Experimental Physics and
Industrial Control System

Michael Davidsaver via Tech-talk <tech-talk at aps.anl.gov> · Thu, 24 Mar 2022 09:11:13 -0700

On 3/24/22 08:54, Jérôme Poincheval via Tech-talk wrote:

Hi tech-talk,

I am new to epics, and using it to read data from a keithley scpi multimeter.

I want to get one shot readings, not periodic ones. So, to trigger an 'on-demand' measurement, I write a value to the .PROC field of my passive record to trigger processing, then read the value.

This works well, but I wonder if there is a 'read-data-now' function in epics which I have overlooked ?

Not really.  Though I like to hide ".PROC" using a boRecord
so that OPI widgets can automatically show "Measure" as a label.

eg.

record(bo, "$(PORT):measure_v_dc") {
    field(ZNAM, "Measure")
    field(ONAM, "Measure")
    field(FLNK, "$(PORT):measure_v_dc_")
}
record(ai, "$(PORT):measure_v_dc_") {
    ... as below
}

##### excerpt from .proto file :

# one shot measurement
measure {
        ExtraInput = Ignore;
        out ":measure:\$1?";
        in "%f";
}

##### excerpt from .db file :

# read dc voltage, triggered by putting a value to measure_v_dc.PROC
record (ai, "$(PORT):measure_v_dc") {
        field (DESC, "voltage/dc one shot measurement")
        field (DTYP, "stream")
        field (INP,  "@scpi_keithley_2000.proto measure(voltage:dc) $(PORT)")
        field (SCAN, "Passive")
}

--
Jérôme Poinchevalpoincheval at lpccaen.in2p3.fr      tel:02.31.45.29.87
LPC Caenhttp://www.lpc-caen.in2p3.fr

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System