Labview class objects

In my lab we are working with a Photron Fastcam 512PCI. It is attached to a microscope and the image aquisition is run through LV. So far is has produced great results. However, there are some very time critical functions that need to be carried out at certain intervals in the VI. These functions are controlled with software provided by Photron, but we need LV to be able to access these functions. The software comes with an SDK with all the required DLLs. We have been attempting to use Call External Library nodes to access the required functions, but this is not working.
From what I understand, the class definition in the DLL is a CCameraControl class. When the camera connects an object is created containing all of the camera parameters and functions. Using this, its member functions should be accessed by calling the constructor to create a class object for example called obj1. Then a function is called as such: obj1.GetManualTriggerPosition(position). Yet it does not appear that LV has integrated the concept of class. Is there any way to have LV call these functions?

abriggs8 wrote:
In my lab we are working with a Photron Fastcam 512PCI. It is attached to a microscope and the image aquisition is run through LV. So far is has produced great results. However, there are some very time critical functions that need to be carried out at certain intervals in the VI. These functions are controlled with software provided by Photron, but we need LV to be able to access these functions. The software comes with an SDK with all the required DLLs. We have been attempting to use Call External Library nodes to access the required functions, but this is not working.
From what I understand, the class definition in the DLL is a CCameraControl class. When the camera connects an object is created containing all of the camera parameters and functions. Using this, its member functions should be accessed by calling the constructor to create a class object for example called obj1. Then a function is called as such: obj1.GetManualTriggerPosition(position). Yet it does not appear that LV has integrated the concept of class. Is there any way to have LV call these functions?
Your best bet is to create an external wrapper DLL which translates the object oriented interface of your C++ DLL into a functional interface accessible by LabVIEWs Call Library Node. The reason LabVIEW doesn't have a direct Call Object Interface Node similar to the Call Library Node is because these interfaces are compiler dependant as far as the binary compatibility is concerned. So a C++ DLL created in Borland C is likely to be troublesome to be used in a Visual C application. In fact it is bascially impossible since the created link libraries are in different object format and can't be linked together anyhow.
Another approach might be if your library exports its object oriented interface through Active X. Active X does among other things also norm the exact binary interface of an object and therefore allows LabVIEW to provide a common interface, which it has implemented since about version 5.1. I'm not a fan of Active X and never would recommend its use but if it is an option in your case you may try it out.
Rolf Kalbermatter
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

Similar Messages

How to get a LabVIEW class object to expose an invoke-node method?

Hi,
      I like the property/invoke-node "paradigm" used for interacting with "objects". Can LabVIEW-class objects expose their properties and methods this way? Can one or more LabVIEW-class objects be compiled into a library or "assembly" (or other distrubution format) that allows the property/invoke-node usage?
I've looked at (but not completely understood) "Creating LabVIEW Classes". Have also searched for related posts.
The pic below shows an invoke node wired to a class with a Public VI "VAT.Status.Hello.vi". I'd like to see VAT.Status.Hello show-up as a Method. (I just tried "Select Method", and selected "VAT.Status.Hello.vi" but dialog's "OK" button stays greyed-out.)
Cheers.
Message Edited by tbd on 03-29-2007 03:15 PM
"Inside every large program is a small program struggling to get out." (attributed to Tony Hoare)
Attachments:
VATStat.JPG ‏54 KB

