异步串口类

【实例简介】

高性能串口异步通信类。
【实例截图】
【核心代码】

BOOL CSerialPort::InitPort(CWnd* pPortOwner, // the owner (CWnd) of the port (receives message)
         UINT  portnr,  // portnumber (1..4)
         UINT  baud,   // baudrate
         char  parity,  // parity
         UINT  databits,  // databits
         UINT  stopbits,  // stopbits
         DWORD dwCommEvents, // EV_RXCHAR, EV_CTS etc
         UINT  writebuffersize) // size to the writebuffer
{
 assert(portnr > 0 && portnr < 5);
 assert(pPortOwner != NULL);

 // if the thread is alive: Kill
 if (m_bThreadAlive)
 {
  do
  {
   SetEvent(m_hShutdownEvent);
  } while (m_bThreadAlive);
  TRACE("Thread ended\n");
 }

 // create events
 if (m_ov.hEvent != NULL)
  ResetEvent(m_ov.hEvent);
 else
  m_ov.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);

 if (m_hWriteEvent != NULL)
  ResetEvent(m_hWriteEvent);
 else
  m_hWriteEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
 
 if (m_hShutdownEvent != NULL)
  ResetEvent(m_hShutdownEvent);
 else
  m_hShutdownEvent = CreateEvent(NULL, TRUE, FALSE, NULL);

 // initialize the event objects
 m_hEventArray[0] = m_hShutdownEvent; // highest priority
 m_hEventArray[1] = m_ov.hEvent;
 m_hEventArray[2] = m_hWriteEvent;

 // initialize critical section
 InitializeCriticalSection(&m_csCommunicationSync);
 
 // set buffersize for writing and save the owner
 m_pOwner = pPortOwner;

 if (m_szWriteBuffer != NULL)
  delete [] m_szWriteBuffer;
 m_szWriteBuffer = new char[writebuffersize];

 m_nPortNr = portnr;

 m_nWriteBufferSize = writebuffersize;
 m_dwCommEvents = dwCommEvents;

 BOOL bResult = FALSE;
 char *szPort = new char[50];
 char *szBaud = new char[50];

 // now it critical!
 EnterCriticalSection(&m_csCommunicationSync);

 // if the port is already opened: close it
 if (m_hComm != NULL)
 {
  CloseHandle(m_hComm);
  m_hComm = NULL;
 }

 // prepare port strings
 sprintf(szPort, "COM%d", portnr);
 sprintf(szBaud, "baud=%d parity=%c data=%d stop=%d", baud, parity, databits, stopbits);

 // get a handle to the port
 m_hComm = CreateFile(szPort,      // communication port string (COMX)
          GENERIC_READ | GENERIC_WRITE, // read/write types
          0,        // comm devices must be opened with exclusive access
          NULL,       // no security attributes
          OPEN_EXISTING,     // comm devices must use OPEN_EXISTING
          FILE_FLAG_OVERLAPPED,   // Async I/O
          0);       // template must be 0 for comm devices

 if (m_hComm == INVALID_HANDLE_VALUE)
 {
  // port not found
  delete [] szPort;
  delete [] szBaud;

  return FALSE;
 }

 // set the timeout values
 m_CommTimeouts.ReadIntervalTimeout = 1000;
 m_CommTimeouts.ReadTotalTimeoutMultiplier = 1000;
 m_CommTimeouts.ReadTotalTimeoutConstant = 1000;
 m_CommTimeouts.WriteTotalTimeoutMultiplier = 1000;
 m_CommTimeouts.WriteTotalTimeoutConstant = 1000;

 // configure
 if (SetCommTimeouts(m_hComm, &m_CommTimeouts))
 {        
  if (SetCommMask(m_hComm, dwCommEvents))
  {
   if (GetCommState(m_hComm, &m_dcb))
   {
    m_dcb.fRtsControl = RTS_CONTROL_ENABLE;  // set RTS bit high!
    if (BuildCommDCB(szBaud, &m_dcb))
    {
     if (SetCommState(m_hComm, &m_dcb))
      ; // normal operation... continue
     else
      ProcessErrorMessage("SetCommState()");
    }
    else
     ProcessErrorMessage("BuildCommDCB()");
   }
   else
    ProcessErrorMessage("GetCommState()");
  }
  else
   ProcessErrorMessage("SetCommMask()");
 }
 else
  ProcessErrorMessage("SetCommTimeouts()");

 delete [] szPort;
 delete [] szBaud;

 // flush the port
 PurgeComm(m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT);

 // release critical section
 LeaveCriticalSection(&m_csCommunicationSync);

 TRACE("Initialisation for communicationport %d completed.\nUse Startmonitor to communicate.\n", portnr);

 return TRUE;
}

UINT CSerialPort::CommThread(LPVOID pParam)
{
 // Cast the void pointer passed to the thread back to
 // a pointer of CSerialPort class
 CSerialPort *port = (CSerialPort*)pParam;
 
