Use VTScada as a DDE Server

VTScada can be used as a DDE server. To do so, you must start VTScada with the command line switch, /d.

For example:

c:\Program Files\Trihedral\VTScada\VTScada_YourVersionNumber\vts.exe /d 

In your client program, you must provide address information for the VTScada program, the name of the running application, the names of the tags you wish to query, and the name of the property you want to obtain from each tag (usually '\value').

The most common use-case is to configure Microsoft Excel to display VTScada tag values in the cells of a spreadsheet. This can be done using a formula for each cell, as follows.

The formula has four parts: the name of the program (VTS), the name of the application, the name of the tag, and the property of the tag to obtain.

As entered in an Excel spreadsheet cell, the formula would have this form:

=VTS|'AppName'!'TagName\Value'

This formula is not literal. The various components are described in the following table.

If there are multiple display manager windows, the reference must be to a specific display manager session. The format changes to =VTS|'AppName 1' !'TagName\Value' (or 2, etc). Without this change, you will get an error message that Excel cannot start VTS.

If the tag name you've specified has spaces, back-slashes, or other characters that Excel might interpret as anything other than the name, then you must surround the 'Tag Name\Property' portion of the function with single quotes as shown. It is advisable to do this for every instance, whether required or not.

Syntax	Description
=	The equals sign (=) indicates to Excel that this is a formula.
VTS	VTS is literal, specifying the name of the program to access. If VTScada is not running when the spreadsheet opens, it will be started automatically.
|	The pipe character separates the program name from the document or topic name. (In the case of VTScada, this is the application name.)
AppName	Following the pipe character is the application name. Note: If the application name includes spaces, you must use single quotes to surround the name.
!	The exclamation point character is the topic item delimiter, separating the application name from the tag to which you are referring.
TagName	Following the exclamation point character should be the name of the tag whose data you want to report in the spreadsheet cell. The tag name should appear exactly as it is displayed in the name property of the tag properties folder.
\	The back slash character (\) is the scope operator, separating the tag name from the property or data to which you are referring.
Value	The name of one of the tag's properties, whose value you want to report in the cell. In most cases, this will be Value, but it could also be, Name, Area, Description, etc.

Formula Examples

The following formula examples have been provided to assist you in setting up Excel spreadsheet cells to read values from VTScada tags.

Given an application named, "DDE Test" and containing a tag named "AnalogInputTag"...

To display the tag's value in a spreadsheet cell:

=VTS|'DDE Test'!'AnalogInputTag\Value'

To display the name of the same tag's associated I/O device:

=VTS|'DDE Test'!'AnalogInputTag\IODevice'

To display the description of the same tag:

=VTS|'DDE Test'!'AnalogInputTag\Description'

The name of the tag configuration variable you are requesting must be written exactly as it occurs in the tag's code. If you are unsure, use the Source Debugger to examine an instance of the tag type.

Related information:

VTScada as a Local DDE Client - How VTScada can read from (and write to) a DDE server program.