MFC串口编程——使用标准SerialCom类

附件为实现visual studio C++串口通讯的类

使用方法，定义一个类：CSerialCom m_serialCom;

然后使用

m_serialCom.InitPort(this, nPort, nBaud, 'E');
m_serialCom.StartMonitoring();

开始监控报文

 

使用

m_serialCom.ClosePort();

关闭串口

 

同时需要定义一个串口数据消息回调接收函数

ON_MESSAGE(WM_COMM_RXCHAR, &OnReceiveData)

LRESULT CVS_CCO_FOR_UpgradeDlg::OnReceiveData(WPARAM wParam, LPARAM lParam)
{
    Uart_Has_RecOneByte = TRUE;
    uart_time_count = 0;
    ringq_push(&ringq_rbuff, (BYTE)wParam);
    
    return 0;
}

 

 

 

附件：SerialCom.cpp

#include "stdafx.h"
#include "SerialCom.h"
#include <assert.h>
//
// Constructor
//
#pragma warning(disable:4996)
CSerialCom::CSerialCom()
{
    m_hComm = NULL;
    // initialize overlapped structure members to zero
    m_ov.Offset = 0;
    m_ov.OffsetHigh = 0;
    // create events
    m_ov.hEvent = NULL;
    m_hWriteEvent = NULL;
    m_hShutdownEvent = NULL;
    m_szWriteBuffer = NULL;
    m_nWriteSize = 1;
    m_bThreadAlive = FALSE;
}
//
// Delete dynamic memory
//
CSerialCom::~CSerialCom()
{
    do
    {
        SetEvent(m_hShutdownEvent);
    } while (m_bThreadAlive);

    TRACE("Thread ended/n");
    delete[] m_szWriteBuffer;
}
//
// Initialize the port. This can be port 1 to 4.
//
BOOL CSerialCom::InitPort(CWnd* pPortOwner, // the owner (CWnd) of the port (receives message)
    UINT  portnr,  // portnumber (1..8)
    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 < 20);
    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);
    m_ov.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
    if (m_hWriteEvent != NULL)
        ResetEvent(m_hWriteEvent);
    m_hWriteEvent = CreateEvent(NULL, TRUE, FALSE, NULL);

    if (m_hShutdownEvent != NULL)
        ResetEvent(m_hShutdownEvent);
    m_hShutdownEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
    // initialize the event objects
    m_hEventArray[0] = m_hShutdownEvent; // highest priority
    m_hEventArray[1] = m_hWriteEvent;
    m_hEventArray[2] = m_ov.hEvent;
    // 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 = CreateFileA(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.EvtChar = 'q';
                m_dcb.fRtsControl = RTS_CONTROL_ENABLE;  // set RTS bit high!
                if (BuildCommDCBA(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;
}
//
//  The CommThread Function.
//
UINT CSerialCom::CommThread(LPVOID pParam)
{
    // Cast the void pointer passed to the thread back to
    // a pointer of CSerialCom class
    CSerialCom *port = (CSerialCom*)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;
    memset(&comstat, 0, sizeof(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.
            CloseHandle(port->m_hComm);
            port->m_hComm = NULL;
            port->m_bThreadAlive = FALSE;

            // Kill this thread.  break is not needed, but makes me feel better.
            AfxEndThread(100);
            break;
        }
        case 2: // 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 1: // write event
        {
            // Write character event from port
            WriteChar(port);
            break;
        }
        } // end switch
    } // close forever loop
    return 0;
}
//
// start comm watching
//
BOOL CSerialCom::StartMonitoring()
{
    if (!(m_Thread = AfxBeginThread(CommThread, this)))
        return FALSE;
    TRACE("Thread started/n");
    return TRUE;
}
//
// Restart the comm thread
//
BOOL CSerialCom::RestartMonitoring()
{
    TRACE("Thread resumed/n");
    m_Thread->ResumeThread();
    return TRUE;
}

//
// Suspend the comm thread
//
BOOL CSerialCom::StopMonitoring()
{
    TRACE("Thread suspended/n");
    m_Thread->SuspendThread();
    return TRUE;
}

//
// If there is a error, give the right message
//
void CSerialCom::ProcessErrorMessage(char* ErrorText)
{
    char *Temp = new char[200];

