Showing posts with label OPC-DA. Show all posts
Showing posts with label OPC-DA. Show all posts

Thursday, April 17, 2008

Linux obsession on the forums

Lately the usual PLC forums have been unusually chatty about Linux. Perhaps it's the recent Windows update that installed the new version of the .NET Frameworks 2.0, the trend toward Open Office and Star Office, or the successful home experimentation with Ubuntu and Fedora. There's also been more complaints than ever about the complicated and equally crappy DCOM basis of OPC, which gets (probably unfairly) pinned on Microsoft. The OPC Foundation gets to be the knight in shining armor with UA. General users are correctly getting the sense that configuration, specifically security, need not be complicated and that getting rid of the old also brings the freedom ditching the entire (Windows) platform.

The consensus seems to be that programming software will remain Windows based for some time. Until users put the pressure on - and they're complaining, but not applying diddly-squat, nothing will change in that area. So it's a 90% solution - control systems can be chosen on a platform independent decision, but integrators will still be running around with Windows laptops to program the PLCs. That doesn't bother me too much. First, they break the things every couple of years - about as often as Windows seems to fail. Second, there's always virtualization, which has been getting easier and cooler over time.

I welcome the simplicity of the newer Linux build frondends and their (always) powerful backend. I remember when the thrill of playing with a new Linux system came to an abrupt halt when you realized that your devices weren't supported and the user interface sucked! It's great to see "normal users" have such a positive experience with installing such a new, foreign, system. If only they knew the complexity of the innards! Thank god they don't - they're users.

Tuesday, December 4, 2007

OPC-HDA, what a bummer!

An integrator recently inquired about connecting FactorySQL to an OPC-HDA (historial data access) Server. A reasonable request. Hey, we're standardizing on OPC (DA) so why not? It seems reasonable that a historical data specification could bring some good to the table.

It turns out that OPC-HDA is another outdated COM based specification that was designed to standardize access to all of the different historian packages. Suppose you wanted a simple ActiveX graph or table back in the day. The idea is that it wouldn't have to know about the PLC. But wait, it still doesn't know how to poll the historical data. The user still needs to subscribe to tags, choose time ranges, etc. Sound like something that SQL's good at? Yeah, makes sense to use a standard interface. Plus, this many years later, all the vendors have jumped on the SQL bandwagon. And for good reason!

At this stage I can't even think of a practical way that FactorySQL could OPC-HDA that would make sense. Maybe if you needed to log from or write to an old HMI, but why? Logging works better from the PLC directly. Why would you ever need to write to an old HMI? It could only introducing unnecessary complexity and potential points of failure.

Aghh! Hurry, OPC-UA! We want web services! XML! Security models! NO MORE COM! Microsoft killed it so many years and major versions ago. Why can't industrial software follow suit!?!!? (I have my explanations, but will leave for another time)