WriteFile Error

Hi guys,

I'm quite new to this area but've managed to get some help from online
searches
and created the following program. A bit crude & messy for now. I
apologise for that.

However, I'm unable to send any bytes using WriteFile. Kept on getting
error.

Here's the code which I'm having an issue with :

------------------------------------------------------------------

LPSTR szText;
UCHAR * cl;
unsigned long BytesWritten;
bool bResult;

cl = converted_value_str;
_tochar sztext((char *)cl);
DWORD write = sizeof(cl);
if( ! PurgeComm( h, PURGE_TXABORT | PURGE_RXABORT | PURGE_TXCLEAR |
PURGE_RXCLEAR ) )
{
printf("\nPurgeComm error!!");
}

bResult = WriteFile(h, cl, sizeof(cl) + 1, &BytesWritten, NULL);
DWORD dw1 = GetLastError();
printf("\nbResult1 = %b", bResult);
printf("\nGetLastError1 = %u", dw1);
printf("\nsizeof(cl) = %i", sizeof(cl));
printf("\nBytesWritten1 = %u", &BytesWritten);

------------------------------------------------------------------

This is the error which I've got :

Enter a command (y/n) : y
Please enter a long string: 11

Buf_Len = 2
GetLastError1 = 87
sizeof(cl) = 4
bResult1 = 0
BytesWritten1 = 9305948

Can someone advise me why I'm having this error and how I can send any
data to my serial port? Fyi, I'm using COM1. Pls help!! Need this
urgently for my project.

Thanks in adv!


Yours Sincerely,
GK

William
Mon Apr 26 10:28:31 CDT 2004

"Reis" <gkteo@yahoo.com> wrote in message
news:fec512cd.0404260656.55ba9d33@posting.google.com...
> I'm quite new to this area but've managed to get some help from online
> searches and created the following program. A bit crude & messy for now. I
> apologise for that.
>
> However, I'm unable to send any bytes using WriteFile. Kept on getting
> error.

The error that you are getting is defined in

<winerror.h>

It is signaling an invalid parameter. Did you open the device with the
FILE_FLAG_OVERLAPPED bit set? If so you must pass the address of an
OVERLAPPED structure and not a NULL pointer.

Regards,
Will

Scott
Mon Apr 26 13:04:09 CDT 2004

Reis wrote:

> Hi guys,
>
> I'm quite new to this area but've managed to get some help from online
> searches
> and created the following program. A bit crude & messy for now. I
> apologise for that.
>
> However, I'm unable to send any bytes using WriteFile. Kept on getting
> error.
>
> Here's the code which I'm having an issue with :
>
> ------------------------------------------------------------------
>
> LPSTR szText;
> UCHAR * cl;
> unsigned long BytesWritten;
> bool bResult;
>
> cl = converted_value_str;
> _tochar sztext((char *)cl);
> DWORD write = sizeof(cl);
> if( ! PurgeComm( h, PURGE_TXABORT | PURGE_RXABORT | PURGE_TXCLEAR |
> PURGE_RXCLEAR ) )
> {
> printf("\nPurgeComm error!!");
> }
>
> bResult = WriteFile(h, cl, sizeof(cl) + 1, &BytesWritten, NULL);
> DWORD dw1 = GetLastError();
> printf("\nbResult1 = %b", bResult);
> printf("\nGetLastError1 = %u", dw1);
> printf("\nsizeof(cl) = %i", sizeof(cl));
> printf("\nBytesWritten1 = %u", &BytesWritten);
>
> ------------------------------------------------------------------
>
> This is the error which I've got :
>
> Enter a command (y/n) : y
> Please enter a long string: 11
>
> Buf_Len = 2
> GetLastError1 = 87
> sizeof(cl) = 4
> bResult1 = 0
> BytesWritten1 = 9305948
>
> Can someone advise me why I'm having this error and how I can send any
> data to my serial port? Fyi, I'm using COM1. Pls help!! Need this
> urgently for my project.
>
> Thanks in adv!
>
>
> Yours Sincerely,
> GK

It is not clear what you are doing to cl, but it is probably an invalid
address. Also, sizeof(cl) is always going to be 4 because it is a
pointer type. You can't use sizeof to get the size of a string.

--
Scott McPhillips [VC++ MVP]

gkteo
Mon Apr 26 20:04:19 CDT 2004

"William DePalo [MVP VC++]" <willd.no.spam@mvps.org> wrote in message news:<#2qxeM6KEHA.1000@TK2MSFTNGP11.phx.gbl>...
> "Reis" <gkteo@yahoo.com> wrote in message
> news:fec512cd.0404260656.55ba9d33@posting.google.com...
> > I'm quite new to this area but've managed to get some help from online
> > searches and created the following program. A bit crude & messy for now. I
> > apologise for that.
> >
> > However, I'm unable to send any bytes using WriteFile. Kept on getting
> > error.
>
> The error that you are getting is defined in
>
> <winerror.h>
>
> It is signaling an invalid parameter. Did you open the device with the
> FILE_FLAG_OVERLAPPED bit set? If so you must pass the address of an
> OVERLAPPED structure and not a NULL pointer.
>
> Regards,
> Will


Hi Will,

thanks for your help. I will change the WriteFile() parameters. Btw,
is there a limitation to WriteFile()? I need to send in cmd characters
to my printer but it keeps printing "12" instead. 12Hex is the command
I wish to send to the printer. Pls advise.

Thanks for your help.

Best Regards,
Reis