Active x and event callback in Labview

I have an active x written by Aanderaa Instruments (makes
weather and hydrology sensors), it contain various methods and events to get
the next line of records from a sensory scanning unit. The connection is
through the COM1, so far i have wired it up only using the methods to get next
record level, but then I have found that sometimes it does not get the complete
record from the COM port. So to solve that I have to use an event in the active
x to check for new record available. So what I want to do is send the event
(when complete record available) to VI that uses the get next record method to
pick up the data from the COM1 port and then send the data back to the main VI
for processing, plotting and writing.
My problem is that when I connect the output from the GetNextRecord method to a
indicator that I then wire on the connector pane to be an output from this
VI get an error that there is a wire function conflict. I have tried to
explain a bit better in the attached pdf file with diagrams.
The reason why I want to export the data back in the main VI is because it runs
continuously collecting data every 2 min and I plot them on a graph and write
them to a file so it will no work to have all that done in the event callback
VI that will only run ever 2 min, then it will reset the graph the whole time
and I want continuous data plotting for 10 days of historic data records. I
also have a few other sensors that come in through a connector board that are
written o the same file.
hope somebody can give me some hints
Attachments:
labview question.pdf ‏721 KB

Duplicate post, click here for the original: http://forums.ni.com/ni/board/message?board.id=170&message.id=135639#M135639
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Event callback with active x in labview

I have an active x written by Aanderaa Instruments (makes
weather and hydrology sensors), it contain various methods and events to get
the next line of records from a sensory scanning unit. The connection is
through the COM1, so far i have wired it up only using the methods to get next
record level, but then I have found that sometimes it does not get the complete
record from the COM port. So to solve that I have to use an event in the active
x to check for new record available. So what I want to do is send the event
(when complete record available) to VI that uses the get next record method to
pick up the data from the COM1 port and then send the data back to the main VI
for processing, plotting and writing.
My problem is that when I connect the output from the GetNextRecord method to a
indicator that I then wire on the connector pane to be an output from this
VI get an error that there is a wire function conflict. I have tried to
explain a bit better in the attached pdf file with diagrams.
The reason why I want to export the data back in the main VI is because it runs
continuously collecting data every 2 min and I plot them on a graph and write
them to a file so it will no work to have all that done in the event callback
VI that will only run ever 2 min, then it will reset the graph the whole time
and I want continuous data plotting for 10 days of historic data records. I
also have a few other sensors that come in through a connector board that are
written o the same file.
hope somebody can give me some hints
Attachments:
labview question.pdf ‏721 KB

Hello!
I checked the PDF file with snippets of your code and it looks alright, no issues or comments regarding that from my side. However it is really difficult for us to troubleshoot when we don’t have the ActiveX control available and even though we had access to the control it would still be quite tricky to find the cause of the problems you are experiencing since we don’t have the hardware and so on.
I found one link only that mentioned wire conflicts when talking about COM objects and ActiveX and you can find it here:
http://digital.ni.com/public.nsf/websearch/0CED780C5D5EDCD5862569D9005AE1FA?OpenDocument
Regards,
Jimmie A.
Applications Engineer, National Instruments
Regards,
Jimmie Adolph
Systems Engineer Manager, National Instruments Northern Region
Bring Me The Horizon - Sempiternal

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Dear Fellow LabVIEW programmers:
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LabVIEW as a collection of HSM-driven active object VIs using a higher
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Configure Event Callbacks in test stand using labview

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I was going through Full OI - Configure Event Callbacks.vi in the test stand example. Can you please explain me how the vi works and what is techniwue behind it?
When i open the individual VI's in the reference, I could see more that 1 control in the front panel. But Only the user parameter is wired in the vi? Why is it so?
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When the TestStand Engine fires events, this VI specifies how your Operator Interface will respond. For example, let's examine the first event callback registered in Full OI - Configure Event Callbacks.vi , Exit Application. When the TestStand Engine receives the message to shutdown, and then finishes its neccessary shutdown procedures, it will send a message to the Operator Interface. For the Operator Interface to receive this message, it must "listen" for it. In LabVIEW, this is done by Registering an Event Callback. See the links below for details on how to implement this.
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Register Event Callback (Not in Base Package)
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National Instruments
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Executable and Register event callbacks

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akonecki wrote:
Hi,
I have been running into an issue regarding the building of an executable that has register event callbacks (specifically Test Stand Callbacks). The VI that is responsible for setting up the event registration is an asynchronous VI. During development everything works but during deployment of an executable the Callback is either not running or capturing the event from the Test Stand engine (I am looking for the end of execution event). The setup is not reporting an error, and the pathing to the callback VIs is correct. Any Ideas on this?
Does the Teststand engine not post a endexecution callback when running from a executable labview environment?
Thanks,
Andrew
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Event CallBack in TestStand - Labview OI

Hi everyone,
i am using the simple interface for labview of teststand, i have modified the interface what i like, now what i want to do is when the user press the control button to execute a sequence the system ask the user for something and depending of it answer execute or not the sequence, for this i have create a new event callback, modifying the configure event callback.vi, what i introduce in the Reg Event Callback is that when StartExecution event starts it run the callback vi that contains the question to the user.
It works well because when the user press the run sequence control button or the restart contorl button, the system ask the user. But the problem is when the user press the exit control button, the system ask too.
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I would like to select an event case in an event structure when a new date is selected in an active x contained calendar. How do I get the active x event to be seen within Labview?