    LPVOID lpMsgBuf;
    FormatMessage(
        FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
        NULL,
        GetLastError(),
        MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), // Default language
        (LPTSTR)&lpMsgBuf,
        0,
        NULL
        );
    sprintf(Temp, "WARNING:  %s Failed with the following error: /n%s/nPort: %d/n", ErrorText, (char*)lpMsgBuf, m_nPortNr);
    MessageBoxA(NULL, Temp, "Application Error", MB_ICONSTOP);
    LocalFree(lpMsgBuf);
    delete[] Temp;
}
//
// Write a character.
//
void CSerialCom::WriteChar(CSerialCom* port)
{
    BOOL bWrite = TRUE;
    BOOL bResult = TRUE;
    DWORD BytesSent = 0;
    ResetEvent(port->m_hWriteEvent);
    // Gain ownership of the critical section
    EnterCriticalSection(&port->m_csCommunicationSync);
    if (bWrite)
    {
        // Initailize variables
        port->m_ov.Offset = 0;
        port->m_ov.OffsetHigh = 0;
        // Clear buffer
        PurgeComm(port->m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT);
        bResult = WriteFile(port->m_hComm,       // Handle to COMM Port
            port->m_szWriteBuffer,     // Pointer to message buffer in calling finction
                                       //       strlen((char*)port->m_szWriteBuffer), // Length of message to send
            port->m_nWriteSize, // Length of message to send
            &BytesSent,        // Where to store the number of bytes sent
            &port->m_ov);       // Overlapped structure
                                // deal with any error codes
        if (!bResult)
        {
            DWORD dwError = GetLastError();
            switch (dwError)
            {
            case ERROR_IO_PENDING:
            {
                // continue to GetOverlappedResults()
                BytesSent = 0;
                bWrite = FALSE;
                break;
            }
            default:
            {
                // all other error codes
                port->ProcessErrorMessage("WriteFile()");
            }
            }
        }
        else
        {
            LeaveCriticalSection(&port->m_csCommunicationSync);
        }
    } // end if(bWrite)
    if (!bWrite)
    {
        bWrite = TRUE;

        bResult = GetOverlappedResult(port->m_hComm, // Handle to COMM port 
            &port->m_ov,  // Overlapped structure
            &BytesSent,  // Stores number of bytes sent
            TRUE);    // Wait flag
        LeaveCriticalSection(&port->m_csCommunicationSync);
        // deal with the error code 
        //  if (!bResult)  
        {
            //   port->ProcessErrorMessage("GetOverlappedResults() in WriteFile()");
        }
    } // end if (!bWrite)
      // Verify that the data size send equals what we tried to send
      // if (BytesSent != strlen((char*)port->m_szWriteBuffer))
    {
        //  TRACE("WARNING: WriteFile() error.. Bytes Sent: %d; Message Length: %d/n", BytesSent, strlen((char*)port->m_szWriteBuffer));
    }
    // ::SendMessage((port->m_pOwner)->m_hWnd, WM_COMM_TXEMPTY_DETECTED, (WPARAM) RXBuff, (LPARAM) port->m_nPortNr);
    ::SendMessage((port->m_pOwner)->m_hWnd, WM_COMM_TXEMPTY_DETECTED, 0, (LPARAM)port->m_nPortNr);
}
//
// Character received. Inform the owner
//
void CSerialCom::ReceiveChar(CSerialCom* port, COMSTAT comstat)
{
    BOOL  bRead = TRUE;
    BOOL  bResult = TRUE;
    DWORD dwError = 0;
    DWORD BytesRead = 0;
    unsigned char RXBuff;
    for (;;)
    {
        // Gain ownership of the comm port critical section.
        // This process guarantees no other part of this program 
        // is using the port object. 

        EnterCriticalSection(&port->m_csCommunicationSync);
        // ClearCommError() will update the COMSTAT structure and
        // clear any other errors.

        bResult = ClearCommError(port->m_hComm, &dwError, &comstat);
        LeaveCriticalSection(&port->m_csCommunicationSync);
        // start forever loop.  I use this type of loop because I
        // do not know at runtime how many loops this will have to
        // run. My solution is to start a forever loop and to
        // break out of it when I have processed all of the
        // data available.  Be careful with this approach and
        // be sure your loop will exit.
        // My reasons for this are not as clear in this sample 
        // as it is in my production code, but I have found this 
        // solutiion to be the most efficient way to do this.

        if (comstat.cbInQue == 0)
        {
            // break out when all bytes have been read
            break;
        }

