SerialPort.BaseStream.BeginWrite＆amp; BeginRead问题

Question

我在尝试找出串行端口对象上的异步通信时遇到了一些问题，希望能得到一些帮助。我还在学习异步的东西所以要温柔:)

我基本上需要确保在写入串行端口之前缓冲区未满，并且在写入任何更多数据之前已经读取了所有数据以避免数据包冲突。不幸的是，我写的微控制器没有任何握手或CTSEnabled所以我必须在代码中模仿它。

public partial class Form2 : Form
{
    System.IO.Ports.SerialPort port = new System.IO.Ports.SerialPort();
    System.Timers.Timer tmrPolling = new System.Timers.Timer(200);
    static byte [] inputPacket = new byte[2] { (byte)255, (byte)0 }; // Byte to send to SerialPort when input polling timer is activated.

    AsyncCallback callback;
    IAsyncResult result;

    Form2()
    {
        InitializeComponent();
        port.PortName = "COM9";
        port.BaudRate = 38400;
        port.DataBits = 8;
        port.StopBits = System.IO.Ports.StopBits.One;
        port.Parity = System.IO.Ports.Parity.None;
        port.ReadTimeout = 1;
        port.ReceivedBytesThreshold = 5;
        port.DataReceived += new System.IO.Ports.SerialDataReceivedEventHandler(port_DataReceived);
        callback = new AsyncCallback(ReadComplete);  
        port.ReadBufferSize = (byte)60;
        port.WriteBufferSize = (byte)60;
        port.Open();  
        tmrPolling.Elapsed += new System.Timers.ElapsedEventHandler(tmrPolling_Elapsed);
    }

    void WritePacket(byte[] packet)
    {
        result = port.BaseStream.BeginWrite(packet, 0, packet.Count(), callback, port); // writes the input packet to the SerialPort - needed to read the IO values
    }

    void ReadComplete(IAsyncResult result)
    {

    }


    void tmrPolling_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
    {  
        WritePacket(inputPacket); // writes the input packet to the SerialPort - needed to read the IO values
    }

    void port_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
    {
        port.BaseStream.EndWrite(result);
        // Reads the data coming in from the serial port and calls the thread safe delegate to update the values on the form.
        byte [] received = new byte[port.BytesToRead];
        result = port.BaseStream.BeginRead(received, 0, received.Count(), callback, port);
        port.BaseStream.EndRead(result);  
    }

    private void UpdateValues()
    {
        byte[] b = new byte[] { (byte)255, (byte)6, (byte)hsbPan.Value, (byte)vsbTilt.Value, (byte)0,  
        (byte)0, (byte)0, (byte)0, (byte)13, (byte)10 };
        WritePacket(b);
    }

    private void chkEnablePolling_CheckedChanged(object sender, EventArgs e)
    {  
        tmrPolling.Enabled = chkEnablePolling.Checked;
        test.Enabled = chkEnablePolling.Checked;
        vsbInputInterval.Enabled = chkEnablePolling.Checked;
        vsbInputInterval.Value = Convert.ToInt32(tmrPolling.Interval);
        txtInputInterval.Enabled = chkEnablePolling.Checked;
        txtInputInterval.Text = ((float)tmrPolling.Interval / ( float)1000).ToString() + " sec";
    }

    private void vsbInputInterval_Scroll(object sender, ScrollEventArgs e)
    {
        // adjusts the tick frequency of the Timer for input polling. 
        txtInputInterval.Text = ((float)tmrPolling.Interval / (float)1000).ToString() + " sec";
        tmrPolling.Interval = vsbInputInterval.Value;
    } 

    private void vsbTilt_Scroll(object sender, ScrollEventArgs e)
    {  
        UpdateValues();
    }

    private void hsbPan_Scroll(object sender, ScrollEventArgs e)
    {
        UpdateValues();
    }
}