本文讲述了C# windows API方式操作串口！具有很好的参考价值，希望对大家有所帮助。一起跟随六星小编过来看看吧，具体如下:

最近使用.Net下的SerialPort类操作串口，参数正确报错:连到系统上的设备没有发挥作用。使用C++程序调用正常，未找到问题原因，使用windows API 方式打开串口正常。

class CommPort {
	public string PortNum;
	public int BaudRate;
	public byte ByteSize;
	public byte Parity; // 0-4=no,odd,even,mark,space 
	public byte StopBits; // 0,1,2 = 1, 1.5, 2 
	public int ReadTimeout;
	
	//comm port win32 file handle
	private int hComm = -1;
	
	public bool Opened = false;
	 
	//win32 api constants
	  private const uint GENERIC_READ = 0x80000000;
	  private const uint GENERIC_WRITE = 0x40000000;
	  private const int OPEN_EXISTING = 3;		
	  private const int INVALID_HANDLE_VALUE = -1;
	
	[StructLayout(LayoutKind.Sequential)]
	public struct DCB {
		//taken from c struct in platform sdk 
		public int DCBlength;           // sizeof(DCB) 
		public int BaudRate;            // 指定当前波特率 current baud rate
		// these are the c struct bit fields, bit twiddle flag to set
		public int fBinary;          // 指定是否允许二进制模式,在windows95中必须主TRUE binary mode, no EOF check 
		public int fParity;          // 指定是否允许奇偶校验 enable parity checking 
		public int fOutxCtsFlow;      // 指定CTS是否用于检测发送控制，当为TRUE是CTS为OFF，发送将被挂起。 CTS output flow control 
		public int fOutxDsrFlow;      // 指定CTS是否用于检测发送控制 DSR output flow control 
		public int fDtrControl;       // DTR_CONTROL_DISABLE值将DTR置为OFF, DTR_CONTROL_ENABLE值将DTR置为ON, DTR_CONTROL_HANDSHAKE允许DTR"握手" DTR flow control type 
		public int fDsrSensitivity;   // 当该值为TRUE时DSR为OFF时接收的字节被忽略 DSR sensitivity 
		public int fTXContinueOnXoff; // 指定当接收缓冲区已满,并且驱动程序已经发送出XoffChar字符时发送是否停止。TRUE时，在接收缓冲区接收到缓冲区已满的字节XoffLim且驱动程序已经发送出XoffChar字符中止接收字节之后，发送继续进行。　FALSE时，在接收缓冲区接收到代表缓冲区已空的字节XonChar且驱动程序已经发送出恢复发送的XonChar之后，发送继续进行。XOFF continues Tx 
		public int fOutX;          // TRUE时，接收到XoffChar之后便停止发送接收到XonChar之后将重新开始 XON/XOFF out flow control 
		public int fInX;           // TRUE时，接收缓冲区接收到代表缓冲区满的XoffLim之后，XoffChar发送出去接收缓冲区接收到代表缓冲区空的XonLim之后，XonChar发送出去 XON/XOFF in flow control 
		public int fErrorChar;     // 该值为TRUE且fParity为TRUE时，用ErrorChar 成员指定的字符代替奇偶校验错误的接收字符 enable error replacement 
		public int fNull;          // eTRUE时，接收时去掉空（0值）字节 enable null stripping 
		public int fRtsControl;     // RTS flow control 
										/*RTS_CONTROL_DISABLE时,RTS置为OFF
		　								RTS_CONTROL_ENABLE时, RTS置为ON
									RTS_CONTROL_HANDSHAKE时,
									当接收缓冲区小于半满时RTS为ON
		　								当接收缓冲区超过四分之三满时RTS为OFF
									RTS_CONTROL_TOGGLE时,
									当接收缓冲区仍有剩余字节时RTS为ON ,否则缺省为OFF*/
		public int fAbortOnError;   // TRUE时,有错误发生时中止读和写操作 abort on error 
		public int fDummy2;        // 未使用 reserved
		public uint flags;
		public ushort wReserved;          // 未使用,必须为0 not currently used 
		public ushort XonLim;             // 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 transmit XON threshold 
		public ushort XoffLim;            // 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 transmit XOFF threshold 
		public byte ByteSize;           // 指定端口当前使用的数据位	number of bits/byte, 4-8 
		public byte Parity;             // 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 
		public byte StopBits;           // 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 
		public char XonChar;            // 指定用于发送和接收字符XON的值 Tx and Rx XON character 
		public char XoffChar;           // 指定用于发送和接收字符XOFF值 Tx and Rx XOFF character 
		public char ErrorChar;          // 本字符用来代替接收到的奇偶校验发生错误时的值 error replacement character 
		public char EofChar;            // 当没有使用二进制模式时,本字符可用来指示数据的结束 end of input character 
		public char EvtChar;            // 当接收到此字符时,会产生一个事件 received event character 
		public ushort wReserved1;         // 未使用 reserved; do not use 
	}

