求助！关于串口的问题

[ybdfeb]

如下：
if (!WaitCommEvent(m_hCom, &dwMask, &os))
{
if (ERROR_IO_PENDING == GetLastError())
{
GetOverlappedResult(m_hCom, &os, &dwBytesRead, TRUE);
}
}

跟踪到GetOverlappedResult时程序就在这个函数里面转不出来，请问是何原因?

谢谢！

[曾经的猎狐]

GetOverlappedResult(m_hCom, &os, &dwBytesRead, FALSE); //最后一个参数设置为FALSE

[yyz2000]

关注

[QunKangLi]

GetOverlappedResult(m_hCom, &os, &dwBytesRead, FALSE);

最后一参数为TRUE时会一直等待直到操作完成。
为FALSE时，如操作完成，返回TRUE；如失败可未完成，返回FALSE，
可据GetLastError()==ERROR_IO_INCOMPLETE来分辨

[fzd999]

BOOL GetOverlappedResult(
HANDLE hFile, // handle to file, pipe, or device
LPOVERLAPPED lpOverlapped, // overlapped structure
LPDWORD lpNumberOfBytesTransferred, // bytes transferred
BOOL bWait // wait option
);

的确是最后一个参数的问题

[vcar]

异步。。。。。阻塞。。。。。

[ybdfeb]

这个函数没有超时返回这一说吗？

[DotLSong]

DWORD CLSComm::ReceiveChar(CLSComm* port, COMSTAT comstat)
{
BOOL bRead = true;
BOOL bResult = true;
DWORD dwError = 0;
DWORD dwBytes = 0;
unsigned char RXBuff;

while (1)
{
EnterCriticalSection(&port->m_csCommunicationSync);
ClearCommError(port->m_hComm, &dwError, &comstat);
LeaveCriticalSection(&port->m_csCommunicationSync);

if (comstat.cbInQue == 0)
break;

EnterCriticalSection(&port->m_csCommunicationSync);
{
if (!ReadFile(port->m_hComm, &RXBuff, 1, &dwBytes, &port->m_ov))
{
if (GetLastError() == ERROR_IO_PENDING)
GetOverlappedResult(port->m_hComm, &port->m_ov, &dwBytes, true);
}
}
LeaveCriticalSection(&port->m_csCommunicationSync);

::SendMessage(port->m_hWnd, WM_COMM_RXCHAR, (WPARAM)RXBuff, (LPARAM) port->m_uPort);
}

return dwBytes;
}

[DotLSong]

超时是通过 COMMTIMEOUTS 结构设置的

COMMTIMEOUTS m_CommTimeouts;

m_CommTimeouts.ReadIntervalTimeout = 500;
m_CommTimeouts.ReadTotalTimeoutMultiplier = 500;
m_CommTimeouts.ReadTotalTimeoutConstant = 500;
m_CommTimeouts.WriteTotalTimeoutMultiplier = 500;
m_CommTimeouts.WriteTotalTimeoutConstant = 500;

// Configure
if (SetCommTimeouts(m_hComm, &m_CommTimeouts))
{
if (SetCommMask(m_hComm, EV_RXCHAR | EV_TXEMPTY | EV_CTS))
{
if (GetCommState(m_hComm, &m_dcbComm))
{
m_dcbComm.fRtsControl = RTS_CONTROL_ENABLE;
// set RTS bit high!
if (BuildCommDCB(szBaud, &m_dcbComm))
{
if (SetCommState(m_hComm, &m_dcbComm))
{
PurgeComm(m_hComm, PURGE_RXCLEAR | PURGE_TXCLEAR | PURGE_RXABORT | PURGE_TXABORT);
bResult = TRUE;
}
}
}
}
}

[ybdfeb]

我的本意是通过串口发送数据给一设备，然后等待该设备返回的数据。
我希望做到当线路或设备出现故障无法返回数据时，程序不会一直等下去。也就是说是个超时的问题。各位大虾有没有好办法.

[ybdfeb]

虽然设置了超时，但串口没有接收到数据时，GetOverlappedResult仍然会痴痴的等。这个地方一定要用定时器吗？