如何去掉阻塞在串口上的读操作？

2008-11-21 01:46:45 223 阅读 AI 写同款 · GEO 优化AI 选题数据监测一键分发 ›

串口阻塞和非阻塞阻塞方式是文件读写操作的默认方式，但是应用程序员可通过使用O_NONBLOCK 标志来人为的设置读写操作为非阻塞方式 .( 该标志定义在 &lt; linux/fcntl.h &gt; 中，在打开文件时指定 ) . 阻塞：在设计简单字符驱动程序时，要注意一个重要问题. 当一个设备无法立刻满足用户的读写请求时应当如何处理? ... 阅读详情

串口的打开方式：（非重叠方式打开）
hPort = CreateFile ("COM1", GENERIC_READ|GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL);

SetCommMask (hPort, EV_RXCHAR); //事件,读

程序然后阻塞在这里（位于启动的一个线程里头）：
WaitCommEvent(hPort, &commStatus, 0);等待串口上的写数据发生，以便在程序中读取。

问题就是现在欲关闭串口的线程，程序却一直仍阻塞在这里。

...全文

linux串口编程--规范模式和非规范模式及read的阻塞与非阻塞 1.阻塞与非阻塞1.1 阻塞的定义对于read，指当串口输入缓存区没有数据的时候，read函数将会阻塞在这里，直到串口输入缓存区中有数据可读取，read读到了需要的字节数之后，返回值为读到的字节数；对于write，指当串口输出缓冲区满，或剩下的空间小于将要写入的字节数，则write将阻塞，一直到串口输出缓冲区中剩下的空间大于等于将要写入的字节数，执行写入操作，返回写入的字节数。1.2 非阻塞的定义... 阅读详情

山的那边还是山~

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切换为时间正序

rookieme 2008-11-22

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OVERLAPPED方式在EVC中是不支持滴！
如果是在VC中可以

ilovedrv 2008-11-22

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如果坚持用这种阻塞方式，那就没办法了，只能用最极端的方法，调用TerminateThread终止线程

建议还是用异步方式读取数据,OVERLAPPED方式

schlafenhamster 2008-11-22

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用异步读:
//1>. an work thread to monitor the _CTS and RX_CHAR //可以去_CTS
UINT CUload::CommWatchRead(LPVOID lpParam)
{ // return 0=OK 1=Error
CUload *pUload=(CUload*)lpParam;
OVERLAPPED os;
DWORD dwEventMask,dwTransfer;

memset(&os,0,sizeof(OVERLAPPED));
os.hEvent=CreateEvent(NULL,TRUE,FALSE,NULL);// attrb,Manual,init,name
if (os.hEvent==NULL)
{
AfxMessageBox("Can't create Event",MB_ICONSTOP);
return 1;// error
}
// set 2 events !
if (!SetCommMask(pUload->m_idComDev,EV_RXCHAR|EV_CTS)) return 1;
while (pUload->m_bConnected)
{ // break,only if m_bConnected=NULL