	[StructLayout(LayoutKind.Sequential)]
	private struct COMMTIMEOUTS {  
	  public int ReadIntervalTimeout; 
	  public int ReadTotalTimeoutMultiplier; 
	  public int ReadTotalTimeoutConstant; 
	  public int WriteTotalTimeoutMultiplier; 
	  public int WriteTotalTimeoutConstant; 
	} 	

	[StructLayout(LayoutKind.Sequential)]	
	private struct OVERLAPPED { 
	    public int  Internal; 
	    public int  InternalHigh; 
	    public int  Offset; 
	    public int  OffsetHigh; 
	    public int hEvent; 
	}  
	
	[DllImport("kernel32.dll")]
	private static extern int CreateFile(
	  string lpFileName,                         // 要打开的串口名称
	  uint dwDesiredAccess,                      // 指定串口的访问方式，一般设置为可读可写方式
	  int dwShareMode,                          // 指定串口的共享模式，串口不能共享，所以设置为0
	  int lpSecurityAttributes, // 设置串口的安全属性，WIN9X下不支持，应设为NULL
	  int dwCreationDisposition,                // 对于串口通信，创建方式只能为OPEN_EXISTING
	  int 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
	  int hTemplateFile                        // 对于串口通信必须设置为NULL
	);

     //hComm = CreateFile(PortNum ,GENERIC_READ | GENERIC_WRITE,0, 0,OPEN_EXISTING,0,0);
	[DllImport("kernel32.dll")]
	private static extern bool GetCommState(
	  int hFile,  //通信设备句柄
	  ref DCB lpDCB    // 设备控制块DCB
	);	
	[DllImport("kernel32.dll")]
	private static extern bool BuildCommDCB(
	  string lpDef,  // 设备控制字符串
	  ref DCB lpDCB     // 设备控制块
	);
	[DllImport("kernel32.dll")]
	private static extern bool SetCommState(
	  int hFile,  // 通信设备句柄
	  ref DCB lpDCB    // 设备控制块
	);
	[DllImport("kernel32.dll")]
	private static extern bool GetCommTimeouts(
	  int hFile,                  // 通信设备句柄 handle to comm device
	  ref COMMTIMEOUTS lpCommTimeouts  // 超时时间 time-out values
	);	
	[DllImport("kernel32.dll")]	
	private static extern bool SetCommTimeouts(
	  int hFile,                  // 通信设备句柄 handle to comm device
	  ref COMMTIMEOUTS lpCommTimeouts  // 超时时间 time-out values
	);
	[DllImport("kernel32.dll")]
	private static extern bool ReadFile(
	  int hFile,                // 通信设备句柄 handle to file
	  byte[] lpBuffer,             // 数据缓冲区 data buffer
	  int nNumberOfBytesToRead,  // 多少字节等待读取 number of bytes to read
	  ref int lpNumberOfBytesRead, // 读取多少字节 number of bytes read
	  ref OVERLAPPED lpOverlapped    // 溢出缓冲区 overlapped buffer
	);
	[DllImport("kernel32.dll")]	
	private static extern bool WriteFile(
	  int hFile,                    // 通信设备句柄 handle to file
	  byte[] lpBuffer,                // 数据缓冲区 data buffer
	  int nNumberOfBytesToWrite,     // 多少字节等待写入 number of bytes to write
	  ref int lpNumberOfBytesWritten,  // 已经写入多少字节 number of bytes written
	  ref OVERLAPPED lpOverlapped        // 溢出缓冲区 overlapped buffer
	);
	[DllImport("kernel32.dll")]
	private static extern bool CloseHandle(
	  int hObject   // handle to object
	);
	[DllImport("kernel32.dll")]
	private static extern uint GetLastError();
	
