Re: monitors on array variables

["D. Peter Siddons via Tech-talk" <tech-talk at aps.anl.gov>]

Hi Michael,

   I never did understand how arrays are handled in EPICS. Do I really need two fields in the database, a value and a buffer? How does it work? If there were only one field it would make life much simpler!

In cvt_dbaddr, do I need the

paddr->pfield = (void *)(pzDDM->pspct); 

statement?

Pete.

On 3/24/20 1:08 AM, Michael Davidsaver wrote:

> On 3/23/20 10:32 AM, Siddons, David wrote:
> > Hi Mark, Michael,
> >    Adding Michaels post-all command at the end of process() and special() made things update properly.
> >       
> Excellent, so it is only a question of sorting out the arguments passed to db_post_events().
>
> > Also, replacing that command at the end of special() with scanOnce() had the same effect. I'm afraid I don't understand things deeply enough to know why the individual posts didn't work. I would offer to send the code, but it is long and complicated and I don't want to bother you with it. At least I can move forward with other implementation details still to be done. If you have any further suggestions for things to try I'd be grateful.
> >       
>
>
> From the number of alternatives commented out, I take it that this is where your having problems.
>
> >  //	db_post_events(pscal,&(pscal->runno),DBE_VALUE); 
> >  //	db_post_events(pscal,&(pscal->mca),DBE_VALUE); 
> >  //	db_post_events(pscal,&(pscal->tdc),DBE_VALUE); 
> >  //	db_post_events(pscal,&(pscal->spct),DBE_VALUE); 
> >  	db_post_events(pscal,NULL,0xf); 
> >       
> https://github.com/dpsiddons/Hera-384/blob/889be28db1ae736f3a14b44988544e55fd765fb0/Mars_DDM/zDDMApp/src/zDDMRecord.c#L769-L773
>
> Since you used it in your mails, I'll take SPCT as an example.  I think what you have here would be correct, including the `&`,
> except for the code in cvt_dbaddr()
>
> >  case zDDMRecordSPCT:{ 
> >     paddr->pfield = (void *)(pzDDM->pspct); 
> >       
> https://github.com/dpsiddons/Hera-384/blob/889be28db1ae736f3a14b44988544e55fd765fb0/Mars_DDM/zDDMApp/src/zDDMRecord.c#L255-L256
>
> Because `DBADDR::pfield` is being overwritten, it is necessary to post using the address being stored in pfield.
>
> > db_post_events(pscal, pscal->pspct, DBE_VALUE); 
> >       
> Note the absence of `&` as the address being assigned to `pfield` is the address of the allocation,
> not the address of the zDDMRecord::pspct field.
>
>
> Also, as a note.  To be archiver friendly, the usual mask is 'DBE_VALUE|DBE_ARCHIVE'.
>