Re: PV Access

[Ben Franksen via Tech-talk <tech-talk at aps.anl.gov>]

Am 26.03.20 um 09:49 schrieb Kivel Niko (PSI):
> In the doc, this example is given:
>
> {calc: {expr:"A*B", args:[{db:"record.VAL"}, 1.5], prec:3}}
>
> which uses the link type 'calc', which must be a valid link type
> according to the documentation. However, I receive the same error.

This is consistent. we already established that {db:"record.VAL"} is not
a valid JSON link so according to the docs, the whole "calc" is neither.

> Whenever I use anything author than 'pva'.
>
> Also, if (and it doesn't sound that strange)
> "{db:"${SYS}:constFloatPi"}" is as valid PV, so is
> "{pva:"${SYS}:constFloatPi"}", which works perfectly fine.

I guess it's called "extensible link types" for a reason ;-)

So in base-7.0 there has to be a module that extends the JSON link
syntax to handle "pva" links. But there is no extension that handles
"db". You may of course question why this is so and I can't answer that,
except that it seems to be a feature that is currently not supported.

Cheers
Ben

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