Experimental Physics and
Industrial Control System

"Mark Rivers" <[email protected]> · Tue, 15 May 2007 07:41:00 -0500

Hi,

I agree with Dirk's comment, devAsynInt32Array should be changed to convert from epicsInt32 to FTVL where that makes sense.  I made the change to check FTVL because there was no conversion being done, and the existing code could crash if FTVL was smaller than 32 bits.

But in this particular case Ulrik, why aren't you using the asynOctet interface, rather than asynInt32?  There is already support for waveform records with asynOctet in devAsynOctet.c

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

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System