Hi Aristos,
      Thanks for the reply!  It was a bit dissappointing, though.
It appears the LabVIEW-class object will be moving away from (what seems to me) a convenient object-interface presented by the invoke-node/method paradigm - which allows us to interface with a large set of "objects" (.NET, ActiveX, LabVIEW GUI, VISA Resource, ?) in a similar manner and independent of the object's origin. Being able to read the methods and parameters that appear in these nodes is also helpful for understanding diagram logic!
I do like the option of dropping a friendly "VI looking" icon on the diagram, but perhaps an optional - even default - VI-icon representation for a class-object invoke-node is feasible - so the LabVIEW class-object could be the more generic object first, but with a traditional-G representation(?)
Given the answer "We would like, someday, to support the property node"
and "in the next version of LV, wiring the LV class to the property/invoke nodes will break the wire so we'll avoid confusion in the future",
... I guess you'll break the wire in the next version, but (perhaps) allow it again - if support of the property node is ever implemented?
Regards.
P.S. For the record, huge THANKS to whoever it was that straightened-out enumerated-types (somewhere) between LV4.1 and LV6.1.  Every time I add or remove an enumeration in a typedef, I silently give thanks to the bright and thoughtful soul(s) who made this valuable tool work so well!
Hello. This is your friendly neighborhood R&D guy for LabVIEW classes.
Regarding your request about property and invoke nodes as relates to LV classes....
Short story: We would like, someday, to support the property node. We have no intention of ever supporting the invoke node.
Long story: As we were creating LV classes, we had to evaluate the right programming interface for these things. We wanted LV classes to behave as new data types in LV. A developer should be able to create a LV class, then give it to someone who doesn't even know OO programming, and that second programmer could use the new data type without learning a lot of new concepts. From this principle, we held fast to the idea that the programming interface should be subVI calls whereever possible. The invoke node is really nothing more than a VI minus the icon. If you want, you can popup on any subvi node and uncheck the option "View as Icon". This will make the node display in a way that has the terminals listed as text, like the invoke node. So, at the end of the day, the invoke node is simply a subroutine call in LV that is language dependent, as opposed to the language independent iconography of LV generally.
The property node is a slightly different story -- the functionality of a property node is actually different than an invoke node as its terminals are various subsets of the properties available, not a fixed list of parameters like the invoke node. The property node provides a nice interface for setting multiple properties in a block and only having to check a single error return. Very friendly. Our intent is to allow you to create a VI that has 5 terminals: object in, object out, error in, error out, and either a single input or a single output of your chosen type. VIs with this conpane could be marked as "properties" of the class and would show up when you wire the class wire to the property node. We would call the subVIs behind the scenes as needed to get/set the properties.
This is on the longer term roadmap because it is "syntactic sugar" -- it sweetens the programming style, but it is not necessary to program effectively. You can get the same effect by writing those same VIs and stringing them along on a block diagram "railroad track" style. We'll probably get around to it in three or four versions of LV -- there are some major user requests that impact functionality that have to get done first.
PS -- in the next version of LV, wiring the LV class to the property/invoke nodes will break the wire so we'll avoid confusion in the future of people thinking there's a way to use these nodes.
Message Edited by Aristos Queue on 04-02-2007 09:56 AM
Message Edited by tbd on 04-03-2007 12:39 PM
"Inside every large program is a small program struggling to get out." (attributed to Tony Hoare)

Labview class data read node problems

I've been noticing some odd things when i use read\write nodes on labview class objects.
It seems like at some point the link between the read node and what it's supposed to be doing gets broken - so that it reads out the 'default' value of the data than the actually written value. I have worked out how to fix it when it happens - by deselecting the correct node, and then reseleecting it - seems to refresh whatever is happening underneath - although it is a pretty annoying bug.
It seems to have started happening in the last few months when i updated to LV2011 SP1 in code that had been unchanged for at least a year. (so LV2010).
I can't quite pin down the exact circumstances because it seems a bit transitory. It seems to mostly happen after labview crashes - which seems to happen quite often in LV2011. I have a feeling it might be especially when you do class inheritance.
Anybody else noticed this behaviour? Have been wondering if I should avoid using these node read\writes, and go for the actual VIs.
JP

Hi JP,
Many thanks for your post. I have been using LabVIEW 2011 for a recent OOP project and not experience this behaviour so believe it could be an issue introduced in SP.1.
I have checked and this is not a known issue with LabVIEW 2011 SP.1. I have had a go at recreating the issue in SP.1 but have been unable. In order for me to report this as a known issue and ensure it gets rectified I need to be able to recreate the behaviour. If you are able to explain some steps to recreate the issue then this would be great. Alternatively, could you send me in a VI/project which has the issue?
If it seems to occur after a crash then I suspect the two are related and the key will be identifying what is causing LabVIEW to crash.
Best Regards.
Aaron. E
Applications Engineer Team Lead
National Instruments
ni.com/support

