byte[] bytes = new byte[this._port.BytesToRead];
        this._port.Read(bytes, 0, bytes.Length);

        return bytes;
    }

我不明白为什么在 this._port.Write(bytes, offset, count); 之后 BytesToRead 和 BytesToWrite 保持为 0;

这里是 serialportconfig.xml 文件

<PortName>COM3:</PortName>
<BaudRate>Baud_9600</BaudRate>
<DataBits>Eight</DataBits>
<Parity>None</Parity>
<StopBits>One</StopBits>
<FlowCtrl>CtsRts</FlowCtrl>

更新：我发现如果我发送 vbCr 而不是 vbLf 我有时会得到正确的响应。但问题是有时。我有时会收到 TimeoutException，有时会收到响应。我正在使用从 RS232 到 USB 的适配器。会不会是这个问题？

以下是与串口相关的所有代码：

public class SerialPortAdapter
{
    #region Private Members

    private System.IO.Ports.SerialPort _port;

    private Object _dataReceivedLock = new Object();
    private Boolean _dataReceived;

    #endregion

    #region Constructor/Destructor

    public SerialPortAdapter(SerialCnfg config)
    {
        if (string.IsNullOrEmpty(config.PortName))
        {
            this._port = new System.IO.Ports.SerialPort();
        }
        else
        {
            string portName = config.PortName.TrimEnd(':');
            this._port = new System.IO.Ports.SerialPort(portName);
        }

        this._port.WriteTimeout = 2000;
        this._port.ReadTimeout = 2000;
        this._port.SetBaudRate(config.BaudRate);
        this._port.SetDataBits(config.DataBits);
        this._port.SetStopBits(config.StopBits);
        this._port.SetHandshake(config.FlowCtrl);
        this._port.SetParity(config.Parity);
    }

    ~SerialPortAdapter()
    {
        this.Close();
        this._port = null;
    }

    #endregion

    #region Public Properties

    public Boolean IsOpen
    {
        get { return this._port.IsOpen; }
    }

    public System.Text.Encoding Encoding
    {
        get { return this._port.Encoding; }
        set { this._port.Encoding = value; }
    }

    #endregion

    #region Public Methods

    public void Open()
    {
        if (this.IsOpen) return;

        this.DataReceived = false;
        this.AttachPortHandlers();
        this._port.Open();
    }

    public void Close()
    {
        if (!this.IsOpen) return;

        this._port.Close();
        this.DetachPortHandlers();
        this.DataReceived = false;
    }

    public void Send(byte b)
    {
        byte[] bytes = new byte[1] { b };
        this.Send(bytes);
    }

    public void Send(byte[] bytes)
    {
        this.Send(bytes, 0, bytes.Length);
    }

    public void Send(byte[] bytes, int offset, int count)
    {
        this._port.Write(bytes, offset, count);
    }

    public byte[] Receive()
    {
        int attempts = 1;
        Boolean dataReceived;

        try
        {
            while (!this.DataReceived && this._port.BytesToRead == 0 && attempts < 15)
            {
                System.Threading.Thread.Sleep(100);
                attempts++;
            }
        }
        finally
        {
            dataReceived = this.DataReceived;
            this.DataReceived = false;
        }

        if (!dataReceived && this._port.BytesToRead == 0) throw new TimeoutException();

        byte[] bytes = new byte[this._port.BytesToRead];
        this._port.Read(bytes, 0, bytes.Length);

        return bytes;
    }

    #endregion

    #region Private Properties

    private Boolean DataReceived
    {
        get
        {
            lock (this._dataReceivedLock)
            {
                return this._dataReceived;
            }
        }
        set
        {
            lock (this._dataReceivedLock)
            {
                this._dataReceived = value;
            }
        }
    }

    #endregion

    #region Initialization/Finalization

    private void AttachPortHandlers()
    {
        this._port.DataReceived += new System.IO.Ports.SerialDataReceivedEventHandler(this.OnDataReceived);
    }

    private void DetachPortHandlers()
    {
        this._port.DataReceived -= new System.IO.Ports.SerialDataReceivedEventHandler(this.OnDataReceived);
    }

    #endregion

    #region Event Handlers

    private void OnDataReceived(Object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
    {
        this.DataReceived = true;
    }

    #endregion
}

Answer 1

根据您发布的代码，您正在尝试处理自己的超时异常。 SerialPort 类有自己的内置超时（即，ReadTimeout、WriteTimeout），您可以在构造函数中设置这些超时。因此，您不需要其他方法来处理超时，因为它是多余的。此外，请远离 System.Threading.Sleep 方法，因为它可能会浪费大量资源Why is Thread.Sleep so harmful。

我建议你稍微重构一下你的代码，以摆脱自我强加的 Throw TimeoutException。

这里只是一个建议：

public byte[] Receive()
{
    
    try
    {
        byte[] bytes = new byte[]{};

        while(_port.BytesToRead > 0)
        {
            bytes = new byte[this._port.BytesToRead];
            this._port.Read(bytes, 0, bytes.Length);
        }
    }
    catch (TimeoutException ex)
    {
       Console.WriteLine(ex.Message);
    }
    finally
    {
        this.DataReceived = false;
    }

    return bytes;
}

Answer 2

如果您重新发送请求重量的命令（S11），麦哲伦似乎可以工作。所以对我来说解决方案是每当我在 this._port.Write(bytes, offset, count) 之后有 _port.bytesToRead=0 时，然后我重新发送命令 S11。最终，它会响应正确的结果。