Experimental Physics and
Industrial Control System

Ned Arnold <[email protected]> · Wed, 27 Oct 1999 16:51:09 -0500 (CDT)

> 
> Has anyone created a record or simple pattern of records that acts as a 
> watchdog?  In other words, one that will give a signal if a response does 
> not come back from a hardware device within a setable time period.
> 

Well, kind of. 

A simple calc record that decrements every scan can act as a watchdog. If
whatever you are watchdogging simply loads a constant into the val field
often enough such that it doesn't decrement to 0, then a 0 would indicate
the timeout. If you make it a calcout record, you could poke something
else with the out link when the watchdog expired.

record(calcout,"$(S):imageBusy") {
        field(SCAN,"1 second")
        field(CALC,"A<=0?0:A-1")
        field(INPA,"$(S):imageBusy.VAL NPP NMS")
        field(OUT,"$(S):imageBusyReset.PROC PP MS")
        field(OOPT,"When Zero")
        field(DOPT,"Use OCAL")
        field(OCAL,"0")
}

Something better write to $(S):imageBusy.VAL before it gets to 0 ...

This can be used to determine in the database if a particular client is running.
The client simply writes a value to $(S):imageBusy.VAL periodically or the
database assumes its not active.

	Ned

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System