c#调api串口通讯 
 原文:c#调api串口通讯  
  
在调试ICU通信设备的时候,由于串口通信老出现故障,所以就怀疑CF实现的SerialPort类是否有问题,所以最后决定用纯API函数实现串口读写。
 先从网上搜索相关代码(关键字:C# API 串口),发现网上相关的资料大约来源于一个版本,那就是所谓的msdn提供的样例代码(msdn的具体出处,我没有考证),其它的代码大都是它的变种。
 其实这个示例代码是有问题的,也就是说DCB结构体声明的有问题,虽然该代码可以正常通信,不过如果你设置了奇偶校验的话,你会发现奇偶校验无效。
 VC中的DCB结构声明如下:
 typedef struct _DCB {
 DWORD DCBlength;      /* sizeof(DCB)                     */
 DWORD BaudRate;       /* Baudrate at which running       */
 DWORD fBinary: 1;     /* Binary Mode (skip EOF check)    */
 DWORD fParity: 1;     /* Enable parity checking          */
 DWORD fOutxCtsFlow:1; /* CTS handshaking on output       */
 DWORD fOutxDsrFlow:1; /* DSR handshaking on output       */
 DWORD fDtrControl:2; /* DTR Flow control                */
 DWORD fDsrSensitivity:1; /* DSR Sensitivity              */
 DWORD fTXContinueOnXoff: 1; /* Continue TX when Xoff sent */
 DWORD fOutX: 1;       /* Enable output X-ON/X-OFF        */
 DWORD fInX: 1;        /* Enable input X-ON/X-OFF         */
 DWORD fErrorChar: 1; /* Enable Err Replacement          */
 DWORD fNull: 1;       /* Enable Null stripping           */
 DWORD fRtsControl:2; /* Rts Flow control                */
 DWORD fAbortOnError:1; /* Abort all reads and writes on Error */
 DWORD fDummy2:17;     /* Reserved                        */
 WORD wReserved;       /* Not currently used              */
 WORD XonLim;          /* Transmit X-ON threshold         */
 WORD XoffLim;         /* Transmit X-OFF threshold        */
 BYTE ByteSize;        /* Number of bits/byte, 4-8        */
 BYTE Parity;          /* 0-4=None,Odd,Even,Mark,Space    */
 BYTE StopBits;        /* 0,1,2 = 1, 1.5, 2               */
 char XonChar;         /* Tx and Rx X-ON character        */
 char XoffChar;        /* Tx and Rx X-OFF character       */
 char ErrorChar;       /* Error replacement char          */
 char EofChar;         /* End of Input character          */
 char EvtChar;         /* Received Event character        */
 WORD wReserved1;      /* Fill for now.                   */
 } DCB, *LPDCB;
  有问题的代码DCB结构声明如下:
 [StructLayout(LayoutKind.Sequential)]
         public struct DCB
         {
             public int DCBlength;
             public int BaudRate;
             public int fBinary;
             public int fParity;
             public int fOutxCtsFlow;
             public int fOutxDsrFlow;
             public int fDtrControl;
             public int fDsrSensitivity;
             public int fTXContinueOnXoff;
             public int fOutX;
             public int fInX;
             public int fErrorChar;
             public int fNull;
             public int fRtsControl;
             public int fAbortOnError;
             public int fDummy2;
             public uint flags;
             public ushort wReserved;
             public ushort XonLim;
             public ushort XoffLim;
             public byte ByteSize;
             public byte Parity;
             public byte StopBits;
             public byte XonChar;
             public byte XoffChar;
             public byte ErrorChar;
             public byte EofChar;
             public byte EvtChar;
             public ushort wReserved1;
         }
 对C++比较熟悉网友应该知道,结构体中这种格式的声明,如DWORD fBinary: 1;是以位为单位进行变量设置的,DCB中相关位一共占4个字节,也就是相当于C#中的一个int变量所占的空间。很明显上面的DCB结构会有问题,实际上后面你设置的串口参数,如奇偶校验由于偏移有问题,虽然你设置了,其实都没有设置成功。
 其实也不是我说人家的DCB声明错了就错了,在SerialPort类中你就可以找到微软官方自己的DCB声明(需要反编译SerialPort类),声明如下:
 [StructLayout(LayoutKind.Sequential)]
         public struct DCB
         {
             public int DCBlength;
             public int BaudRate;
             public uint Flags;
             public ushort wReserved;
             public ushort XonLim;
             public ushort XoffLim;
             public byte ByteSize;
             public byte Parity;
             public byte StopBits;
