Hi Ulrik,
You wrote:
> My driver support retrieves a byte-wide array from the device and uses asyn Int32Array interface to
> send this to a waveform record with the FTVL field set to "CHAR".
But the old device support did not convert from epicsInt32 to CHAR. So the only way this could have worked is if you were packing 4 "chars" into an epicsInt32 in your driver. Is that the case? If so then Dirk's suggestion will not work, because devAsynIn32Array.c will have to assume that the epicsInt32 array really contains 1 data point per array element, not packed data. It can do the conversion from epicsInt32 to FTVL, but not in your particular case.
In your case I think the logical thing to do is to change your driver from using asynInt32 to asynOctet, which already supports waveform records.
Mark
________________________________
From: Dirk Zimoch [mailto:[email protected]]
Sent: Tue 5/15/2007 6:30 AM
To: Pedersen, UK (Ulrik)
Cc: [email protected]
Subject: Re: waveform problem with asyn 4-8
Hi Ulrik,
in my opinion it should be the responsibility of the devAsynInt32Array device
support to convert the data depending on the FTVL field. The idea with Int32 was
that registers up to 32 bits should be supported.
The documentation says:
"Note that hardware may have registers with smaller sizes, e.g. 16 bit
registers. The standard interfaces can still be used by setting the unused bits
to 0."
Thus, there is no need for 8 and 16 bit interfaces.
But that means your driver has to "blow up" the data by a factor of 4 to satisfy
the asynInt32Array interface and the device support must shrink the data to the
correct size depending on FTVL. Just to skip the check on FTVL and map longints
to 4 bytes does not do the job.
Dirk
Pedersen, UK (Ulrik) wrote:
> Hello,
>
> I've just upgraded from using asyn 4-6 to 4-8 and discovered that a
> small part of my driver support has broken. My driver support retrieves
> a byte-wide array from the device and uses asyn Int32Array interface to
> send this to a waveform record with the FTVL field set to "CHAR". The
> new version of asyn has introduced a check of this field in
> devAsynInt32Array.c initCommon and fails if the field is not set to
> "LONG" or "ULONG".
>
> As my data is only byte-wide, I don't want to fill it into a 32bit wide
> array and set FTVL to "LONG" as that would send out 4 times as much
> data. I guess the "proper" fix would be to implement int8Array and
> int16Array interfaces in devAsyn... Is anyone up for that?
>
> For now, I have just rebuild my own version of asyn with this particular
> check commented out. This way seems to work ok for now as the client is
> requesting the data type from the WF record and it seems to just "do the
> right thing" and retrieves a byte-sized array. I must admit that I don't
> fully understand if commenting out this type checking has any
> complicated implications that may break other stuff...
>
> Cheers,
> Ulrik
>
> --------------------------------------------------------------------
>
> Ulrik Pedersen phone: +44(0)1235-778580
> Software Engineer email: [email protected]
>
> Diamond Light Source Ltd.
> Rutherford Appleton Laboratory,
> Chilton, Didcot
> OxfordShire OX11 0DE
>
> --------------------------------------------------------------------
>
--
Dr. Dirk Zimoch
Computing and Controls
Paul Scherrer Institut
phone +41 56 310 5182
fax +41 56 310 4413
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