GRAccess Toolkit: Configuring the OPCClient DIObject

Application Versions

To execute the GRAccess sample application that is described in this document, you will need the following prerequisites:

• Visual Studio 2005
• Industrial Application Server 2.1 or later
• DASABTCP DAServer or any other OPC Server

Using the IDE to Configure the OPCClient DIObject

Before describing using GRAccess to manipulate the OPCClient object, we’ll describe the final goal by demonstrating first the manual steps using the ArchestrA IDE.

1. First create a derived template of the OPCClient DIObject.
2. Give the new derived template the name $OPCClient_02 and open the template editor.

   
   Figure 1: Editing the Derived Template

3. Click the General tab and set the Server node to localhost. Then select a registered OPC Server from the Server name list.
4. Click the Scan Group editor tab.
5. In the Scan Group tab add a new Scan Group called Group1. Then select Group1.
6. Add two Attributes and name them Counter_1 and Counter_2. Assign the Item Reference N100:1 to Counter_1 and N200:1 to Counter_2.

   
   Figure 2: Configure Scan Groups

7. Save and close the object.

What Happens at the API Level

This section describes in GRAccess API terms what happened under the hood during the configuration of the OPCClient DIObject:

Configure the Common Attributes

Query the Galaxies and Login

Galaxies = GR.QueryGalaxies(GRMachineName);
G = Galaxies[GalaxyName];
G.Login(UserName, Password);

Get the $OPCClient Template and Derive a New Template

string[] Names = { “$OPCClient” };
Objects = G.QueryObjectsByName(EgObjectIsTemplateOrInstance.gObjectIsTemplate, ref Names);
T = (ITemplate)Objects[1];
Parent = T.CreateTemplate(OPCClientTemplateName, true);

Checkout Template

Parent.CheckOut();

Configure ServerNode and ServerName Attributes

MxValue v = new MxValueClass();
//Configure computer name of OPCServer
v.PutString(OPCServerComputer);
Parent.Attributes[“ServerNode”].SetValue(v);
//Configure OPC server name
v.PutString(OPCServerName);
Parent.Attributes[“ServerName”].SetValue(v);

Add ScanGroup and an Attribute Array of Items

//Configure OPCGroup name
v.PutString(OPCGroupName);
Parent.Attributes[“_ScanGroupAdd”].SetValue(v);
//Add list of alias names to Group1
a.Empty();
v.PutString(OPCItemAttributeName1);
a.PutElement(1, v);
v.PutString(OPCItemAttributeName2);
a.PutElement(2, v);
Parent.Attributes[OPCGroupName + “._ItemAdd”].SetValue(a);

Figure 3: Object Properties

Save and CheckIn

Parent.Save();
Parent.CheckIn(“”);

Configure Item Attribute Alias Names

The configuration of the item alias mapping table is the tricky part of this procedure, because the attribute name-to-item association is stored as XML string in an element called [ScanGroupName].AliasDatabase.

The ArchestrA item attributes are XML elements in this XML file and the alias names are XML attribute of the item elements. To modify the mapping, the XML string needs to be retrieved from the attribute, the XML nodes need to be modified and then the modified XML string copied back into the original ArchestrA attribute.

Figure 4: XML Modifications

Get Group1.AliasDatabase XML

v = Parent.Attributes[OPCGroupName + “.AliasDatabase”].value;
string ItemDBXMLString = v.GetString();
//Create an XML document instance, and load XML data from AliasDatabase attribute
XmlDocument doc = new XmlDocument();
System.IO.StringReader SR = new System.IO.StringReader(ItemDBXMLString);
System.Xml.XmlTextReader TR = new System.Xml.XmlTextReader(SR);
doc.Load(TR);

Use XPath to Modify Item Names in XML

//XPath query to the actual items
XmlNodeList nodeList = doc.SelectNodes(“/ItemsList/Item”);
//Modify items list to point to the actual item names
XmlNode Item1 = nodeList[0];
Item1.Attributes[“Name”].Value = OPCItemName1;
XmlNode Item2 = nodeList[1];
Item2.Attributes[“Name”].Value = OPCItemName2;
string NewItemDBXMLString = doc.OuterXml;

Checkout Template

Parent.CheckOut();

Change Group1.AliasDatabase attribute with new XML

v.Empty();
v.PutString(NewItemDBXMLString);
Parent.Attributes[OPCGroupName +”.AliasDatabase”].SetValue(v);

Save and CheckIn

Parent.Save();
Parent.CheckIn(“”);

The Complete Source File

View the complete program file. You can copy/paste the content to a .cs file at your convenience.

Compilation

To compile the program.cs file run the following command in the Visual Studio 2005 command prompt:

csc /out:CreateOPCClient.exe program.cs /r:”C:\Program Files\Common Files\ArchestrA\ArchestrA.GRAccess.dll”;

Test Run

To execute CreateOPCClient.exe run the following command. In the following command line PENGUINS is the Galaxy name. Change it to reflect your server name:

CreateOPCClient gr=localhost g=PENGUINS u=Administrator pw=ww on=$OPCClient_02 os=ArchestrA.DASABTCP.1 oc=localhost og=Group1 oi1=N100:1 oa1=Counter_1 oi2=N200:1 oa2=Counter_2

Summary

The key to configuring an OPCClient DIObject using the GRAccess toolkit is the knowledge that the alias item names are stored in a single attribute as XML string. Modifying this string will create the mappings as seen in the OPCClient object’s Scangroup editor.