             public byte XonChar;
             public byte XoffChar;
             public byte ErrorChar;
             public byte EofChar;
             public byte EvtChar;
             public ushort wReserved1;
         }
 并且专门有一个设置位标志的函数,如下:
 internal void SetDcbFlag(int whichFlag, int setting)
         {
             uint num;
             setting = setting << whichFlag;
             if ((whichFlag == 4) || (whichFlag == 12))
             {
                 num = 3;
             }
             else if (whichFlag == 15)
             {
                 num = 0x1ffff;
             }
             else
             {
                 num = 1;
             }
             dcb.flags &= ~(num << whichFlag);
             dcb.flags |= (uint)setting;
         }
 经过修改能正确运行的API代码如下(注意,由于我是在WinCE平台上运行,所以DLL的路径为"//windows//coredll.dll",你修改为"kernel32"后即可在PC机使用):
 ///<summary>
     /// API串口类 叶帆修改 http://blog.csdn.net/yefanqiu
     ///</summary>
     public class CommPort
     {
         ///<summary>
         ///端口名称(COM1,COM2...COM4...)
         ///</summary>
         public string Port = "COM1:";
         ///<summary>
         ///波特率9600
         ///</summary>
         public int BaudRate = 9600;
         ///<summary>
         ///数据位4-8
         ///</summary>
         public byte ByteSize = 8; //4-8 
         ///<summary>
         ///奇偶校验0-4=no,odd,even,mark,space 
         ///</summary>
         public byte Parity = 0;   //0-4=no,odd,even,mark,space 
         ///<summary>
         ///停止位
         ///</summary>
         public byte StopBits = 0;   //0,1,2 = 1, 1.5, 2 
         ///<summary>
         ///超时长
         ///</summary>
         public int ReadTimeout = 200;
         ///<summary>
         ///串口是否已经打开
         ///</summary>
         public bool Opened = false;
         ///<summary>
         /// COM口句柄
         ///</summary>
         private int hComm = -1;
          #region "API相关定义"
         private const string DLLPATH = "//windows//coredll.dll"; // "kernel32";
          ///<summary>
         /// WINAPI常量,写标志
         ///</summary>
         private const uint GENERIC_READ = 0x80000000;
         ///<summary>
         /// WINAPI常量,读标志
         ///</summary>
         private const uint GENERIC_WRITE = 0x40000000;
         ///<summary>
         /// WINAPI常量,打开已存在
         ///</summary>
         private const int OPEN_EXISTING = 3;
         ///<summary>
         /// WINAPI常量,无效句柄
         ///</summary>
         private const int INVALID_HANDLE_VALUE = -1;
          private const int PURGE_RXABORT = 0x2;
         private const int PURGE_RXCLEAR = 0x8;
         private const int PURGE_TXABORT = 0x1;
         private const int PURGE_TXCLEAR = 0x4;
          ///<summary>
         ///设备控制块结构体类型
         ///</summary>
         [StructLayout(LayoutKind.Sequential)]
         public struct DCB
         {
            ///<summary>
             /// DCB长度
             ///</summary>
             public int DCBlength;
             ///<summary>
             ///指定当前波特率
             ///</summary>
             public int BaudRate;
             ///<summary>
             ///标志位
             ///</summary>
             public uint flags;
             ///<summary>
             ///未使用,必须为0
             ///</summary>
             public ushort wReserved;
             ///<summary>
             ///指定在XON字符发送这前接收缓冲区中可允许的最小字节数
             ///</summary>
             public ushort XonLim;
             ///<summary>
             ///指定在XOFF字符发送这前接收缓冲区中可允许的最小字节数
             ///</summary>
             public ushort XoffLim;
             ///<summary>
             ///指定端口当前使用的数据位
             ///</summary>
             public byte ByteSize;
             ///<summary>
             ///指定端口当前使用的奇偶校验方法,可能为:EVENPARITY,MARKPARITY,NOPARITY,ODDPARITY 0-4=no,odd,even,mark,space 