How to use two activex class objects in same vi

HI
I am using labview to read ECU data from INCA software .INCA providing COMTOOL API(incacom.dll). I am using ACTIVEX for communication between INCA & Labview. My problem is If I have used single activex class object I am able to read Inca version, getting the database path etc. If I have used two activex class in same vi (one to open Inca & other one is to read the folder structure) I am not getting output.I have attached snapshot for referance
Attachments:
activex1.JPG ‏114 KB
activex2.JPG ‏107 KB

It wasnt in the first two images you posted, or I couldnt see it anyway! That was the only reason.
Did you try the database block on its own, just to confirm that it is working?
Beginner? Try LabVIEW Basics
Sharing bits of code? Try Snippets or LAVA Code Capture Tool
Have you tried Quick Drop?, Visit QD Community.

Save Labview Class to file?

Hi there,
I am playing around with the new Labview classes and i am thinking working with classes is pretty cool.
But i am not able to save the objekt to a binary file load them and use this data to initialize the Object with this data.
Its no problem write the state of Class to a binary file oder flatten the state to XML.
But i got a lot of troubles load them back.

I changed the example so that it works.
Please have a look.
Attachments:
saveclassdata.zip ‏37 KB

Packed project Library Labview Class Issues

I packed my whole Labview project as a packed proj library during teststand Deployment
I am using classes in my labview project
unfortunalely by one of sub seq calls got the following error !
"Type mismatch. The LabVIEW Class does not match the class expected by the VI.
Cannot pass a base LabVIEW Class to call a method initially defined in a derived LabVIEW Class."

The error message is quite clear:
You are using inheritance where you do have methods which are not part of the parent class (as dynamic dispatch).
During the call, you pass an object of the parent class and try to call the (unknown) method of the child.
Why this is happening can only explain your code....
Norbert
CEO: What exactly is stopping us from doing this?
Expert: Geometry
Marketing Manager: Just ignore it.

Problem with combination of LabVIEW classes (dynamic dispatch), statechart module and FPGA module

SITUATION:
- I am developing a plug-in-based software with plug-ins based on LabVIEW classes which are instanced at run-time. The actual plug-in classes are derived from generic plug-in classes that define the interfaces to the instancing VI and may provide basic functionality. This means that many of the classes' methods are dynamic dispatch and methods of child classes may even call the parent method.
- Top-level plug-ins (those directly accessed by the main VI) each have a run method that drives a plug-in-specific statechart.
- The statechart of the data acquisition plug-in class (DAQ class) calls a method of the DAQ class that reads in data from a NI FPGA card and passes it on to another component via a queue.
PROBLEM:
- At higher sampling rates, an FPGA-to-host FIFO overflow occurs after some time. When I "burden" the system just by moving a Firefox browser window over the screen, the overflow is immediately triggered. I did not have this kind of problem in an older software, where I was also reading from an FPGA FIFO, but did not make use of LabVIEW classes or statecharts.
TRIED SOLUTIONS (WITHOUT SUCCESS):
- I put the statechart into a timed loop (instead of a simple while loop) which I assigned specifically to an own core (I have a quad-core processor), while I left all the other loops of my application (there are many of them) in simple while loops. The FIFO overflow still does occur, however.
QUESTION:
- Does anybody have a hint how I could tackle this problem? What could be the cause: the dynamic dispatch methods, the DAQ statechart or just the fact that I have a large number of loops? However, I can hardly change the fact that I have dynamic dispatch methods because that's the very core of my architecture...
Any hints are greatly appreciated!
Message Edited by dlanger on 06-25-2009 04:18 AM
Message Edited by dlanger on 06-25-2009 04:19 AM
Solved!
Go to Solution.

I now changed the execution priority of all the VIs involved in reading from the FPGA FIFO to "time critical priority (highest)". This seems to improve the situation very much: so far I did not get a FIFO overflow anymore, even when I move around windows on the screen. I hope it stays like this...

