Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Tue, 8 Jul 2014 15:38:27 -0500

Hi Piotr,

I hope others on the tech-talk list will respond too, although I doubt
if anyone will be able to respond to your questions about the specific
comparisons. I just have a couple of points

On 07/08/2014 09:43 AM, Piotr Sybilski wrote:
> -          DDS,
> -          OPC UA,
> -          EPICS.

> The table doesn’t show the clear winner but emphasizes that the DDS and
> OPC UA have brighter future, higher market share and better support.

I don't know how you measured those particular characteristics, so I
can't really agree with them. Since EPICS is not sold commercially its
market share is by definition zero, but it does have quite a lot of
users (not very many in the Astronomy community, but there are a few
telescopes using it) and commercial companies who can support it.

What will be the on-going costs of supporting the other technologies,
and how long will you be able to get support for them? I don't know much
about DDS or OPC UA at all, but many commercial packages stop being
maintained within 5 years of their release, or the cost of maintenance
goes up significantly. Continually upgrading to the latest version of
your infrastructure software is not easy or cheap to do, but may be
necessary to maintain support from your supplier.

Since EPICS is completely open source, even if the rest of the EPICS
community were to go away (which is very unlikely) you will always be
able to find and fix problems in the code yourself, or pay for a third
party company to do so.

> I would be grateful for pros and cons of each technology that you can
> provide (our typical astronomical observatory consist of tens of
> devices, some of them redundant, real time communication is not required
> but quick event propagation and QoS is welcomed, some devices are simple
> sensors, some simple actuators, there are few devices that can produce
> bursts of data, for example CCD camera can produce 200 MB in one second,
> the data doesn’t have to be propagated through the system immediately,
> but shouldn’t choke the communication, some kind of prioritization is
> welcomed).

The technologies you use in astronomy are similar to those used by the
other large physics instruments that use EPICS, although in many cases
they will have many more devices than you. CCDs and other high-speed
imaging detectors are now common in light sources, and simple sensors
and actuators are extremely widely used.

EPICS should allow you to interface to almost any device you can
purchase, using either common communications standards or a
manufacturer's interface library. We also run on all the main operating
systems and CPU architectures, and the Channel Access network protocol
interoperates seamlessly between different architectures and software
versions.

HTH,

- Andrew
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System