Experimental Physics and
Industrial Control System

"Kasemir, Kay" <[email protected]> · Thu, 5 Feb 2015 18:09:30 +0000

Hi:

Yes, for getting data from python into EPICS, using Channel Access it definitely a worthwhile approach.
You can add CA server to python so that it serves the data right away,
or add a CA client to python which writes the data to records in a "real" IOC as Tim explains.

The CA client approach is less code, especially if you already have an IOC.

An advantage of the CA server approach:
When using cainfo to see where the PV is coming from, you can (with a few intermediate steps) identify the python process.
If the python process crashes, you'll know, because the PV is gone.
With the python-client-writes-to-IOC approach, the python code is a layer removed.
If the python client crashes, your PV simply won't update, and you might notice that too late.

Rod's suggestion to turn the python script into a simple TCP server, then read that via stream device can be in-between:
Not too much code, and stream device will tell you right away about read errors when the python process dies.

-Kay

On Feb 5, 2015, at 12:56 PM, "Mooney, Tim M." <[email protected]>
 wrote:
> I just wrote some python code...write the sensor value to an EPICS PV

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System