IOC Tips and Tricks

DBLoadRecordsLoop and DBLoadRecordLoop

You can load Db records in a loop using dbLoadRecordsLoop.

# Example usage of dbLoadRecordsLoop() and iocshCmdLoop() etc.
# Define a loop or list variable, then references to \$(VAR) will be replaced by loop/list values.
# You can use \$(VAR) in any of the values of the parameters, including the db file name.
# The loop/list variable "I" is passed to the DB file along with any other specified macros.
# We now loop "I" over a range of 1 to 3.
dbLoadRecordsLoop("db/utilitiesTest.db", "P=$(MYPVPREFIX),Q=A\$(I)", "I", 1, 3)

You can also iterate over a list using dbLoadRecordsList.

# Here S is our list variable with values x, Y and Z.
dbLoadRecordsList("db/utilitiesTest.db", "P=$(MYPVPREFIX),Q=A\$(S)", "S", "X;Y;Z", ";")

# As the loop/list variable is always passed though, we can instead iterate over Q.
dbLoadRecordsList("db/utilitiesTest.db", "P=$(MYPVPREFIX)", "Q", "BX;BY;BZ", ";")

You can execute IOC commands in loops as well.

# We can execute iocs commands in a similar way.
iocshCmdLoop("dbgrep $(MYPVPREFIX)A\$(I)*", "", "I", 1, 3)
iocshCmdList("dbgrep $(MYPVPREFIX)A\$(S)*", "", "S", "X;Y;Z", ";")

# We can also load files. The macro Q and I will be defined as temporary environment.
# variables for use in the script and then reset back to their pre-script values.
iocshCmdLoop("< st\$(I).cmd", "Q=Hello\$(I)", "I", 1, 2)

More details can be found at http://epics.isis.stfc.ac.uk/doxygen/main/support/utilities/dbLoadRecordsFuncs_8cpp.html#a32071967b99f42356b1e04b06746cc73.

N.B. If you need to parameterise your macro names, you will need to use a template and not a dbLoadRecordsList or dbLoadRecordsLoop.

Toggle multiple PV's from a single set-point

Sometimes you might want to have a single record set point that processes multiple records. An example of this would be for a device that requires different commands to be sent for Start and Stop. Rather than having to process two distinctly different records for each command you can use this template to toggle these from a single record:

record(bi, "$(P)TOG:RECORD:SP") {
	field(DESC, "Toggle record set point")
	
	field(ZNAM, "Record1")
	field(ONAM, "Record2")
	info(INTEREST, "HIGH")
}

# Add 1 to the value of the toggle set point to map the fanout 
# forward link index.
record(calcout, "$(P)_TOG:CALC:RECORD") {
	field(INPA, "$(P)TOG:RECORD:SP CP")
	
	field(CALC, "A+1")
	
	field(OUT, "$(P)_TOG:RECORD.SELN PP")
}

record(fanout, "$(P)_TOG:RECORD") {
	field(SELM, "Specified")
	
	field(LNK1, "$(P)_RECORD1:SP PP")
	field(LNK2, "$(P)_RECORD2:SP PP")
}

record(bo, "$(P)_RECORD1:SP") {
	field(DESC, "Process record1")
	field(DTYP, "stream")
	field(SCAN, "Passive")
	
	field(OUT, "@device.proto set_record1() $(PORT)")
}

record(bo, "$(P)_RECORD2:SP") {
	field(DESC, "Process record2")
	field(DTYP, "stream")
	field(SCAN, "Passive")
	
	field(OUT, "@device.proto set_record2() $(PORT)")
}

This takes the set points binary value, shifts it by +1 in a calc record which allows for it to be mapped with the forward link outputs of the fanout record, these forward links are then processed. This can be easily extended with additional forward links or sequence records.