	public void Open()
	{
	
        DCB dcbCommPort = new DCB();
        COMMTIMEOUTS ctoCommPort = new COMMTIMEOUTS();	
	 	 
		 // 打开串口 OPEN THE COMM PORT.
        hComm = CreateFile(PortNum ,GENERIC_READ | GENERIC_WRITE,0, 0,OPEN_EXISTING,0,0);
		 // 如果串口没有打开，就打开 IF THE PORT CANNOT BE OPENED, BAIL OUT.
		if(hComm == INVALID_HANDLE_VALUE) 
		{
	  		throw(new ApplicationException("非法操作，不能打开串口！"));
		}
	
		// 设置通信超时时间 SET THE COMM TIMEOUTS.
		GetCommTimeouts(hComm,ref ctoCommPort);
		ctoCommPort.ReadTotalTimeoutConstant = ReadTimeout;
		ctoCommPort.ReadTotalTimeoutMultiplier = 0;
		ctoCommPort.WriteTotalTimeoutMultiplier = 0;
		ctoCommPort.WriteTotalTimeoutConstant = 0;  
		SetCommTimeouts(hComm,ref ctoCommPort);
	
		// 设置串口 SET BAUD RATE, PARITY, WORD SIZE, AND STOP BITS.
		GetCommState(hComm, ref dcbCommPort);
		dcbCommPort.BaudRate=BaudRate;
		dcbCommPort.flags=0;
		//dcb.fBinary=1;
		dcbCommPort.flags|=1;
		if (Parity>0)
		{
	 	  //dcb.fParity=1
	      dcbCommPort.flags|=2;
		}
		dcbCommPort.Parity=Parity;
		dcbCommPort.ByteSize=ByteSize;
		dcbCommPort.StopBits=StopBits;
		if (!SetCommState(hComm, ref dcbCommPort))
		{
		 //uint ErrorNum=GetLastError();
	     throw(new ApplicationException("非法操作，不能打开串口！"));
		}
	  //unremark to see if setting took correctly
	  //DCB dcbCommPort2 = new DCB();
	  //GetCommState(hComm, ref dcbCommPort2);
		Opened = true;
	}
	
	public void Close() {
		if (hComm!=INVALID_HANDLE_VALUE) {
			CloseHandle(hComm);
		}
	}
	
	public byte[] Read(int NumBytes) {
		byte[] BufBytes;
		byte[] OutBytes;
		BufBytes = new byte[NumBytes];
		if (hComm!=INVALID_HANDLE_VALUE) {
			OVERLAPPED ovlCommPort = new OVERLAPPED();
			int BytesRead=0;
			ReadFile(hComm,BufBytes,NumBytes,ref BytesRead,ref ovlCommPort);
			OutBytes = new byte[BytesRead];
			Array.Copy(BufBytes,OutBytes,BytesRead);
		} 
		else {
			throw(new ApplicationException("串口未打开！"));
		}
		return OutBytes;
	}
	
	public void Write(byte[] WriteBytes) {
		if (hComm!=INVALID_HANDLE_VALUE) {
			OVERLAPPED ovlCommPort = new OVERLAPPED();
			int BytesWritten = 0;
			WriteFile(hComm,WriteBytes,WriteBytes.Length,ref BytesWritten,ref ovlCommPort);
		}
		else {
			throw(new ApplicationException("串口未打开！"));
		}		
	}
}

用createfile 打开串口时，当串口号小于10时，打开正常。

当串口号大于9时则打开失败，GetLastError 返回值为2，错误提示为 系统找不到指定的文件。
原因是设备名不对。当串口小10时设备名为COMx, 当串口时大于9时为\\.\COMx

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