Experimental Physics and
Industrial Control System

Jörn Dreyer via Tech-talk <tech-talk at aps.anl.gov> · Wed, 25 Oct 2023 06:35:51 +0200

Hi Mark,

thanks for the answer.Unfortunately I was not able to figure out how this could solve my problem.
This clas stakes an NTNDArray and can convert it into an NDArray (toArray). One can also put an NDArray into it, but not retrieve an NTNDArray from it
(fromArray). But to make use of it I firs would need to get a handle to the NTNDArray that my PvaClientChannelPtr is connected to.
This class has 4 functions to retrieve data (getDouble, getDoubleArray, getString and getStringArray). There is no way to retrieve an NTNDArray this way.
I thought that PvaClientChannel would take care of the conversion internally but that seems not to be the case. So probably I have to stick with the old NDStdArray.

I am working on a client program that is making use of pvAccess and the qeFramework to retrieve and display data.

Am Dienstag, 24. Oktober 2023, 14:18:01 CEST schrieb Mark Rivers:
> Hi Jörn,
> 
> You might want to take a look at the code here which converts between NDArrays and NTNDArrays.
> 
> https://github.com/areaDetector/ADCore/blob/master/ADApp/ntndArrayConverterSrc/ntndArrayConverter.cpp
> 
> Mark
> 
> ________________________________
> From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Jörn Dreyer via Tech-talk <tech-talk at aps.anl.gov>
> Sent: Tuesday, October 24, 2023 7:04 AM
> To: tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
> Subject: Strange error from pvAccess
> 
> Hello,
> 
> I am using pvAccess to read image data from a NDPluginPVA in areaDetector.
> When I do the following lines in my program:
> 
> PvaClientChannelPtr channel = pva->channel((m_ImagePrefix + *imgDataPV).toStdString().c_str(), m_AccessMethod->toStdString().c_str(), 2.0);
> epics::pvData::shared_vector<const double> array = channel->getDoubleArray();
> 
> I get an error:
> Error: PvaClientData::getDoubleArray() did not find a scalarArray field
> 
> m_AccessMethod->toStdString().c_str() returns "pva".
> If I use the same code with channel access it works.
> Do I have to pass some special string to getDoubleArray in case of NDPluginPVA?
> 
> 
> Regards,
> 
> Jörn
> 
> 
> 
> 
> 

-- 
Dr. Jörn Dreyer
HIBEF DAQ + Controls
Institut für Strahlenpysik
Abt. FWKX
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System