Re: Waveform to single ai (again)

["Dr. Simon Friederich via Tech-talk" <tech-talk at aps.anl.gov>]

Dear Erico,

Thank you very much for the reply and the explanation concerning the MALM field.

I am no programming expert: Does it matter (concerning server/network resources?), if I create 128 more or less empty arrays? Or is NELM the important field that I can set to 1?

Best regards
Simon

Am 28.04.2025 um 17:59 schrieb Érico Nogueira Rolim:

> Hi Simon!
>
> I'm responding inline.
>
> On 28/04/2025 11:54, Dr. Simon Friederich via Tech-talk wrote:
> > Dear EPICS-Community,
> >
> > I have a 128 channel power supply for magnets.
> > Every 10 seconds a waveform record reads the measured voltages and
> > currents for all channels (transmitted as one string from the device):
> > Pattern send by device = U0, I0, U1, I1, U2, I2,..., U127, I127
> >
> >     record(waveform, "$(WEDLKI)imem_get")
> >     {
> >       field(DESC, "Read current of all channels 0-127")
> >       field(DTYP, "stream")
> >       field(INP,  "@wedlkiste.proto getmemarea $(PORT)")
> >       field(SCAN, "10 second")
> >       field(NELM, "256")
> >       field(FTVL, "DOUBLE")
> >       field(PREC, "7")
> >     }
> >
> >
> > Now I want to put/assign these values to single ai-records for the
> > different magnets, i.e. in my substition file I have the channel
> > number as macro (+Prefix,+Subprefix,etc.):
> > channel = $(CH) = 0, 1, 2, ..., 127
> >
> > I now need to extract
> >     Index_voltage = 2*$(CH)
> >     Index_current = 2*$(CH) + 1
> >
> >
> > I am aware of array filters, e.g. $(WEDLKI)imem_get.VAL[INDEX], which
> > would fit my needs, but I don't know how to calculate the INDEX for this.
> >
> >     record (ai, "$(P)$(R)i_get_ai")
> >     {
> >         field(DESC, "Extr curr for each channel")
> >         field(INP,  "$(WEDLKI)imem_get.[$(2*CH+1)] CP")  #
> > unfortunately that does not work
> >         field(EGU,  "A")
> >         field(PREC, "7")
> >     }
> >       
> Maybe you could try computing the string using sCalcout? Though I think
> the solution with subArray below is better.
>
>
> > I could calculate this by hand and enter the INDEX via Macro, but I'd
> > like to keep my substition file simple:
> > file ./db/debug_wedlerchannels.db {
> >   pattern
> >   {CH, P, R, INDEX} # not desired to calculate INDEX by hand
> >   { 0, wed:, c0:, 1}
> >   { 1, wed:, c1:, 3}
> >   ...
> >   { 6, wed:, c6:, 13}
> >   { 7, wed:, c7:, 15}
> >   ...
> >   { 13, wed:, c13:, 27}
> >   { 14, wed:, c14:, 29}
> >   ....
> > }
> >
> > Do you have a suggestion for me how to solve this?
> >
> > I've also tried a single element subarray and calculated INDX via a
> > calc record. But unfortunately the single values do only refer to the
> > first value (index = 0) and are not updated although I've added the
> > "CP" flag.
> >
> >     record(calcout, "$(P)$(R)__calci_INDX")
> >     {
> >         field(DESC, "Calcuate the index for the subArray")
> >         field(INPA, "$(P)$(R)i_get CP")
> >         field(CALC, "(2*$(CH))+1")
> >         field(OUT,  "$(P)$(R)i_get.INDX NPP") # works, or at least
> > caget shows that i_get.INDX is correct
> >         field(DISP, 1)
> >     }
> >
> >     record (subArray, "$(P)$(R)i_get")
> >     {
> >         field(DESC, "Extr curr for each channel")
> >         field(SCAN, "Passive")
> >         field(INP,  "$(WEDLKI)imem_get CP") # Process linking record
> > every time the target record processes
> >         field(FTVL, "DOUBLE")
> >         field(MALM, "1")
> >         field(NELM, "1")
> >         field(EGU,  "A")
> >         field(PREC, "7")
> >     }
> >       
> Using a subArray seems the easiest to scale.
>
> The issue you're having with subArray is that MALM needs to be at least
> big enough to fit the input array up to the index you're grabbing. I
> faced the same issue with [1], where reading the last 80 elements of a
> 160 value array required MALM=160.
>
> One thing to note with this is that your PVs will be arrays with a max
> count of MALM, so it might be interesting to you to simplify client
> interaction by adding an additional ai record reading from i_get. That
> would even allow you to use a single subArray with NELM=2, which reads
> voltage and current, and your separate ai records read from hardcoded
> indexes 0 and 1 using CA filters.
>
>
> > Some background:
> > The imem_get-PV is on the same IOC. Currently we use  EPICS R7.0.7.
> >
> > Thank you very much in advance.
> > Best regards
> > Simon
> >       
>
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