Problem with Dynamically accessing EJB Class objects in WL 7.0 SP1

I am trying to build a component which has the ability to instantiate and execute
an known EJB method on the fly.
I have managed to build the component but when I try and execute it I get a ClassNotFoundException.
I know that the EJB I am trying to invoke is deployed and available on the server,
as I can see it in the console, I also seen to have been able to get the remote
interface of the object, my problem occurs when I try and access the class object
so I can perform a create on the object and then execute my method
The code I have written is below:
private Object getRemoteObject(Context pCtx, String pJNDIName, String pHomeBean)
throws Exception {
     String homeCreate = "create";
     Class []homeCreateParam = { };
     Object []homeCreateParamValues = {};
try {
//This call seems to work and doesn't throw an exception
Object home = pCtx.lookup(pJNDIName);
//However this call throws a java.lang.ClassNotFoundException
Class homeBean = Class.forName(pHomeBean);
Method homeCreateMethod = homeBean.getMethod(homeCreate,homeCreateParam);
return homeCreateMethod.invoke(home, homeCreateParamValues);
} catch (NamingException ne) {
logStandardErrorMessage("The client was unable to lookup the EJBHome.
Please make sure ");
logStandardErrorMessage("that you have deployed the ejb with the JNDI
name "+pJNDIName+" on the WebLogic server ");
throw ne;
} catch (Exception e) {
logStandardErrorMessage(e.toString());
throw e;
Any advice would be really appreciated, I'm fast running out of ideas, I suspect
it has something to do with the class loader but I'm not sure how to resolve it
Regards
Jo Corless

Hello Joanne,
Congratulations! I'm very happy that you've managed to fix your problem. It's
always essential to understand how to package applications when deploying on BEA
WebLogic. Usually, by throwing everything into an EAR file solves just about all
the class loader problems. :-) Let us know if you have any further problems that
we can assist you with.
Best regards,
Ryan LeCompte
[email protected]
http://www.louisiana.edu/~rml7669
"Joanne Corless" <[email protected]> wrote:
>
>
I've fixed it!!!!!!!!
Thanks to everyone who gave me help!!!!
The class loader was the culprit which is what I suspected all along.
As soon
as I put the 2 jar files I was using into an EAR file the problem went
away!!!!!
Thanks again
Jo Corless
"Ryan LeCompte" <[email protected]> wrote:
Hello Joanne,
As Mr. Woollen mentioned, I also believe it's a problem with the class
loader.
You need to be careful how you arrange your EJBs, because WebLogic has
a specific
method in which it loads classes in an EAR, JAR, and WAR file(s). Please
refer
to http://dev2dev.bea.com/articles/musser.jsp for more information about
BEA WebLogic
class loading mechanisms and caveats. Also, try printing out the various
methods
that are available on the object that was returned to you via reflection.
For
example, use the getMethods() method, which returns an array of Method
objects
that you can subsequently cycle through and print out the various method
names.
This way you can discover if the class found/returned to you is indeed
the one
you intend to locate.
Hope this helps,
Ryan LeCompte
[email protected]
http://www.louisiana.edu/~rml7669
Rob Woollen <[email protected]> wrote:
I believe the issue is the home interface class for this EJB is not
available in the class loader which is doing the reflection.
If you do:
getClass().getClassLoader().loadClass(homeInterfaceClassName)
I suspect it will fail. Reflection still requires that the class be
loadable.
-- Rob
Joanne Corless wrote:
Hi Slava,
If I make my code look like you describe below I get a compliationerror telling
me that
home.getMethod() is not recognised (no such method)
If I change it slightly and use
Method homeCreateMethod =
home.getClass().getMethod(homeCreate,homeCreateParam);
The code will compile OK but when executed it still throws a NoSuchMethodException
Any ideas ?
Thanks for your help so far
Regards
Jo Corless
Your code should look like
Object home = pCtx.lookup(pJNDIName);
Method homeCreateMethod =
home.getMethod(homeCreate,homeCreateParam);
return homeCreateMethod.invoke(home, homeCreateParamValues);
Regards,
Slava Imeshev
"Joanne Corless" <[email protected]> wrote in message
news:[email protected]...
Hi Ryan,
I also wanted to mention that if you do a "header search" in this
particular
newsgroup
with the search query as "reflection", you will see many previousmessages
regarding
reflection and EJBs. I believe you could learn a lot from thedifficulties
that
others have faced and solved.I tried that and although there was a number of similar cases noneof them
actually
seem to fix my issue. Thanks for the suggestion though
Are the EJBs that you are trying to access accessible via your
system
classpath?
Try to avoid having them accessible via the main system classpath,and
only bundle
them in your appropriate EJB jar files (contained in an EAR file,for
example).Maybe I should have laid the problem out a little clearer.
I have a number of EJB's bundled up in a JAR file which is hot deployedto
the
server. Within this first JAR file is an EJB (SSB) component that
needs
to
be
able to invoke a known method on another EJB. This second EJB may
or
may
not be
within the first JAR file but it also will be hot deployed.
The component trying to invoke the method on the 2nd EJB has to
be
able to
create
an instance of the 2nd EJB without actually knowing anything bar
a
JNDI
Name which
is passed in at runtime.
I can get as far as doing the
Object home = pCtx.lookup(pJNDIName);
This returned a class with the name
"com.csc.edc.projects.allders.httppostoffice.postman.PostmanBean_mp8qy2_Home
Impl_WLStub"
My problem seems to occur when I try and invoke the create method
Method homeCreate = home.getClass().getMethod("create", new Class[0]);
My code throws a java.lang.NoSuchMethodException at this point so
I
am
unable
to progress to the next step of :
Object bean = homeCreate.invoke(home, null);
So I can return the instantiated bean back to the calling client.
Why am I getting the NoSuchMethodException, is is because I am gettinga
stub
back rather than the home interface and if so how do I get the truehome
interface
from the bean
Thanks in advance
Jo Corless

