Argonne National Laboratory

Experimental Physics and
Industrial Control System

1994  1995  1996  1997  1998  1999  2000  2001  2002  2003  2004  2005  2006  2007  2008  2009  2010  2011  <20122013  2014  2015  2016  2017  2018  2019  Index 1994  1995  1996  1997  1998  1999  2000  2001  2002  2003  2004  2005  2006  2007  2008  2009  2010  2011  <20122013  2014  2015  2016  2017  2018  2019 
<== Date ==> <== Thread ==>

Subject: RE: What is void* puser in ca_create_channel
From: "Hill, Jeffrey O" <johill@lanl.gov>
To: Florian Feldbauer <florian@ep1.ruhr-uni-bochum.de>
Cc: EPICS tech talk <tech-talk@aps.anl.gov>
Date: Fri, 30 Mar 2012 14:10:16 +0000
> Just one other question: Can I use the CA methods ca_create_channel and
> ca_create_subscription within a c++ class?

Yes, the necessary 'extern"C"' bracketing is in the ca header files so that its C interface can be called from C++.

> Any idea based on this few information, or should I post my code?

If the CA client and its IOC are not on the same subnet then you may need to add the IOC's address to the EPICS_CA_ADDR_LIST environment variable for the client. Otherwise, if they are intended to be on the same subnet them make certain that both hosts are configured with the same subnet mask.

There are also some additional suggestions in the troubleshooting section of the CA reference manual.

Jeff

> -----Original Message-----
> From: Florian Feldbauer [mailto:florian@ep1.ruhr-uni-bochum.de]
> Sent: Friday, March 30, 2012 6:29 AM
> To: Hill, Jeffrey O
> Cc: EPICS tech talk
> Subject: Re: What is void* puser in ca_create_channel
> 
> Thanks for your answers.
> 
> Just one other question: Can I use the CA methods ca_create_channel and
> ca_create_subscription within a c++ class?
> The project we are working on should use OO techniques.
> We need not only an interface to EPICS, but also to a simulation.
> So we wanted to have an abstract base class, which is used by the rest
> of our project, and  derived classes for the implementation of
> the individual "control systems". One derived class would contain the CA
> for EPICS and another the interface to our simulation.
> 
> I can compile my test program for this object-structure, but I don't get
> a conncetion to my EPICS ioc.
> The two examples from makeBaseApp.pl are working correctly.
> 
> Any idea based on this few information, or should I post my code?
> 
> Best regards,
> Florian
> 
> On 03/29/2012 05:19 PM, Hill, Jeffrey O wrote:
> > Hi,
> >
> > The puser pointer you pass to ca_create_channel is saved by the library
> with the channel and is later supplied as a puser argument to your channel
> connectione state update callback function. There is also a ca function
> "void * ca_puser ( CHID )" that will return the puser pointer that was
> supplied when the channel was created.
> >
> > Likewise, the puser pointer you pass to ca_create_subscription is saved
> by the library with the subscription and is later supplied as a puser
> argument to your subscription update callback function.
> >
> >> How does this parameter have to look like?
> >> Can I use a C-Struct with any member I want to have (even members which
> >> are not for the CA, but for another part of my program)? Are there any
> >> members which are mandatory? (like value or chid)
> > A pointer to any data structure can be used. The CA library does not in
> any way access, or place any restrictions on the content of, this user
> application private data structure. The user application is of course
> responsible for allocation, initialization, maintenance, and de-allocation
> (proper cleanup) of this data structure.
> >
> > Use of void pointers passed to callbacks is an old technique which is
> roughly equivalent to a virtual function in modern software interfaces,
> BTW.
> >
> > HTH, and feel free to send any other questions that you might have, and
> I will do my best to answer them.
> >
> > Jeff
> >
> >> -----Original Message-----
> >> From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-
> bounces@aps.anl.gov]
> >> On Behalf Of Florian Feldbauer
> >> Sent: Thursday, March 29, 2012 4:01 AM
> >> To: EPICS tech talk
> >> Subject: What is void* puser in ca_create_channel
> >>
> >> Dear all,
> >>
> >> I currently write a CA Client that should monitor all measured
> >> temperatures in my experiment
> >> to regulate the chillers.
> >> This is my first try to program a CA Client, and I have a question
> >> concerning this:
> >>
> >> The ca_create_channel and the ca_create_subscription methods both have
> >> a parameter void* puser. How does this parameter have to look like?
> >> Can I use a C-Struct with any member I want to have (even members which
> >> are not
> >> for the CA, but for another part of my program)? Are there any members
> >> which are mandatory? (like value or chid)
> >>
> >> In the camonitor.c example generated with makeBaseApp.pl this puser is
> >> just a pointer to a C-Struct containing
> >> a c-string value, the chid and evid of the channel.
> >>
> >> Best regards,
> >> Florian
> >>
> >> --
> >> -------------------------------------
> >> | Florian Feldbauer                 |
> >> | Ph.D. student                     |
> >> |                                   |
> >> | Institut für Experimentalphysik I |
> >> | Ruhr-Universität Bochum           |
> >> | Universitätsstr. 150              |
> >> | D-44780 Bochum                    |
> >> |                                   |
> >> | Office: NB 2/173                  |
> >> | Phone:  (+49)234 / 32-23538       |
> >> | Fax:    (+49)234 / 32-14170       |
> >> | Web:    http://www.ep1.rub.de     |
> >> -------------------------------------
> 
> 
> --
> -------------------------------------
> | Florian Feldbauer                 |
> | Ph.D. student                     |
> |                                   |
> | Institut für Experimentalphysik I |
> | Ruhr-Universität Bochum           |
> | Universitätsstr. 150              |
> | D-44780 Bochum                    |
> |                                   |
> | Office: NB 2/173                  |
> | Phone:  (+49)234 / 32-23538       |
> | Fax:    (+49)234 / 32-14170       |
> | Web:    http://www.ep1.rub.de     |
> -------------------------------------



Replies:
Re: What is void* puser in ca_create_channel Florian Feldbauer
References:
What is void* puser in ca_create_channel Florian Feldbauer
RE: What is void* puser in ca_create_channel Hill, Jeffrey O
Re: What is void* puser in ca_create_channel Florian Feldbauer

Navigate by Date:
Prev: Re: What is void* puser in ca_create_channel Benjamin Franksen
Next: Re: Problems in using VX2 motor controller Ron Sluiter
Index: 1994  1995  1996  1997  1998  1999  2000  2001  2002  2003  2004  2005  2006  2007  2008  2009  2010  2011  <20122013  2014  2015  2016  2017  2018  2019 
Navigate by Thread:
Prev: Re: What is void* puser in ca_create_channel Florian Feldbauer
Next: Re: What is void* puser in ca_create_channel Florian Feldbauer
Index: 1994  1995  1996  1997  1998  1999  2000  2001  2002  2003  2004  2005  2006  2007  2008  2009  2010  2011  <20122013  2014  2015  2016  2017  2018  2019 
ANJ, 18 Nov 2013 Valid HTML 4.01! · Home · News · About · Base · Modules · Extensions · Distributions · Download ·
· Search · EPICS V4 · IRMIS · Talk · Bugs · Documents · Links · Licensing ·