求用定时器定时读串口的方法

BOOL CTestCommandDlg::InitPort(CString strPortName)
{//创建串口句柄对象，重叠IO操作。
g_hCom=::CreateFile(strPortName,GENERIC_READ|GENERIC_WRITE,0,NULL,OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL|FILE_FLAG_OVERLAPPED,NULL);
if(INVALID_HANDLE_VALUE==g_hCom)
{ ::CloseHandle(g_hCom);
return false;
}
//设置串口缓冲大小
if(!::SetupComm(g_hCom,BUFFERSIZE,BUFFERSIZE))//BUFFERSIZE=1024;
return false;
//设置串口事件
if(!::SetCommMask(g_hCom,EV_RXCHAR))
return false;
//得到上一次串口状态
if(!::GetCommState(g_hCom,&g_dcbCom))
return false;
//修改DCB
g_dcbCom.fParity=1;
g_dcbCom.BaudRate=9600;//波特率
g_dcbCom.ByteSize=8;//数据位
g_dcbCom.StopBits=ONESTOPBIT;//停止位
g_dcbCom.Parity=NOPARITY;//校验位
//配置串口
if(!::SetCommState(g_hCom,&g_dcbCom))
return false;
//设置超时
memset(&g_ComTimeOuts,0,sizeof(g_ComTimeOuts));
g_ComTimeOuts.ReadIntervalTimeout=1000; //具体时间根据实际情况决定
g_ComTimeOuts.ReadTotalTimeoutMultiplier=50; //
g_ComTimeOuts.ReadTotalTimeoutConstant=500; //
g_ComTimeOuts.WriteTotalTimeoutMultiplier=500;//
g_ComTimeOuts.WriteTotalTimeoutConstant=1000; //
if(!::SetCommTimeouts(g_hCom,&g_ComTimeOuts))
return false;
//清空端口
::PurgeComm(g_hCom,PURGE_TXCLEAR|PURGE_RXCLEAR|PURGE_TXABORT|PURGE_RXABORT);
return true;
}

//设置定时器，定时时间1000ms
SetTimer(0x0001,1000,NULL);
//处理定时器消息函数(OnTimer())里调用读串口数据
ReadData(handle,szReadBuffer,dwLength);

//
//读串口数据
//
BOOL ReadData(HANDLE handle,char *szReadBuffer,DWORD dwLength)
{
if(!IsOpen())//判断串口句柄不为空，可以省略。
return false;
DWORD dwReadBytes;//实际读到字节数
BOOL bResult;//读操作返回值
DWORD dwError;//错误标志
COMSTAT Stat;memset(&Stat,0,sizeof(Stat));
//通过清除串口错误和串口当前状态函数，获得串口当前数据长度
if(::ClearCommError(handle,&dwError,&Stat) && dwError>0)
{
::PurgeComm(handle,PURGE_RXCLEAR|PURGE_RXABORT);
return false;
}
if(!Stat.cbInQue)
return false;
dwLength=min(dwLength,Stat.cbInQue);
//重叠读操作
bResult=::ReadFile(handle,szReadBuffer,dwLength,&dwReadBytes,&ReadOverlapped);if(!bResult){
if(::GetLastError()==ERROR_IO_PENDING)
{
//等待串口事件发生
WaitForSingleObject(ReadOverlapped.hEvent,1000);
bResult=::GetOverlappedResult(handle,&ReadOverlapped,&dwReadBytes,true);//获得重叠读数据结果
if(!bResult)
{
dwError=GetLastError();
if(dwError!=ERROR_IO_INCOMPLETE)
return false;
}
}else
{
return false;
}
}
return true;
}

memset(&ReadOverlapped,0,sizeof(ReadOverlapped));//读重叠IO结构
memset(&WriteOverlapped,0,sizeof(WriteOverlapped));//写重叠IO结构
ReadOverlapped.hEvent=::CreateEvent(NULL,true,false,NULL);
ASSERT(ReadOverlapped.hEvent!=INVALID_HANDLE_VALUE);
WriteOverlapped.hEvent=::CreateEvent(NULL,true,false,NULL);
ASSERT(WriteOverlapped.hEvent!=INVALID_HANDLE_VALUE);