串口程序中函数使用WaitCommEvent、ClearCommError、GetcommMask

在串口程序中的几个函数的联合使用
一、首先是利用WaitCommEvent
来等待串口事件的被触发，这些事件是指在该函数被调用前，我们自己设置好的能触发串口线程的有效事件。
主要包括3类事件：
  1.
函数SetCommMask (ceSeries->m_hComm, EV_RXCHAR |EV_CTS | EV_DSR )设置的数据接收中断
  2.用户中断线程的操作。
  3.
用户发送数据所产生的中断。
该函数相当于利用事件来同步，实际函数也是这么设计的。但没有有效中断触发，线程会一直在这里等待。
一旦被触发，程序才能继续往下执行。
 
二、函数WaitCommEvent执行完成后，他的返回值若为零，说明有错误，这时候用GetLastError来查询错误类型。
 
三、函数WaitCommEvent执行返回值若为1，则用ClearCommError来清除错误，并查询串口的状态，得到comstat的值。
 
四、检查ClearCommError所查询的串口状态comstat.cbInQue的值，若不大于0，说明错误。继续等待事件的触发
 
五、若omstat.cbInQue大于0，说明buffer里面有字符。在使用WaitForMultipleObjects函数确认事件，并执行对应的操作。
 
//WaitCommEvent函数为指定的通信资源监听一系列的Event,这些Event可以由
SetcommMask和 GetcommMask函数来设置和查询。
 
 
例子：
 
bResult =WaitCommEvent(port->m_hComm, &Event, &port->m_ov);

        if (!bResult)  

        { 

            // If WaitCommEvent() returns FALSE,process
the last error to determin

            switch (dwError =GetLastError()) 

            { 

            case ERROR_IO_PENDING:    

                { 

                    break;

                }

            case 87:

                {

                    break;

                }

            default:

                {

                    port->ProcessErrorMessage("WaitCommEvent()");

                    break;

                }

            }

        }

        else

        {

         

            bResult =ClearCommError(port->m_hComm,
&dwError, &comstat);

            if (comstat.cbInQue == 0)

                continue;

        }    // end if bResult

            //m_hEventArray[0] =m_hShutdownEvent;    //
highest priority

            //m_hEventArray[1] = m_ov.hEvent;

            //m_hEventArray[2] = m_hWriteEvent;

        Event = WaitForMultipleObjects(3,port->m_hEventArray, FALSE, INFINITE);

        switch (Event)

        {

        case 0:

            {

                //
Shutdown event.  This is event zero so it will be// thehigest priority and be serviced first.                

                CloseHandle(port->m_hComm);

                port->m_hComm=NULL;

                port->m_bThreadAlive
=FALSE;                

                //
Kill this thread.  break is not needed, but makes me feelbetter.

                AfxEndThread(100);

                break;

            }

        case 1:    // read event

            {

                GetCommMask(port->m_hComm,&CommEvent);

                if
(CommEvent & EV_RXCHAR)

                    //
Receive character event from port.

                    ReceiveChar(port,
comstat);

                if
(CommEvent & EV_CTS)

                    ::SendMessage(port->m_pOwner->m_hWnd,WM_COMM_CTS_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_RXFLAG)

                    ::SendMessage(port->m_pOwner->m_hWnd,WM_COMM_RXFLAG_DETECTED,
(WPARAM) 0, (LPARAM) port->m_nPortNr);

                    

                break;

            }  

        case 2: // write event

            {

                //
Write character event from port

                WriteChar(port);

                break;

            }

        } // end switch

    } // closeforever loop