PC通过串口读取rs232条码扫描枪扫描的条码有关问题

UINT __cdecl OnWatchCom(LPVOID lparam)
{
    CBillDlg *pDlg = (CBillDlg *)lparam;
    if(pDlg == NULL) return -1;
    CString strResult;
    char buff[128] = {0};
    while(pDlg->m_IsWatching)
    {
        if(pDlg->m_Com.ReadCom(buff,128,2000))
        {
            pDlg->m_Com.ClearComBuf(PURGE_TXABORT | PURGE_RXABORT | PURGE_TXCLEAR | PURGE_RXCLEAR);
            strResult.Format(_T("%s"),buff);
            if(!strResult.IsEmpty())
            {
                pDlg->m_strBillNo = strResult;
                pDlg->UpdateData(0);        
            }
        }
        Sleep(50);
    }
    return 0;
}
BOOL CComport::ReadCom(char *buff, int nlen, int dwMiniTimeout)
{
    if(!IsOpen()) return FALSE;
    OVERLAPPED m_osRead;
    memset(&m_osRead,0,sizeof(OVERLAPPED));
    m_osRead.hEvent=CreateEvent(NULL,TRUE,FALSE,NULL);

    COMSTAT ComStat;
    DWORD dwErrorFlags;
    
    memset(buff,'\0',nlen);
    DWORD dwBytesRead=nlen;//读取的字节数
    BOOL bReadStat;

    ClearComErr(&dwErrorFlags,&ComStat);
    dwBytesRead=min(dwBytesRead, (DWORD)ComStat.cbInQue);
    bReadStat=ReadFile(m_hCom,buff,dwBytesRead,&dwBytesRead,&m_osRead);
    if(!bReadStat)
    {
        if(GetLastError()==ERROR_IO_PENDING)//GetLastError()函数返回ERROR_IO_PENDING,表明串口正在进行读操作
        {
            //GetOverlappedResult(m_hCom,&m_osRead,&dwBytesRead,TRUE);
            WaitForSingleObject(m_osRead.hEvent,dwMiniTimeout);
            //使用WaitForSingleObject函数等待，直到读操作完成或延时已达到2秒钟
            //当串口读操作进行完毕后，m_osRead的hEvent事件会变为有信号
            //ResetEvent(m_osRead.hEvent);
        }
    }
    CloseHandle(m_osRead.hEvent);
    return TRUE;
}