串行端口-如何设置字符

本文关键字：设置 字符 何设置 串行端口 | 更新日期: 2023-09-27 18:22:08

考虑：

Baud rate 19200
RTS on
DTR on
Data bits=8, Stop bits=1, Parity=None
Set chars: Eof=0x00, Error=0x2A, Break=0x2A, Event=0x00, Xon=0x11, Xoff=0x13
Handflow: ControlHandShake=(DTR_CONTROL), FlowReplace=(TRANSMIT_TOGGLE, RTS_CONTROL),
XonLimit=0, XoffLimit=4096

好的，所以使用端口扫描仪，我发现USB设备需要这些设置来方便导入。我可以按照如下方式重新创建其中的大部分：

port = new SerialPort("COM4");
port.DtrEnable = true;
port.RtsEnable = true;
port.Handshake = Handshake.None;                                  
port.BaudRate = 19200;
port.StopBits = StopBits.One;
port.Parity = Parity.None;
port.DataBits = 8;    
port.Open();
byte[] a = new byte[2] { 0x0 , 0x1 };
port.Write(a, 0, 1);
port.Write(a, 0, 1);
port.Write("mem");
port.Write("mem");
string output = port.ReadExisting();
System.Diagnostics.Debug.WriteLine("Found: " + output);

然而，产生的代码是：

Set chars: Eof=0x1A, Error=0x00, Break=0x00, Event=0x1A, Xon=0x11, Xoff=0x13
XonLimit=1024, XoffLimit=1024

如何更改X限制和每个字符代码，以便有机会工作？

postSerialPort 0x1A字符读取问题是我迄今为止发现的最接近的问题，但我不理解。

串行端口-如何设置字符

您可以在C#中为serialPort添加扩展-请参阅NET2.0 serialPort class中的Xon/Xoff值。

对于其他可以更改的字段：

dcbType.GetField("XonChar"); // "XonChar", "XoffChar", "ErrorChar", "EofChar", "EvtChar"

代码：

using System;
using System.ComponentModel;
using System.IO.Ports;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Security;
using System.Security.Permissions;
using Microsoft.Win32.SafeHandles;
class Program
{
    static void Main(string[] args)
    {
        using (var port = new SerialPort("COM1"))
        {
            port.Open();
            port.SetXonXoffChars(0x12, 0x14);
        }
    }
}
internal static class SerialPortExtensions
{
    [SecurityPermission(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.UnmanagedCode)]
    public static void SetXonXoffChars(this SerialPort port, byte xon, byte xoff)
    {
        if (port == null)
            throw new NullReferenceException();
        if (port.BaseStream == null)
            throw new InvalidOperationException("Cannot change X chars until after the port has been opened.");
        try
        {
            // Get the base stream and its type which is System.IO.Ports.SerialStream
            object baseStream = port.BaseStream;
            Type baseStreamType = baseStream.GetType();
            // Get the Win32 file handle for the port
            SafeFileHandle portFileHandle = (SafeFileHandle)baseStreamType.GetField("_handle", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(baseStream);
            // Get the value of the private DCB field (a value type)
            FieldInfo dcbFieldInfo = baseStreamType.GetField("dcb", BindingFlags.NonPublic | BindingFlags.Instance);
            object dcbValue = dcbFieldInfo.GetValue(baseStream);
            // The type of dcb is Microsoft.Win32.UnsafeNativeMethods.DCB which is an internal type. We can only access it through reflection.
            Type dcbType = dcbValue.GetType();
            dcbType.GetField("XonChar").SetValue(dcbValue, xon);
            dcbType.GetField("XoffChar").SetValue(dcbValue, xoff);
            // We need to call SetCommState but because dcbValue is a private type, we don't have enough
            //  information to create a p/Invoke declaration for it. We have to do the marshalling manually.
            // Create unmanaged memory to copy DCB into
            IntPtr hGlobal = Marshal.AllocHGlobal(Marshal.SizeOf(dcbValue));
            try
            {
                // Copy their DCB value to unmanaged memory
                Marshal.StructureToPtr(dcbValue, hGlobal, false);
                // Call SetCommState
                if (!SetCommState(portFileHandle, hGlobal))
                    throw new Win32Exception(Marshal.GetLastWin32Error());
                // Update the BaseStream.dcb field if SetCommState succeeded
                dcbFieldInfo.SetValue(baseStream, dcbValue);
            }
            finally
            {
                if (hGlobal != IntPtr.Zero)
                    Marshal.FreeHGlobal(hGlobal);
            }
        }
        catch (SecurityException) { throw; }
        catch (OutOfMemoryException) { throw; }
        catch (Win32Exception) { throw; }
        catch (Exception ex)
        {
            throw new ApplicationException("SetXonXoffChars has failed due to incorrect assumptions about System.IO.Ports.SerialStream which is an internal type.", ex);
        }
    }
    [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern bool SetCommState(SafeFileHandle hFile, IntPtr lpDCB);
}

这些设置可以由Win32 SetCommState函数配置。

不幸的是，.NET没有提供一组很好的属性来配置它们，也没有提供对HANDLE的访问权限，因此您不能使用p/invoke来调整.NET SerialPort类的设置。

相反，您将不得不放弃整个System.IO.Ports.SerialPort类，并使用Win32 API:进行所有操作

  • CreateFile
  • GetCommState
  • SetCommState
  • WriteFile(Ex)
  • ReadFile(Ex)
  • WaitCommEvent

我建议您不要使用C#，Win32 API更容易从C++使用，并且使用C++/CLI，您可以编写与C#GUI良好交互的类。这是一项相当多的工作，好处是Win32串行端口函数比.NET库提供的功能强大得多。我希望有一天能被允许发布我制作的C++/CLI串行端口类。

相关文章：