Regarding System Error Code 995 in Serial Communication

[pra84veen]

hi one and all, iam having a problem with accessing serial port in my pc. i have developed an application which access the serial port in VC++ 6.0.After configuring the Serial port to 115200, iam able to send the data to the com port using WriteFile().But, iam unable to receive the data from the com port through ReadFile() operation and i have checked the error by using GetLastError() and it is given as 995(system error code).Even though i have restarted my system several times,iam unable to debug. Please help me why this error is getting and how to fix this error? Thanks in advance Regards, Praveen

modified on Monday, June 9, 2008 8:23 AM

[CPallini]

Cross post: http://www.codeproject.com/script/Forums/View.aspx?fid=1648&msg=2588888[^], please don't do it. BTW why didn't you post the relevant code, as I suggested? :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke

[pra84veen]

Iam calling this function for capturing data. The ReadFile() returns 0 value and GetLastError() gives error 995 bool CSerialPort::bReceiveBytes( unsigned char* x_pcBuffer, unsigned short x_usLengthExpected, unsigned short *x_pusLengthReceived ) { bool bResult = FALSE; unsigned long ulLengthReceived=0; int iResult; iResult = ReadFile( m_comPortHandle, x_pcBuffer[0], x_usLengthExpected, &ulLengthReceived, NULL ); DWORD err1 = GetLastError(); *x_pusLengthReceived = (unsigned short)ulLengthReceived; return( bResult ); }

[CPallini]

pra84veen wrote:

x_pcBuffer[0]

The above is wrong: you should use x_pcBuffer instead. :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke

[pra84veen]

hello, thanks for your reply... even though if i replace x_pcBuffer instead of x_pcBuffer[0], i dint get any data into the buffer. but here the return values for ReadFile is 1 but iam unable to capture the data.. Thanks & Regards, praveen

[CPallini]

When return value is 1, ReadFile succeeded. What is the value of ulLengthReceived? :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke

[pra84veen]

the value received by the ulLengthReceived is 0.

void CER2TSerialDlg::OnStartThread()
{
CWinThread *pThread = NULL;
m_SerialCommn->bOpen()
pThread = AfxBeginThread((AFX_THREADPROC)ReadFromModuleThread,NULL);
}

UINT CER2TSerialDlg::ReadFromModuleThread(LPVOID pPARAM)
{
unsigned char ucLengthExpected=10;
char chBuffer[FIFO_SIZE]={0};
unsigned short usReceived=0;

while(TRUE)
{
m_SerialCommn->bReceiveBytes(chBuffer,ucLengthExpected,&usReceived);
}
return 0;
}

bool CSerialPort::bReceiveBytes(char* x_pcBuffer,
unsigned short x_usLengthExpected,
unsigned short *x_pusLengthReceived )
{

unsigned long ulLengthReceived=0;
int iResult;
iResult = ReadFile(m_comPortHandle,
x_pcBuffer[0],
x_usLengthExpected,
ulLengthReceived,
NULL );
DWORD err1 = GetLastError();
*x_pusLengthReceived = (unsigned short)ulLengthReceived;
return( iResult );

}/

Regards praveen

modified on Wednesday, June 11, 2008 1:48 AM

[CPallini]

pra84veen wrote:

iResult = ReadFile(m_comPortHandle, x_pcBuffer[0], x_usLengthExpected, ulLengthReceived, NULL );

That's completely wrong (compiler doesn't complain, does it?). Should be:

ReadFile(m_comPortHandle,
x_pcBuffer,
x_usLengthExpected,
&ulLengthReceived,
NULL );

Please note the ampersand in front of ulLengthReceived. BTW: How did you set serial port timeouts? :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke

[pra84veen]

Even after modification also, iam not able to collect the data The serial port timeouts are

GetCommTimeouts(m_comPortHandle, &sCommTimeOuts);
sCommTimeOuts.ReadIntervalTimeout = 5;//100; //[ms]
sCommTimeOuts.ReadTotalTimeoutMultiplier = 1;//10; //[ms]
sCommTimeOuts.ReadTotalTimeoutConstant = 1;//500; //[ms]
sCommTimeOuts.WriteTotalTimeoutMultiplier = 1;//10; //[ms]
sCommTimeOuts.WriteTotalTimeoutConstant = 1;//100; //[ms]
SetCommTimeouts(m_comPortHandle, &sCommTimeOuts);

Thanks & Regards, Praveen

[CPallini]

Why don't you widen them (you can also set them for a blocking call, just to make a test)? :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke

[pra84veen]

sorry, i dint get you

[pra84veen]

even if i change the values of commtimeouts to

GetCommTimeouts(m_comPortHandle, &sCommTimeOuts);
sCommTimeOuts.ReadIntervalTimeout = 100; //[ms]
sCommTimeOuts.ReadTotalTimeoutMultiplier = 10; //[ms]
sCommTimeOuts.ReadTotalTimeoutConstant = 500; //[ms]
sCommTimeOuts.WriteTotalTimeoutMultiplier = 10; //[ms]
sCommTimeOuts.WriteTotalTimeoutConstant = 100; //[ms]
SetCommTimeouts(m_comPortHandle, &sCommTimeOuts);

i dint observe any change.