Hello optobionics,
Assuming you are using LabVIEW 7.0 or 7.1, there are two shipping examples that deal with registering callback functions for ActiveX events: �ActiveX Event Callback for Excel.vi� and �ActiveX Event Callback for IE.vi�. This will give you some idea of what to do. It is actually up to the program being called through ActiveX as to whether the events are available or not. The following KnowledgeBase also discusses using callback functions.
Migrating from the ActiveX Event VIs to Using the Register Event Callback Node
If none of these suggestions help, or if I�m not correctly understanding your issue, please reply with comments or answer
s to the discussion above and any additional information that may help, and I�ll be happy to look further into it.
Have a nice day!
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Robert Mortensen
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Problem with register event callback in use of instrument control

now, i use the register event callback to register a value change of a boolean control on the front panel, and wire the cluster's ref of the instrument control parameters to the user parameter input, then create the callback vi. In the callback vi, i select the pump-control subvi, and pass the user parameter to the subvi. The problem is that, when i press the boolean control, the instrument (here is pump) can act, but immediately, the code crashes.
I use labview 8.6
Attachments:
callback vi.png ‏8 KB
register event callback.png ‏8 KB

You would wire the event registration wire that comes out of the Register for Events node into an event structure. You will need to right click on the event structure and check off "Show Dynamic Event Terminals" and it into that. Then you can create a new Event Case that uses the dynamic event. You can place your subVI in that event in whatever way you want. (Just drop the subVI in or do a Call by Reference there, or whatever.) Look in the Example Finder for "Dynamically Register for Events.vi".

Problems with ActiveX Callbacks in LabVIEW 7

Have encountered an interesting problem with ActiveX "Reg Event Callback" in LV7 (WinXP):
In a nutshell, when a lot of events fire in rapid succession, the user-interface locks up.
The events still fire, and the front panel controls update, but the front panel will not respond to clicks. Interestingly, if the block diagram is open, you can stop it and turn on execution highlighting, etc...
- I've discovered that the problem we're encountering is related to multiple events firing before the (reentrant) callback VI has finished executing from the 1st event.
- by watching the Performance data in task manager, and tracking the # of handles used by LabVIEW, I find that when this happens, the # of handles increases, b
ut never decreases until you stop the VI
- I would expect several (nearly) instantaneous events to launch multiple copies of that callback VI, and I can believe that would increase the # handles, but I would expect that LabVIEW would catchup shortly thereafter and the # handles would return to its starting count.
As an aside, using the old ActiveX event and callback method with the exact same version of the activeX control does not have this problem, events just queue up and then fire appropriately.
Anyone seen anything like this?
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Follow up question (NI guys): when will the support for the old ActiveX event stuff dry up?
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Ben Zimmer
[email protected]
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Meikle Automation

Hi Ben,
The error message warns about the use of three ActiveX Event VIs that will no longer be supported in future versions of Labview. Following version 6 of Labview, the use of ActiveX Event VIs is shifting to the use of Register Event Callback VI instead. In looking at your screenshots, I did not see any use of the older ActiveX Event VIs. If possible, try attaching the actual VI to the post and I will take a look at that.
At least in terms of support, phone support currently exists for Labview 6 and 7. With the release of Labview 8, support for Labview 6 will slowly be phased out. In this case, phone support for the ActiveX Event VIs will no longer continue as they are no longer included in the versions of Labview for
which phone support is provided. However, Discussion Forums and web-based resources would be your best venue of support for those features.
I would strongly recommend that you migrate to replacing ActiveX Event VIs to using the Register Event Callback VI. The following is a KnowledgeBase article describing the transition of ActiveX in Labview:
Migrating from the ActiveX Event VIs to Using the Register Event Callback Node
Also, are you using the Automation Open/Close VIs? These two VIs will allow acquire/release informatio nof the ActiveX object. I have attached a couple example programs that are included in Labview to help demonstrate this concept.
Hope this helps!
Kileen Cheng
Applications Engineer
National Instruments
Attachments:
ActiveX_Event_Callback_for_Excel.llb ‏944 KB
ActiveX_Event_Callback_for_IE.llb ‏972 KB

How to access new data in User Message Event Callback?

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The sequence sends a User Message to the OI to request the string array of tests to run.
But I am having great difficulty making this string array data available to the event callback VI.
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Solved!
Go to Solution.

Hi Ray,
The 'Selected Tests' array refnum is #4 in the cluster order and matches all the way through - so I think that's OK.
In the final diagram above, I can get the Selected Tests cluster from the 'User Parameter', but it is still in the form of a refnum.
My problem is a lack of understanding in how to convert this 'Selected Tests' refnum back to the original data type (a string array).
Basically I want to get the string array from the 'Selected Tests' refnum.
As you can see from above I tried to use a property node. I've also tried to 'cast' the refnum to a 'more specific class' by choosing 'Array' but it's still ends up as a refnum.
I hope you see what I mean?
Thanks,
Ronnie
TestStand 4.2.1, LabVIEW 2009, LabWindows/CVI 2009

Event Callback from a Reentrant VI Recursion Error

Greetings,
I am using Register Event Callback with an ActiveX object to respond to user mouse events. The problem is that when I run the VI (the main, calling vi) as reentrant, Labview gives an error that the "Callback.vi" is attempting to recursively call "Main.vi".
Is there a way around this problem? I intend to run two copies of "Main.vi", so reentrant execution seems necessary.
- Colin Holbrook

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Are you placing the Register Event Callback inside of the Main VI and then wiring the same Main VI to the VI Reference terminal? If so, then that explains why you are getting an error. You cannot use the Register Event Callback to call a VI within itself. If this is not the case, then please post a simple VI that demonstrates the problem.

Active x and event callback in Labview

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