dwEventMask=0;
if(!WaitCommEvent(pUload->m_idComDev,&dwEventMask,&os))
{ // function fails
if (GetLastError()==ERROR_IO_PENDING)
{// TRUE=WaitForSingleObject() should be called inside
GetOverlappedResult(pUload->m_idComDev,&os,&dwTransfer,TRUE);
os.Offset+=dwTransfer;
}
}
if((dwEventMask & EV_RXCHAR)==EV_RXCHAR)
{ // some chats received.
ResetEvent(pUload->m_hPostEventRead);// first reset
pUload->PostMessage(WM_COMMNOTIFY,
(WPARAM)1, // EV_RXCHAR
(LPARAM)0); // not used
// wait answer
WaitForSingleObject(pUload->m_hPostEventRead,0xFFFFFFFF);
}
// if not at same time,use else if
if((dwEventMask & EV_CTS)==EV_CTS)
{ // CTS changed
ResetEvent(pUload->m_hPostEventRead);// first reset
pUload->PostMessage(WM_COMMNOTIFY,
(WPARAM)0, // EV_CTS
(LPARAM)0); // not used
// wait answer
WaitForSingleObject(pUload->m_hPostEventRead,0xFFFFFFFF);
}
}
CloseHandle(os.hEvent);
return 0;// OK
}
//2>.一个消息
// use ON_MESSAGE(a,b)
void CUload::OnCommNotify(WPARAM wParam,LPARAM lParam)
{
// TODO: Add your specialized code here and/or call the base class
int nLength;
BYTE abIn[6000];// for 115200 needs 4096 and more
DWORD totalrecv;
CString txt;
switch(wParam)
{
case 0:// from CommWatchCTS()
SetCTSIcon();
SetEvent(m_hPostEventRead);// tell watcher that CommNotify has been done
break;
case 1:// from CommWatchRead()
// append on each entry
CFile uldFile(UpLoadFileName,CFile::modeCreate|CFile::modeNoTruncate|CFile::modeWrite);
uldFile.SeekToEnd( );
if (m_bConnected)
{
if(nLength=ReadCommBlock(abIn,BUFLEN))// 38400 needs 1024
{ // save into file
if (!m_bStart)
{ // only 1st
m_bStart=1;
InforOut("Receiving "+UpLoadFileName);
}
uldFile.Write(abIn,nLength);
}
}
uldFile.Close();
// get total bytes received
m_uldINs.GetText(0,txt);
totalrecv=atol(txt.GetBuffer(40));
totalrecv+=nLength;
txt.Format("%d",totalrecv);
m_uldINs.ResetContent();
m_uldINs.AddString(txt);
if (nLength>128)
{
Animate();
// reset "time waiting"
m_Elapse.ResetContent();
m_Elapse.AddString("0 s");
}
// tell watcher that CommNotify has been done
SetEvent(m_hPostEventRead);
break;
}
}
//3>.实际读
int CUload::ReadCommBlock(BYTE *pBlock,int nBlockLen)
{ //return 0 if error
int WaitErr;
BOOL fReadStart;
COMSTAT ComStat;
DWORD dwErrorFlags,dwLength;

if (!m_bConnected) return 0;

if (ClearCommError(m_idComDev,&dwErrorFlags,&ComStat))
{ //ComStat filled
if (dwErrorFlags)
{
if (dwErrorFlags & CE_RXOVER) AfxMessageBox("Receive Queue overflow");
else if(dwErrorFlags & CE_OVERRUN) AfxMessageBox("Receive Overrun Error");
else if(dwErrorFlags & CE_RXPARITY) AfxMessageBox("Receive Parity Error");
else if(dwErrorFlags & CE_FRAME ) AfxMessageBox("Receive Framing error");
else if(dwErrorFlags & CE_BREAK) AfxMessageBox("Break Detected");
else AfxMessageBox("CE_OTHERS");
}
}
// nBlockLen may >,=,< ComStat.cbInQue !
dwLength=min((DWORD)nBlockLen,ComStat.cbInQue);
if(dwLength>0)
{ // read required
fReadStart=ReadFile(m_idComDev,pBlock,dwLength,&dwLength,&m_osRead);
if(!fReadStart)
{ // if there was a problem, or the async. operation's still pending ...
if(GetLastError()==ERROR_IO_PENDING)
{ // asynchronous i/o is still in progress
if (WaitErr=WaitForSingleObject(m_osRead.hEvent,60000))// 1 minute
{ // time over
if(WaitErr==WAIT_TIMEOUT)
{ // time out
dwLength=0;
AfxMessageBox("Time out !");
}// end time out
}// end waiterr
} // end io_pending
else
{ // WaitErr=0.if you SetEvent(m_osRead.hEvent) anywhere else
GetOverlappedResult(m_idComDev,&m_osRead,&dwLength,FALSE);
m_osRead.Offset +=dwLength;
}
}
} //end if dwLength>0
return dwLength;
}
//4.线程退出
置m_bConnected=FALSE
m_bConnected必须是volatile的

dirdirdir3 2008-11-21

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既然需要关闭，使用overlapped比较方便.........

gamezealot 2008-11-21

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同意楼上的，很久以前做过，就是用OVERLAPPED方式做的。你可以参考下MSDN，WaitCommEvent这个函数的说明下面有个例子叫做：
see Monitoring Communications Events.

whatabig 2008-11-21

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in your main thread,
WriteFile(hPort,"close port cmd")
thus release
WaitCommEvent(hPort, &commStatus, 0);

while(!isclose)
{
WaitCommEvent(hPort, &commStatus, 0);
ReadFile(hPort, pbuf,len);
if(pbuf=="close port comd")
isclose=false;
}

cleanup routine

zaodt 2008-11-21

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楼主，你还是考虑重叠方式吧。

如何去掉阻塞在串口上的读操作？

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