        EnterCriticalSection(&port->m_csCommunicationSync);
        if (bRead)
        {
            bResult = ReadFile(port->m_hComm,  // Handle to COMM port 
                &RXBuff,    // RX Buffer Pointer
                1,     // Read one byte
                &BytesRead,   // Stores number of bytes read
                &port->m_ov);  // pointer to the m_ov structure
                               // deal with the error code 
            if (!bResult)
            {
                switch (dwError = GetLastError())
                {
                case ERROR_IO_PENDING:
                {
                    // asynchronous i/o is still in progress 
                    // Proceed on to GetOverlappedResults();
                    bRead = FALSE;
                    break;
                }
                default:
                {
                    // Another error has occured.  Process this error.
                    port->ProcessErrorMessage("ReadFile()");
                    break;
                }
                }
            }
            else
            {
                // ReadFile() returned complete. It is not necessary to call GetOverlappedResults()
                bRead = TRUE;
            }
        }  // close if (bRead)
        if (!bRead)
        {
            bRead = TRUE;
            bResult = GetOverlappedResult(port->m_hComm, // Handle to COMM port 
                &port->m_ov,  // Overlapped structure
                &BytesRead,  // Stores number of bytes read
                TRUE);    // Wait flag
                          // deal with the error code 
            if (!bResult)
            {
                port->ProcessErrorMessage("GetOverlappedResults() in ReadFile()");
            }
        }  // close if (!bRead)

        LeaveCriticalSection(&port->m_csCommunicationSync);
        // notify parent that a byte was received
        ::SendMessage((port->m_pOwner)->m_hWnd, WM_COMM_RXCHAR, (WPARAM)RXBuff, (LPARAM)port->m_nPortNr);//发送消息，对应的消息函数接收数据
    } // end forever loop
}
//
// Write a string to the port
//
void CSerialCom::WriteToPort(char* string)
{
    assert(m_hComm != 0);

    memset(m_szWriteBuffer, 0, sizeof(m_szWriteBuffer));
    strcpy(m_szWriteBuffer, string);
    m_nWriteSize = strlen(string);
    // set event for write
    SetEvent(m_hWriteEvent);
}

void CSerialCom::WriteToPort(char* string, int n)
{
    assert(m_hComm != 0);
    memset(m_szWriteBuffer, 0, sizeof(m_szWriteBuffer));
    // memset(m_szWriteBuffer, 0, n);
    // strncpy(m_szWriteBuffer, string, n);
    memcpy(m_szWriteBuffer, string, n);
    m_nWriteSize = n;
    // set event for write
    SetEvent(m_hWriteEvent);
}


#if 0
void CSerialCom::WriteToPort(LPCTSTR string)
{
    assert(m_hComm != 0);
    memset(m_szWriteBuffer, 0, sizeof(m_szWriteBuffer));
    strcpy(m_szWriteBuffer, string);
    m_nWriteSize = strlen(string);
    // set event for write
    SetEvent(m_hWriteEvent);
}
#endif
void CSerialCom::WriteToPort(LPCTSTR string, int n)
{
    assert(m_hComm != 0);
    memset(m_szWriteBuffer, 0, sizeof(m_szWriteBuffer));
    // strncpy(m_szWriteBuffer, string, n);
    memcpy(m_szWriteBuffer, string, n);
    m_nWriteSize = n;
    // set event for write
    SetEvent(m_hWriteEvent);
}
//
// Return the device control block
//
DCB CSerialCom::GetDCB()
{
    return m_dcb;
}
//
// Return the communication event masks
//
DWORD CSerialCom::GetCommEvents()
{
    return m_dwCommEvents;
}
//
// Return the output buffer size
//
DWORD CSerialCom::GetWriteBufferSize()
{
    return m_nWriteBufferSize;
}

void CSerialCom::ClosePort()
{
    SetEvent(m_hShutdownEvent);
}

void CSerialCom::EnumerateSerialPorts(CUIntArray& ports)
{
    ports.RemoveAll();    //Make sure we clear out any elements which may already be in the array

                        //Determine what OS we are running on
    OSVERSIONINFO osvi;
    osvi.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);
    BOOL bGetVer = GetVersionEx(&osvi);

    //On NT use the QueryDosDevice API
    if (bGetVer && (osvi.dwPlatformId == VER_PLATFORM_WIN32_NT))
    {
        //Use QueryDosDevice to look for all devices of the form COMx. This is a better
        //solution as it means that no ports have to be opened at all.
        TCHAR szDevices[65535];
        DWORD dwChars = QueryDosDevice(NULL, szDevices, 65535);
        if (dwChars) {
            int i = 0;
            for (;;) {
                TCHAR* pszCurrentDevice = &szDevices[i];    //Add the port number to the array which will be returned
                                                            //If it looks like "COMX" then
                                                            //add it to the array which will be returned
                int nLen = _tcslen(pszCurrentDevice);
                if (nLen > 3 && _tcsnicmp(pszCurrentDevice, _T("COM"), 3) == 0) {
                    int nPort = _ttoi(&pszCurrentDevice[3]);    //Work out the port number
                    ports.Add(nPort);        //clear out com_0
                }
                // Go to next NULL character
                while (szDevices[i] != _T('\0')) i++;
                i++;    // Bump pointer to the next string
                        // The list is double-NULL terminated, so if the character is
                        // now NULL, we're at the end
                if (szDevices[i] == _T('\0')) break;
            }
        }
        else TRACE(_T("Failed in call to QueryDosDevice, GetLastError:%d\n"), GetLastError());
    }
    else {
        //On 95/98 open up each port to determine their existence
        //Up to 255 COM ports are supported so we iterate through all of them seeing
        //if we can open them or if we fail to open them, get an access denied or general error error.
        //Both of these cases indicate that there is a COM port at that number. 
        for (UINT i = 1; i<256; i++)
        {
            //Form the Raw device name
            CString sPort;
            sPort.Format(_T("\\\\.\\COM%d"), i);