             ///</summary>
             public byte Parity;
             ///<summary>
             ///指定端口当前使用的停止位数,可能为:ONESTOPBIT,ONE5STOPBITS,TWOSTOPBITS 0,1,2 = 1, 1.5, 2 
             ///</summary>
             public byte StopBits;
             ///<summary>
             ///指定用于发送和接收字符XON的值 Tx and Rx XON character 
             ///</summary>
             public byte XonChar;
             ///<summary>
             ///指定用于发送和接收字符XOFF值 Tx and Rx XOFF character 
             ///</summary>
             public byte XoffChar;
             ///<summary>
             ///本字符用来代替接收到的奇偶校验发生错误时的值
             ///</summary>
             public byte ErrorChar;
             ///<summary>
             ///当没有使用二进制模式时,本字符可用来指示数据的结束
             ///</summary>
             public byte EofChar;
             ///<summary>
             ///当接收到此字符时,会产生一个事件
             ///</summary>
             public byte EvtChar;
             ///<summary>
             ///未使用
             ///</summary>
             public ushort wReserved1;
         }
          ///<summary>
         ///串口超时时间结构体类型
         ///</summary>
         [StructLayout(LayoutKind.Sequential)]
         private struct COMMTIMEOUTS
         {
             public int ReadIntervalTimeout;
             public int ReadTotalTimeoutMultiplier;
             public int ReadTotalTimeoutConstant;
             public int WriteTotalTimeoutMultiplier;
             public int WriteTotalTimeoutConstant;
         }
          ///<summary>
         ///溢出缓冲区结构体类型
         ///</summary>
         [StructLayout(LayoutKind.Sequential)]
         private struct OVERLAPPED
         {
             public int Internal;
             public int InternalHigh;
             public int Offset;
             public int OffsetHigh;
             public int hEvent;
         }
          ///<summary>
         ///打开串口
         ///</summary>
         ///<param name="lpFileName">要打开的串口名称</param>
         ///<param name="dwDesiredAccess">指定串口的访问方式,一般设置为可读可写方式</param>
         ///<param name="dwShareMode">指定串口的共享模式,串口不能共享,所以设置为0</param>
         ///<param name="lpSecurityAttributes">设置串口的安全属性,WIN9X下不支持,应设为NULL</param>
         ///<param name="dwCreationDisposition">对于串口通信,创建方式只能为OPEN_EXISTING</param>
         ///<param name="dwFlagsAndAttributes">指定串口属性与标志,设置为FILE_FLAG_OVERLAPPED(重叠I/O操作),指定串口以异步方式通信</param>
         ///<param name="hTemplateFile">对于串口通信必须设置为NULL</param>
         [DllImport(DLLPATH)]
         private static extern int CreateFile(string lpFileName, uint dwDesiredAccess, int dwShareMode,
         int lpSecurityAttributes, int dwCreationDisposition, int dwFlagsAndAttributes, int hTemplateFile);
          ///<summary>
         ///得到串口状态
         ///</summary>
         ///<param name="hFile">通信设备句柄</param>
         ///<param name="lpDCB">设备控制块DCB</param>
         [DllImport(DLLPATH)]
         private static extern bool GetCommState(int hFile, ref DCB lpDCB);
          ///<summary>
         ///建立串口设备控制块(嵌入版没有)
         ///</summary>
         ///<param name="lpDef">设备控制字符串</param>
         ///<param name="lpDCB">设备控制块</param>
         //[DllImport(DLLPATH)]
         //private static extern bool BuildCommDCB(string lpDef, ref DCB lpDCB);
          ///<summary>
         ///设置串口状态
         ///</summary>
         ///<param name="hFile">通信设备句柄</param>
         ///<param name="lpDCB">设备控制块</param>
         [DllImport(DLLPATH)]
         private static extern bool SetCommState(int hFile, ref DCB lpDCB);
          ///<summary>
         ///读取串口超时时间
         ///</summary>
         ///<param name="hFile">通信设备句柄</param>
         ///<param name="lpCommTimeouts">超时时间</param>
         [DllImport(DLLPATH)]
         private static extern bool GetCommTimeouts(int hFile, ref COMMTIMEOUTS lpCommTimeouts);
          ///<summary>
