BO which should switch to 1 whenever processed

[Majer Karel via Tech-talk <tech-talk at aps.anl.gov>]

Hello,

I would like to have a BO record which sets its value to 1 whenever processed (without necessarily writing 1 to VAL), then back to 0.

It's part of PLC-based motion control IOC. The database should allow moving the motor to saved waypoint positions; it looks like this:

record(ao, "AbsPos") {

    field(EGU,  "step")

}

record(ao, "Waypoint1") {

    field(EGU,  "step")

}

record(longout, "WaypointIdx") {

    field(FLNK, "SelectAbsPos")

}

record(sel, "SelectAbsPos") {

    field(SELM, "Specified")

    field(NVL,  "WaypointIdx")

    field(INPA, "AbsPos")

    field(INPB, "Waypoint1")

    field(FLNK, "DesiredPos")

}

record(ao, "DesiredPos") {

    field(EGU,  "step")

    # field(OUT,  "OUTLINK")  link to PLC

    field(DOL,  "SelectAbsPos")

    field(OMSL, "closed_loop")

    field(FLNK, "MoveToPos PP")

}

The processing chain is WaypointIdx -> SelectAbsPos -> DesiredPos -> MoveToPos

MoveToPos is a BO which tells the PLC to start motion, and it must have HIGH field set to non-zero. I'm having a problem triggering its processing in a way that its value becomes 1.

I tried this:

Record(bo, "MoveToPos) {

    # field(OUT,  "OUTLINK")  link to PLC

    field(DOL,  "1")

    field(OMSL, "closed_loop")

    field(HIGH, "1)

}

I expected that processing the record would set VAL to 1, then back to 0 after 1 second. It works only once; subsequent processing does not switch value back to 1. Writing 1 into VAL works as expected. Is this the correct functionality of the BO record?

I ended up with the following construct, which provides the desired functionality, but I don't much like having a record which only holds a constant value to be put into the BO. Is there a better way to do this?

record(ao, "DesiredPos") {

    field(EGU,  "step")

    # field(OUT,  "OUTLINK")

    field(DOL,  "SelectAbsPos")

    field(OMSL, "closed_loop")

    field(FLNK, "Constant1")

}

record(longout, "Constant1") {

    field(VAL,  "1")

    field(OUT,  "MoveToPos PP")

}

record(bo, "MoveToPos") {

    field(HIGH, "1")

}

Thanks,

Karel

Karel Majer | Senior software developer
Phone: +420 266 051 514
E-mail: karel.majer at eli-beams.eu

ELI Beamlines Facility|The Extreme Light Infrastructure ERIC Za Radnicí 835, 252 41 Dolní Břežany, The Czech Republic www.eli-beams.eu