Experimental Physics and
Industrial Control System

Benjamin Franksen via Tech-talk <tech-talk at aps.anl.gov> · Thu, 5 Mar 2020 19:16:08 +0100

Am 05.03.20 um 17:25 schrieb Ralph Lange via Tech-talk:
> When an IOC boots, it starts its components in a specific order.
> At the time when PINI=YES records are being processed, Channel Access is
> simply not fully up yet.
> 
> Note that for a while PINI has been a menu with different options. Maybe
> you can get your record processed in a later stage that way.

We looked into that and tried RUN and RUNNING but that didn't help.
Unfortunately there is no CA_READY state...

What we want to do here is write a string to an input link field once at
init time. Link fields can be written to only via CA, which is why we
have to use a CA link.

What would be required for a clean solution is some sort of notification
when the CA link is up and usable. I like Andrew's idea (mentioned in
the thread cited by Lewis): set the DTYP to "Async Soft Channel".
However, this doesn't work either. I think this is because trying to
write via an inoperational CA link does not trigger a callback; instead
the call to dbCaPutLinkCallback fails, so the device support returns the
status and does not set PACT.

A more reliable work-around than just waiting for some arbitrary amount
of time could be to monitor the severity + status of the record (with a
calcout) and trigger processing say every second until it is no longer
LINK/INVALID.

The "Async Soft Channel" support could do something like that
automatically if it sees dbCaPutLinkCallback failing. It could at least
do this once (or a fixed number of times) before ultimately failing.
That is, if dbCaPutLinkCallback fails, we set up a timed callback and
try again after a second or so, keeping the record in PACT state in the
meantime.

Cheers
Ben

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System