         ///设置串口超时时间
         ///</summary>
         ///<param name="hFile">通信设备句柄</param>
         ///<param name="lpCommTimeouts">超时时间</param>
         [DllImport(DLLPATH)]
         private static extern bool SetCommTimeouts(int hFile, ref COMMTIMEOUTS lpCommTimeouts);
          ///<summary>
         ///读取串口数据
         ///</summary>
         ///<param name="hFile">通信设备句柄</param>
         ///<param name="lpBuffer">数据缓冲区</param>
         ///<param name="nNumberOfBytesToRead">多少字节等待读取</param>
         ///<param name="lpNumberOfBytesRead">读取多少字节</param>
         ///<param name="lpOverlapped">溢出缓冲区</param>
         [DllImport(DLLPATH)]
         private static extern bool ReadFile(int hFile, byte[] lpBuffer, int nNumberOfBytesToRead,
         ref int lpNumberOfBytesRead, ref OVERLAPPED lpOverlapped);
          ///<summary>
         ///写串口数据
         ///</summary>
         ///<param name="hFile">通信设备句柄</param>
         ///<param name="lpBuffer">数据缓冲区</param>
         ///<param name="nNumberOfBytesToWrite">多少字节等待写入</param>
         ///<param name="lpNumberOfBytesWritten">已经写入多少字节</param>
         ///<param name="lpOverlapped">溢出缓冲区</param>
         [DllImport(DLLPATH)]
         private static extern bool WriteFile(int hFile, byte[] lpBuffer, int nNumberOfBytesToWrite,
         ref int lpNumberOfBytesWritten, ref OVERLAPPED lpOverlapped);
          [DllImport(DLLPATH, SetLastError = true)]
         private static extern bool FlushFileBuffers(int hFile);
          [DllImport(DLLPATH, SetLastError = true)]
         private static extern bool PurgeComm(int hFile, uint dwFlags);
          ///<summary>
         ///关闭串口
         ///</summary>
         ///<param name="hObject">通信设备句柄</param>
         [DllImport(DLLPATH)]
         private static extern bool CloseHandle(int hObject);
          ///<summary>
         ///得到串口最后一次返回的错误
         ///</summary>
         [DllImport(DLLPATH)]
         private static extern uint GetLastError();
         #endregion
          ///<summary>
         ///设置DCB标志位
         ///</summary>
         ///<param name="whichFlag"></param>
         ///<param name="setting"></param>
         ///<param name="dcb"></param>
         internal void SetDcbFlag(int whichFlag, int setting, DCB dcb)
         {
             uint num;
             setting = setting << whichFlag;
             if ((whichFlag == 4) || (whichFlag == 12))
             {
                 num = 3;
             }
             else if (whichFlag == 15)
             {
                 num = 0x1ffff;
             }
             else
             {
                 num = 1;
             }
             dcb.flags &= ~(num << whichFlag);
             dcb.flags |= (uint)setting;
         }
          ///<summary>
         ///建立与串口的连接
         ///</summary>
         public int Open()
         {
             DCB dcb = new DCB();
             COMMTIMEOUTS ctoCommPort = new COMMTIMEOUTS();
              // 打开串口 
             hComm = CreateFile(Port, GENERIC_READ | GENERIC_WRITE, 0, 0, OPEN_EXISTING, 0, 0);
             if (hComm == INVALID_HANDLE_VALUE)
             {
                 return -1;
             }
             // 设置通信超时时间
             GetCommTimeouts(hComm, ref ctoCommPort);
             ctoCommPort.ReadTotalTimeoutConstant = ReadTimeout;
             ctoCommPort.ReadTotalTimeoutMultiplier = 0;
             ctoCommPort.WriteTotalTimeoutMultiplier = 0;
             ctoCommPort.WriteTotalTimeoutConstant = 0;
             SetCommTimeouts(hComm, ref ctoCommPort);
              //设置串口参数
             GetCommState(hComm, ref dcb);
             dcb.DCBlength = Marshal.SizeOf(dcb);
             dcb.BaudRate = BaudRate;
             dcb.flags = 0;
             dcb.ByteSize = (byte)ByteSize;
             dcb.StopBits = StopBits;
