Experimental Physics and
Industrial Control System

"Meyer, Markus via Tech-talk" <tech-talk at aps.anl.gov> · Fri, 12 Apr 2024 17:25:00 +0200

Dear all,

I am evaluating possibilities to communicate with a plc and other hardware
from beckhoff. I have successfully build the adsDriver [1] device support
and it seems to work very well for input variables. I can also write output
variables, but if the value gets changed on the plc itself (e.g. by the
interlock logic or by another connected protocol) it is not synced back to
the pv. It also seems that the current value is not initially read on
startup of the IOC.

For example, this is the pv definition:

record(ao, "$(P):IC:CB01-SSet") {
    field(DTYP, "asynFloat64")
    field(PREC, "2")
    field(EGU,  "%")
    field(DRVH, "100")
    field(DRVL, "-100")
    field(OUT,  "@asyn($(PORT) 0 0) REAL W P=PLC_TC3 V=HMI.IC.CB01.SSet")
    info(asyn:READBACK, "1")
}

Before I start the IOC, the plc value is set to 2. If I start the IOC, the
value of the pv is set to 0. The Timestamp is updated. The value in the plc
gets not changed. I expected, that the pv value is also set to 2. Writing a
value to the pv is working as expected.

Did I miss something here? What can I do to subscribe for changes of output
variables?

Thanks,
Markus

[1] https://github.com/Cosylab/adsDriver

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System