Sharing Global Data between a DLL and WinCC

Iyad

Hi every body,

Does anyone has an idea about this subjet?

Thanks.

EXPORTS
GetValue
SetValue

SECTIONS
.shared READ WRITE SHARED
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////
Where the Key EXPORTS defines the functions that this DLL will export, and mainly the Key SECTIONS defines a section call ".shared" with read/write acess.

In CPP of this DLL I created the following entries:
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////
#pragma data_seg(".shared")
short nValue = 0;
#pragma data_seg()

__declspec(dllexport) short GetValue(void){
return nValue;
}

__declspec(dllexport) void SetValue(short tnValue){
nValue = tnValue;
return;
}
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////
Where exists two functions, one to read the value of variable nValue and other to write the value of variable nValue. The convention __declspec(dllexport) force the convetion to export functions/variables/class.
The most important in this code is the sections created by #pragma data_seg(".shared")/#pragma data_seg(), because without him, the variable nValue would haven't the same scope between process, therefore would not be possible to share her.

Ok, now is only necessary to create the applications that will to use this dll calling the functions SetValue and GetValue to have accessin thevariable.

In WinCC, you can make this, with code below:
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////
#pragma code("C:\CC_SHAREPROJECT\VC_Project\Release\DLLShare.dll")
short GetValue(void) ;
short SetValue(short nValue);
#pragma code ()
printf("Reading value from DLL****************************************************\n");
SetTagWordWait("ShareData",GetValue());
printf("Reading OK******************************************************************\n");
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////

In WinCC, you can make this, with code below:
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////
Public Declare Function GetValue Lib "C:\CC_SHAREPROJECT\VC_Project\Release\DLLShare.dll" () As Integer
Public Declare Sub SetValue Lib "C:\CC_SHAREPROJECT\VC_Project\Release\DLLShare.dll" (ByVal tnValue As Integer)
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////

In both case, take care in the path of DLL.

In this simple example, I'm not worrying with the synchronization in the access of this functions, but in a real application would be necessary the use of MUTEX to to guarantee a safe access about these functions. See the post /tf/WW/en/Posts/7740

I put the source files, compiled files and the WinCC projetc in address:
http://discovirtual.uol.com.br/disco_virtual/jzte/Marcio/sharing/CC_SHAREPROJECT.zip, because the maximum file size in the forum is 1MB, and this file has 2MB.
To download the file, use the password 1234.
Unzip the file in the C unit, following the structure:
C:/
+CC_SHAREPROJECT
++VB_Project
++VC_Project
++WINCC_Project

I hope to have helped