            //Try to open the port
            BOOL bSuccess = FALSE;
            HANDLE hPort = ::CreateFile(sPort, GENERIC_READ | GENERIC_WRITE, 0, 0, OPEN_EXISTING, 0, 0);
            if (hPort == INVALID_HANDLE_VALUE)
            {
                DWORD dwError = GetLastError();
                //Check to see if the error was because some other app had the port open or a general failure
                if (dwError == ERROR_ACCESS_DENIED || dwError == ERROR_GEN_FAILURE)
                    bSuccess = TRUE;
            }
            else {
                bSuccess = TRUE;    //The port was opened successfully                
                CloseHandle(hPort);    //Don't forget to close the port, since we are going to do nothing with it anyway
            }
            if (bSuccess) ports.Add(i);    //Add the port number to the array which will be returned
        }
    }
}

 

SerialCom.h

#pragma once

#define WM_COMM_BREAK_DETECTED  WM_USER+1 // A break was detected on input.
#define WM_COMM_CTS_DETECTED  WM_USER+2 // The CTS (clear-to-send) signal changed state. 
#define WM_COMM_DSR_DETECTED  WM_USER+3 // The DSR (data-set-ready) signal changed state. 
#define WM_COMM_ERR_DETECTED  WM_USER+4 // A line-status error occurred. Line-status errors are CE_FRAME, CE_OVERRUN, and CE_RXPARITY. 
#define WM_COMM_RING_DETECTED  WM_USER+5 // A ring indicator was detected. 
#define WM_COMM_RLSD_DETECTED  WM_USER+6 // The RLSD (receive-line-signal-detect) signal changed state. 
#define WM_COMM_RXCHAR    WM_USER+7 // A character was received and placed in the input buffer. 
#define WM_COMM_RXFLAG_DETECTED  WM_USER+8 // The event character was received and placed in the input buffer.  
#define WM_COMM_TXEMPTY_DETECTED WM_USER+9 // The last character in the output buffer was sent. 
class CSerialCom
{
public:
    int m_nWriteSize;
    void ClosePort();
    // contruction and destruction
    CSerialCom();
    virtual  ~CSerialCom();
    // port initialisation           
    BOOL  InitPort(CWnd* pPortOwner, UINT portnr = 1, UINT baud = 9600, char parity = 'N', UINT databits = 8, UINT stopbits = 1, DWORD dwCommEvents = EV_RXCHAR, UINT writebuffersize = 1024);
    HANDLE    m_hComm;
    // start/stop comm watching
    BOOL  StartMonitoring();
    BOOL  RestartMonitoring();
    BOOL  StopMonitoring();
    DWORD  GetWriteBufferSize();
    DWORD  GetCommEvents();
    DCB   GetDCB();
    void  WriteToPort(char* string);
    void  WriteToPort(char* string, int n);
    void  WriteToPort(LPCTSTR string);
    void  WriteToPort(LPCTSTR string, int n);
    void EnumerateSerialPorts(CUIntArray& ports);
protected:
    // protected memberfunctions
    void  ProcessErrorMessage(char* ErrorText);
    static UINT CommThread(LPVOID pParam);
    static void ReceiveChar(CSerialCom* port, COMSTAT comstat);
    static void WriteChar(CSerialCom* port);
    // thread
    CWinThread*   m_Thread;
    // synchronisation objects
    CRITICAL_SECTION m_csCommunicationSync;
    BOOL    m_bThreadAlive;
    // handles
    HANDLE    m_hWriteEvent;
    HANDLE    m_hShutdownEvent;
    // Event array. 
    // One element is used for each event. There are two event handles for each port.
    // A Write event and a receive character event which is located in the overlapped structure (m_ov.hEvent).
    // There is a general shutdown when the port is closed. 
    HANDLE    m_hEventArray[3];
    // structures
    OVERLAPPED   m_ov;
    COMMTIMEOUTS  m_CommTimeouts;
    DCB     m_dcb;
    // owner window
    CWnd*    m_pOwner;
    // misc
    UINT    m_nPortNr;
    char*    m_szWriteBuffer;
    DWORD    m_dwCommEvents;
    DWORD    m_nWriteBufferSize;    
};