Certification… Once Again

I need, really need, to discuss DeviceNet and EtherNet/IP certification once again.

Some automation people seem to think that certification is a “magic bullet”. If my device passes ODVA certification testing and I have that little certificate on my wall, my product is functionally sound. I won’t have any field problems.

That couldn’t be more wrong.

The DeviceNet certification process or the EtherNet/IP certification process is really just about the networking component of your product. It has nothing to do with your I/O, your logic or the overall functionality of your product.

Certification simply indicates that your product seems to play nice on the network as far as the kinds of messages you send out under specific circumstances. It doesn’t imply any kind of functional performance.

In fact the ODVA Certification process doesn’t look at your I/O data. It simply checks that your unit is sending the right number of bytes and that it appropriately handles network abnormalities. It makes sure that your device closes connections on timeouts, properly handles missing fragments of fragmented messages, resends messages when required, properly opens and closes connections. There are literally hundreds and hundreds of such things that an EtherNet/IP or DeviceNet device must do. The day long certification test tries most of them but not all.

Your application code in your product can be absolutely crap and you can still pass certification. If you have a valve device and half the time you don’t open the valve when you receive a DeviceNet I/O bit to open, you’ll still pass certification. It doesn’t matter to the test what you do or don’t do with the data you receive from the network.

YOU STILL NEED TO TEST YOUR DEVICE. Certification should be only a small part of your overall test strategy. Even if you get a daughtercard or software or some other network component from a reputable vendor you should still plan on a multi part test strategy. The vendor will certify their part but it will be up to you to validate your application logic in conjunction with the networking component.

This kind of testing will usually mean setting up a Rockwell PLC and thoroughly exercising your code just like it will be used by your customer. You should know up front that this won’t be inexpensive. The Rockwell PLC and software you need to drive it are very expensive. But that’s the price of being in the game.

If you have any specific certification questions, give me a call. We can do a pre-certification test on your product and shepherd it through the ODVA Lab for you. That’s usually a lot better than paying hundreds of dollars an hour to work with the ODVA Lab guys on a sophisticated network problem that you may not really understand.