Re: Can we set 'NELM' tobe a variable in waveform or subArray?

[Mark Rivers via Tech-talk <tech-talk@aps.anl.gov>]

For the waveform record NELM is the maximum number of elements and cannot be changed a run time. However, NORD is the actual number of elements currently in the array, and it can be changed at run time. 

Please explain what you are trying to do. I suspect that you should be able to use NORD.

Mark

Sent from my iPhone

On Aug 20, 2023, at 3:21 PM, Kevin via Tech-talk <tech-talk@aps.anl.gov> wrote:



Hello everyone,

    

I used waveform to read  8 channels data, the waveform record is:

record(waveform, "$(P)Countxxyy")

{

  field(DTYP, "stream")

  field(INP, "@ct0801f.proto Counters_in  $(PORT)")

  field(NELM, "8")

  field(FTVL, "LONG")

  field(SCAN, "$(SCAN)")

}

The user hope that the NELM is a variable,  so I used $(P)N  to controller the readout numbers:

record(waveform, "$(P)Counters")

{

  field(DTYP, "stream")

  field(INP, "@ct0801f.proto Counters_in  $(PORT)")

  field(NELM, "$(P)N")

  field(FTVL, "LONG")

  field(SCAN, "$(SCAN)")

}

 When $(P)N changed, the $(P)Countxxyy keep an initial value. I think that the NELM can not be modified:

<2A371D12@F3664E2C.578BE164.png.jpg>

Then I found the modify property about NELM in subArray is ‘yes’,

<058F0953@EEFA6B62.578BE164.png.jpg>

So I changed the record like this:

record(waveform, "$(P)Counters")

{

  field(DTYP, "stream")

  field(INP, "@ct0801f.proto Counters_in  $(PORT)")

  field(NELM, "8")

  field(FTVL, "LONG")

  field(SCAN, "$(SCAN)")

}

record(subArray,"$(P)Countersxy") {

  field (DESC, "Read counterx~countery")

  field (INP, "$(P)Counters")

  field (MALM, "8")

  field (NELM, "$(P)N")

  field (INDX, "0")

  field (SCAN, "$(SCAN)")

}

When the $(P)N changed tobe 4, $(P)Countersxy.NELM doesn't change. It is still the inital value 1, and $(P)Countersxy read only 1 channel data.

Can we set the NELM tobe a variable?

How could we read changing channels from the above 8 channel datas?

I am confused and ask for help. Thank you so much.

With my best reguards,

Kevin