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Trying to write to Parallel Port causes exception

Posted on 2004-08-23
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Last Modified: 2013-11-20
I have some code that writes to a parallel port.  I have used both the C++ _outp and the InPOut32 dll.  Whenever accessing parallel port to begin output, I get a 0xc0000005 exception which I believe is an access denied.  If anyone has seen this, and can give me some advice, that would be great.

Thanks,

Matt
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Question by:neverrealm
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by:jkr
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This is an Access Violation, meaning that your code uses invalid memory addresses. Could you post your code?
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by:Jaime Olivares
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I have used the WinIO library (www.internals.com) with success, take a look to previous question:

http:/Dot_Net/VisualC_PLUS_PLUS_DOT_NET/Q_21045309.html

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by:neverrealm
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I think I may have figured out a way around this.  Do either of you guys know how to execute command line calls via VC++
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by:jkr
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You mean like

DWORD ExecuteAndWaitForCompletion   (   LPSTR   pszCmd)
{
   STARTUPINFO         si;
   PROCESS_INFORMATION pi;

   BOOL                bRes;

   DWORD               dwCode  =   0;

   MSG                           msg;

   ZeroMemory  (   &si,    sizeof  (   STARTUPINFO));

   si.cb           =   sizeof  (   STARTUPINFO);
   si.dwFlags      =   STARTF_USESHOWWINDOW;
   si.wShowWindow  =   SW_HIDE;

   bRes    =   CreateProcess   (   NULL,
                                   pszCmd,
                                   NULL,
                                   NULL,
                                   TRUE,
                                   NORMAL_PRIORITY_CLASS,
                                   NULL,
                                   NULL,
                                   &si,
                                   &pi
                               );

   while   (   WAIT_OBJECT_0   !=  MsgWaitForMultipleObjects   (   1,
                                                                   &pi.hProcess,
                                                                   FALSE,
                                                                   INFINITE,
                                                                   QS_ALLINPUT
                                                               )
           )
           {
               while   (   PeekMessage (   &msg,   NULL,   0,  0,  PM_REMOVE))
                       {
                           DispatchMessage     (   &msg);
                       }
           }

   GetExitCodeProcess  (   pi.hProcess,    &dwCode);

   CloseHandle (   pi.hProcess);
   CloseHandle (   pi.hThread);

   return  (   dwCode);
}

and call that like

ExecuteAndWaitForCompletion ( "ping.exe 192.168.0.1");

?

You could also use 'system()', but that pops up a console window.

WinExec( "ping.exe 192.168.0.1", SW_HIDE);

will work also if you don't have to wait for the command to finish.
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by:neverrealm
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Ok, the WinExec thing is exactly what I'm looking for, but it always comes up with a file_not_found error on copy C:\BarFile\label.bar LPT1.  I can type the same thing into the command line and it will print.
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by:Jaime Olivares
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you have to execute the "command prompt", something like:

WinExec( "cmd copy c:\\BarFile\\label.bar LPT1:");
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by:neverrealm
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Ok, that cured the file not found error in some instances, but it's still not performing the command, i.e., printing to LPT1
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by:Jaime Olivares
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Questions:
Are you writting "LPT1" or "LPT1:"
Is your printer actually connected to LPT1?
Is your printer enabled to work with DOS?
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by:neverrealm
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I tried both LPT1 and LPT1: and neither worked.  When I do a copy from the command prompt it works fine doing this:   copy c:\barfile\label.bar LPT1
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by:neverrealm
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I solved the problem.  I used a handle to the LPT1 port and wrote to the port the same way as with COM ports, without setting the state.
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