DDE vs OPC for RSLinx. Alternatives?

After using DDE in my PC applications for many years to interface to PLC programs through RSLinx, I'm FINALLY looking at trying to use a more up to date and robust method.

The only alternative I seem to be finding is to use an OPC client. But with all of the associated fees and licensing, that's turning out to be an overly expensive proposition for the kinds of applications I have in mind.

Am I missing something? Or should I just go back to using DDE and forget it?

Hello,

You do not say which programming environment you are using. Writing a fixed OPC client is not too difficult and there are many sources of information. Also, depending on the development platform, there might be some low cost SDK.

This site might help: http://www.opcconnect.com/

What kind of applications? Are you linking to programs like Excel through DDE?

If you are developing just standard desktop apps with Visual Studio, AdvancedHMI gives you a completely free tool kit with drivers for AB PLCs.

Thanks for your quick replies, Mark and Archie!

Traditionally, I've used VB6 for the DDE applications just because I knew how to do those 'quickly.' But I'd like to switch that over to VS2012 or higher. I was looking at using NDde from CodePlex if I need to stick with DDE. But I'd prefer to go to a more modern method if there is one available. I can probably justify a some dollars for it. But the prices I've seen so far put those alternatives (OPC) out of reach.

I'll take a look at the www.advancedhmi.com site and see what's available there.

You'll find that AdvancedHMI works with Visual Studio 2015 Community Edition which is also free. Since the software is open source, it complies with Microsoft's license for using Community Edition for free.

If you're used to using RSLinx and DDE, you'll find a huge difference in the AdvancedHMI native driver for ControlLogix. In testing, the driver had shown update rates as fast as 4ms. A lot of the functionality in AdvancedHMI doesn't even require writing a single line of code, but if you do, writing code is much simpler. You can read a PLC value with just one line of code.

There is a Quick Start on the web site that will get you up and running in just a few minutes after VS is installed.

Archie,

Thanks so much! This looks very promising for what I need.