串口读不到数据 急

[yyfq521]

串口读不到数据，为什么？请各位高人指点
void CRS485CommDlg::OnReceive()
{
OVERLAPPED m_osRead;
memset(&m_osRead,0,sizeof(OVERLAPPED));
m_osRead.hEvent=CreateEvent(NULL,TRUE,FALSE,NULL);

COMSTAT ComStat;
DWORD dwErrorFlags;

char str[100];
memset(str,''\0'',100);
DWORD dwBytesRead=100;//读取的字节数
BOOL bReadStat;

ClearCommError(hCom,&dwErrorFlags,&ComStat);
dwBytesRead = min(dwBytesRead, (DWORD)ComStat.cbInQue);
bReadStat = ReadFile(hCom,str,dwBytesRead,&dwBytesRead,&m_osRead);
if(!bReadStat)
{
if(GetLastError()==ERROR_IO_PENDING)
{
WaitForSingleObject(m_osRead.hEvent, 2000);
}
}
PurgeComm(hCom, PURGE_TXABORT|PURGE_RXABORT|PURGE_TXCLEAR|PURGE_RXCLEAR);
m_disp = str;
UpdateData(FALSE);
}