Converting a class object back to a .class file

Hi,
How can i convert a class object back to a .class file ? Thanks

any pointers on how to do it then ? i don't have
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How can i add custom attributes to a new Class Object using the API ?

Hello everyone,
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cod.setSuperclass(co);
cod.setSuperclassName(co.getName());
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oracle.ifs.server.S_LibraryObjectData oracle.ifs.beans.LibrarySession.DMNewSchemaObject(oracle.ifs.server.S_LibraryObjectDefinition)
oracle.ifs.beans.SchemaObject oracle.ifs.beans.LibrarySession.NewSchemaObject(oracle.ifs.beans.SchemaObjectDefinition)
oracle.ifs.beans.SchemaObject oracle.ifs.beans.LibrarySession.createSchemaObject(oracle.ifs.beans.SchemaObjectDefinition)
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Guillaume
PS : i'm using Oracle iFS 1.1.9 on NT4 SP6 and Oracle 8.1.7
null

Hi Guillaume,
you're welcome. Don't know exactly, but assume that ATTRIBUTEDATATYPE_UNKNOWN
is used to check for erronous cases only
and it shouldn't be used otherwise.
Creating your own objects could be simply done via
ClassObject ifsClassObject;
DocumentDefinition ifsDocDef = new DocumentDefinition(ifsSession);
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ifsDocDef.setClassObject(ifsClassObject);
// set attributes and content for the document...
ifsDocDef.setAttribute("MYFOO_ATTRIBUTE",....);
ifsDocDef.setContent("This is the content of my document");
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PublicObject doc = ifsSession.createPublicObject(ifsDocDef);
null

What is the advantage of using IB to create XIBs/Class Objects over coding?

Hi all,
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TIA, Michael.

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Hi all,
Can any one tel me the difference between business object and class Object....
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..Ashish

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The business objects are defined in the BOR (transaction SWO1). The have so-called "methods" like
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BusinessObject.GetDetail
BusinessObject.Change
which are implemented (usually) by BAPIs, e.g.:
Business Object = User
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User.GetDetail => BAPI_USER_GET_DETAIL
CONCLUSION: Business Object >< Class (Object)
Regards
Uwe

Why cannnot derived class pointer point to a base class object?

Hi,
Pleaseeee... explain me why cannot the derived class pointer point to a base class object.
I know that Base class pointer can point to a derived class object.
Thanks & Regards,
Vig....

Example:
class Base
{ public: void foo(); } * pBase;
class Derived : public Base
{ public: void bar(); } * pDerived;
Now, what would happen if you assign pDerived = new Base() and then call pDerived->bar()?By forbidding such an assignment, compiler prevents you from writing error-prone code.

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