             dcb.Parity = (byte)Parity;
              //------------------------------
             SetDcbFlag(0, 1, dcb);            //二进制方式 
             SetDcbFlag(1, (Parity == 0) ? 0 : 1, dcb);
             SetDcbFlag(2, 0, dcb);            //不用CTS检测发送流控制
             SetDcbFlag(3, 0, dcb);            //不用DSR检测发送流控制
             SetDcbFlag(4, 0, dcb);            //禁止DTR流量控制
             SetDcbFlag(6, 0, dcb);            //对DTR信号线不敏感
             SetDcbFlag(9, 1, dcb);            //检测接收缓冲区
             SetDcbFlag(8, 0, dcb);            //不做发送字符控制
             SetDcbFlag(10, 0, dcb);           //是否用指定字符替换校验错的字符
             SetDcbFlag(11, 0, dcb);           //保留NULL字符
             SetDcbFlag(12, 0, dcb);           //允许RTS流量控制
             SetDcbFlag(14, 0, dcb);           //发送错误后,继续进行下面的读写操作
             //--------------------------------
             dcb.wReserved = 0;                       //没有使用,必须为0       
             dcb.XonLim = 0;                          //指定在XOFF字符发送之前接收到缓冲区中可允许的最小字节数
             dcb.XoffLim = 0;                         //指定在XOFF字符发送之前缓冲区中可允许的最小可用字节数
             dcb.XonChar = 0;                         //发送和接收的XON字符 
             dcb.XoffChar = 0;                        //发送和接收的XOFF字符
             dcb.ErrorChar = 0;                       //代替接收到奇偶校验错误的字符 
             dcb.EofChar = 0;                         //用来表示数据的结束      
             dcb.EvtChar = 0;                         //事件字符,接收到此字符时,会产生一个事件        
             dcb.wReserved1 = 0;                      //没有使用 
              if (!SetCommState(hComm, ref dcb))
             {
                 return -2;
             }
             Opened = true;
             return 0;
         }
         ///<summary>
         ///关闭串口,结束通讯
         ///</summary>
         public void Close()
         {
             if (hComm != INVALID_HANDLE_VALUE)
             {
                 CloseHandle(hComm);
             }
         }
         ///<summary>
         ///读取串口返回的数据
         ///</summary>
         ///<param name="NumBytes">数据长度</param>
         public int Read(ref byte[] bytData, int NumBytes)
         {
             if (hComm != INVALID_HANDLE_VALUE)
             {
                 OVERLAPPED ovlCommPort = new OVERLAPPED();
                 int BytesRead = 0;
                 ReadFile(hComm, bytData, NumBytes, ref BytesRead, ref ovlCommPort);
                 return BytesRead;
             }
             else
             {
                 return -1;
             }
         }
          ///<summary>
         ///向串口写数据
         ///</summary>
         ///<param name="WriteBytes">数据数组</param>
         public int Write(byte[] WriteBytes, int intSize)
         {
             if (hComm != INVALID_HANDLE_VALUE)
             {
                 OVERLAPPED ovlCommPort = new OVERLAPPED();
                 int BytesWritten = 0;
                 WriteFile(hComm, WriteBytes, intSize, ref BytesWritten, ref ovlCommPort);
                 return BytesWritten;
             }
             else
             {
                 return -1;
             }
         }
          ///<summary>
         ///清除接收缓冲区
         ///</summary>
         ///<returns></returns>
         public void ClearReceiveBuf()
         {
             if (hComm != INVALID_HANDLE_VALUE)
             {
                 PurgeComm(hComm, PURGE_RXABORT | PURGE_RXCLEAR);
             }
         }
          ///<summary>
         ///清除发送缓冲区
         ///</summary>
         public void ClearSendBuf()
         {
             if (hComm != INVALID_HANDLE_VALUE)
             {
                 PurgeComm(hComm, PURGE_TXABORT | PURGE_TXCLEAR);
             }
         }
  }
 后记:我的串口程序修改为API方式后,实际发现与SerialPort类遇到同样的问题,所以SerialPort类还是值得信任的。该API方式的代码在WinCE平台和PC平台都调试通过。
   posted on 2018-09-30 08:58 NET未来之路 阅读(...) 评论(...) 编辑 收藏