Re: Porting EPICS to NetBSD

[Andrew Johnson <anj@aps.anl.gov>]

David Dudley wrote:
> Just out of curiosity, are there any Industrial sites that use EPICS?
> I see lots of labs and observatorys and other academic environments,
> but don't think I've ever seen an industrial type site.

The EPICS website has a page that does list some industrial users at 
http://www.aps.anl.gov/epics/projects.php but that list is rather old 
now and I'm not sure how we got the information.

> Also, I've seen information on a MODBUS/TCP interface being
> available, and stuff for VME boxes (or "crates", I think you call
> them), but very little as far as actual industrial I/O interface
> availability.
>
> An industrial site (at least us), uses PLC networks traditionally
> with MODBUS being a favorite (not MODBUS/TCP, but just serial
> MODBUS). In addition, we have Allen Bradley Data Highway, Siemens
> TIWAY or TI505, DirectNet for the DirectLogic systems we use, DNP for
> a couple of our other PLC systems, and various other hardware
> interfaces like FieldBus or HART, and on, and on, and on.....  I
> haven't seen any of that level of flexibility in the stuff I've seen
> on EPICS as of yet.

Have you studied http://www.aps.anl.gov/epics/modules/index.php the 
support module pages yet?  Under the hardware support we list some of 
those serial protocols -- I know that there are sites using serial 
Modbus, we use DirectNet here, and there are many others.  For RS232 and 
other messagaging type support you should favor anything that says it 
uses Asyn, which is a fairly recent and flexible framework for doing 
this kind of I/O.  You should ask specific questions on tech-talk before 
starting on a driver, since someone else may have at least part of your 
solution already written.

> Don't get me wrong, I'm planning on writing a fair bundle of software
> that I'm actually going to download into some of our PLC equipment in
> order to convert them into IOC's themselves. We have roughly 40
> Motorola MOSCAD remote systems that I can download custom 'C'
> programs into, and I'm planning on making good use of that for IOC
> interaces, but at least a normal  MODBUS interface would be helpful
> in order to get things started easily (MODBUS is sort of the
> "universal" PLC interface, that practially everyone in the industry
> talks).  There are a lot of much better ones, but serial MODBUS is
> usually a 'least common denominator'.

IIRC that's also part of its downfall, and may be why we don't have it 
prominently listed - people have written an interface to 'their' PLC, 
but it doesn't work with someone else's without modification because of 
the lack of a rigid standard.  It would certainly be worth posting a 
tech-talk question with Modbus in the subject line to see how many 
solutions there are out there.

HTH,

- Andrew
--
Not everything that can be counted counts,
and not everything that counts can be counted.
  -- Albert Einstein