 // Set the status variable in the dialog class to
 // TRUE to indicate the thread is running.
 port->m_bThreadAlive = TRUE; 
  
 // Misc. variables
 DWORD BytesTransfered = 0;
 DWORD Event = 0;
 DWORD CommEvent = 0;
 DWORD dwError = 0;
 COMSTAT comstat;
 BOOL  bResult = TRUE;
  
 // Clear comm buffers at startup
 if (port->m_hComm)  // check if the port is opened
  PurgeComm(port->m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT);

 // begin forever loop.  This loop will run as long as the thread is alive.
 for (;;)
 {

  // Make a call to WaitCommEvent().  This call will return immediatly
  // because our port was created as an async port (FILE_FLAG_OVERLAPPED
  // and an m_OverlappedStructerlapped structure specified).  This call will cause the
  // m_OverlappedStructerlapped element m_OverlappedStruct.hEvent, which is part of the m_hEventArray to
  // be placed in a non-signeled state if there are no bytes available to be read,
  // or to a signeled state if there are bytes available.  If this event handle
  // is set to the non-signeled state, it will be set to signeled when a
  // character arrives at the port.

  // we do this for each port!

  bResult = WaitCommEvent(port->m_hComm, &Event, &port->m_ov);

  if (!bResult) 
  {
   // If WaitCommEvent() returns FALSE, process the last error to determin
   // the reason..
   switch (dwError = GetLastError())
   {
   case ERROR_IO_PENDING:  
    {
     // This is a normal return value if there are no bytes
     // to read at the port.
     // Do nothing and continue
     break;
    }
   case 87:
    {
     // Under Windows NT, this value is returned for some reason.
     // I have not investigated why, but it is also a valid reply
     // Also do nothing and continue.
     break;
    }
   default:
    {
     // All other error codes indicate a serious error has
     // occured.  Process this error.
     port->ProcessErrorMessage("WaitCommEvent()");
     break;
    }
   }
  }
  else
  {
   // If WaitCommEvent() returns TRUE, check to be sure there are
   // actually bytes in the buffer to read. 
   //
   // If you are reading more than one byte at a time from the buffer
   // (which this program does not do) you will have the situation occur
   // where the first byte to arrive will cause the WaitForMultipleObjects()
   // function to stop waiting.  The WaitForMultipleObjects() function
   // resets the event handle in m_OverlappedStruct.hEvent to the non-signelead state
   // as it returns. 
   //
   // If in the time between the reset of this event and the call to
   // ReadFile() more bytes arrive, the m_OverlappedStruct.hEvent handle will be set again
   // to the signeled state. When the call to ReadFile() occurs, it will
   // read all of the bytes from the buffer, and the program will
   // loop back around to WaitCommEvent().
   //
   // At this point you will be in the situation where m_OverlappedStruct.hEvent is set,
   // but there are no bytes available to read.  If you proceed and call
   // ReadFile(), it will return immediatly due to the async port setup, but
   // GetOverlappedResults() will not return until the next character arrives.
   //
   // It is not desirable for the GetOverlappedResults() function to be in
   // this state.  The thread shutdown event (event 0) and the WriteFile()
   // event (Event2) will not work if the thread is blocked by GetOverlappedResults().
   //
   // The solution to this is to check the buffer with a call to ClearCommError().
   // This call will reset the event handle, and if there are no bytes to read
   // we can loop back through WaitCommEvent() again, then proceed.
   // If there are really bytes to read, do nothing and proceed.
  
   bResult = ClearCommError(port->m_hComm, &dwError, &comstat);

   if (comstat.cbInQue == 0)
    continue;
  } // end if bResult

  // Main wait function.  This function will normally block the thread
  // until one of nine events occur that require action.
  Event = WaitForMultipleObjects(3, port->m_hEventArray, FALSE, INFINITE);

  switch (Event)
  {
  case 0:
   {
    // Shutdown event.  This is event zero so it will be
    // the higest priority and be serviced first.

     port->m_bThreadAlive = FALSE;
    
    // Kill this thread.  break is not needed, but makes me feel better.
    AfxEndThread(100);
    break;
   }
  case 1: // read event
   {
    GetCommMask(port->m_hComm, &CommEvent);
    if (CommEvent & EV_CTS)
     ::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_CTS_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
    if (CommEvent & EV_RXFLAG)
     ::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_RXFLAG_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
    if (CommEvent & EV_BREAK)
     ::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_BREAK_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
    if (CommEvent & EV_ERR)
     ::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_ERR_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
    if (CommEvent & EV_RING)
     ::SendMessage(port->m_pOwner->m_hWnd, WM_COMM_RING_DETECTED, (WPARAM) 0, (LPARAM) port->m_nPortNr);
    
    if (CommEvent & EV_RXCHAR)
     // Receive character event from port.
     ReceiveChar(port, comstat);
     
    break;
   } 
  case 2: // write event
   {
    // Write character event from port
    WriteChar(port);
    break;
   }

  } // end switch

 } // close forever loop

 return 0;
}