Experimental Physics and
Industrial Control System

Hi Patrick –

The method that we use at ESS (based on the one at PSI) does handle the necessary build and load steps to deal with the situation that you describe. In short, we build and package EPICS modules (including sequencer-based applications) in a special way that allows you to have an IOC run using nothing more than a text file as a startup script, something like:

require my_snl_program

# other configuration

seq my_snl_program

iocInit

Since this simply a text file, it would of course be very simple to modify it based on whatever configuration needs you have.

For more documentation, please checkout our documentation here: http://e3.pages.esss.lu.se/

If you have any questions, feel free to ask.

Cheers,

Simon

Hi Patrick,

It is possible to build and load SNL programs as loadable plugins, we made that possible using the IOC's dlload command back in 3.15. I believe the PSI and ESS methods of building and booting IOCs use that, but I haven't tried it for a while and I forget what you have to do to create and load the DBD file that tells the IOC where the SNL code is. Someone from one of those EPICS sites may be able to help.

One other possibility you can consider is to build your SNL into a stand-alone program, so that code runs in a completely separate process from the IOC. That decouples the two and allows you to start and stop them independently, although you do have to ensure that the SNL code is properly written to handle waiting for all its CA connections at startup, and for the PVs going away and coming back when the IOC comes online again.

- Andrew