Can event structures be used w/o property nodes?

I want to know if there can be programming done using event structures but without using property nodes. My prgm has buttons and should be selected exclusively

Property Nodes really have nothing to do with Event Structures.
Property Nodes either Read from or Write to the various properties of the linked control/indicator. Event Structures react to an action from a control/indicator.
Drop an event structure and a single boolean button inside of it, configure the structure to the Value Change event for the button and hit run. The program will run, but the structure will stop the program until you click the button to run the event case, no property nodes required.
If this is not what you are referring to, provide a few more details and we'll se what we can do.
Ed
Ed Dickens - Certified LabVIEW Architect - DISTek Integration, Inc. - NI Certified Alliance Partner
Using the Abort button to stop your VI is like using a tree to stop your car. It works, but there may be consequences.

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Using LV Class Property Nodes in In-place Element structure causes the code to halt

I have some code written in LV RT 2010 that uses property nodes from a LVOOP class that I created. I am using access the property node from inside an in-place element structure. When the code reaches the property node, LabVIEW stops running. (as if the abort button was pressed). I verified this behaviour using highlight execution. When I remove the in-place structure code runs fine.
Is this is know bug in LabVIEW? Is there a CAR to resolve this created for a future release?

Bob,
I tried to reproduce the behavior you're seeing by recreating the Trigger and Trigger List classes, but I have not been able to reproduce it. Please take a look at my version of the project in the attached zip file. Take a look at Test.vi, and feel free to modify and repost it to show me how to make the problem occur. I would like to file a CAR to make sure we get the problem fixed, but I will need to be able to reliably reproduce it first.
On a similar note, you can get much better performance out of the Process Triggers VI by preallocating the list array, instead of using build array in a loop. Take a look at Process Triggers2.vi in my project. You can run Benchmark.vi to see the performance difference between the two different approaches.
Chris M
Attachments:
triggerlist test.zip ‏165 KB

Use of multiple property nodes for GUI manipulation

I have a LabVIEW 6.0.2 application where I'm using 14 different property nodes in the main loop. All of these have to do with GUI - hiding buttons when "X" isn't pressed, disabling and greying out controls if <0, popping one button on top of another depending on the mode of operation, etc, etc. While this works fine, the program is getting slow. I've noticed that using the old 2-D buttons works faster - things update faster and redraw quicker. However, more to the point, I once read that if you have to use a lot of Property Nodes like this, that you should bundle them into a sub-vi, thus replacing what would be Property Nodes with references. How does that make it faster?
Richard

Not sure if bundling them into a sub-vi by itself would make it faster. The nodes in the sub-vi would still have to access the user interface thread, and that's where the slow down comes from.
When I use any property node, I put it in a case structure and only write to it when needed. You just need to be able to detect when the value being written is changed from last loop iteration. It's useless to constantly rewrite the same value (doesn't have to be the "value" property) to the node.
Bundle them into a sub-vi and put the change detector, case structure and nodes in the sub-vi, this should help speed things up a bit. Assuming of course that the nodes are the slowdown. It may also help clean up the diagram a bit.
Ed
Ed Dickens - Certified LabVIEW Architect - DISTek Integration, Inc. - NI Certified Alliance Partner
Using the Abort button to stop your VI is like using a tree to stop your car. It works, but there may be consequences.

Calling a VI in a subpanel with parameters inside an event structure and using an abort button

Hi all,
I have a control panel with a tab control and two tabs have a sub panel in them. At runtime I load the VIs I want in to the sub panels. In the control panel event structure I want to start each of the VIs and monitor the execution state so I can abort the VI while it is running. One method I use can run the VI and the abort event will work (see example). The second method I use does not and this is what I want to do! I have many inputs to the VI I want to pass so placing the VI in the event blocks everything else and it has to wait until the VI has completed, so I cannot monitor the execution state.
I have attached an example of what I want to do.
Any help appreciated.
Martin
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Attachments:
SubPanel.lvlib ‏2 KB

Hello,
You can do this with queues.
The main vi and subpanel vi's should be based on the producer/consumer (events) and you handle the front panel events accordingly in the respective vi's.
Name the queues in obtain queue , for example the Main being MainQ, subpanels SubPanel1Q, SubPanel2Q. When you start the application, initialise the main vi and also run both of the subpanels (just to make sure that the queues are first obtained by themselves). Then you can use obtain queues to do inter vi communication.
For example if you need to send data from main to subpanel1, use obtain queue and use the name SubPanel1Q, pass the required data & command and voila. Subpanel1 vi will receive your message. You can do this anyway you want. Hope this helps.
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Can event structure detect window minimized

Can the (LV 8.5.1) event structure detect when a window is being minimized?
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Yes, you can!
The event 'Panel Resize' is the triggered event:
Ton
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Any alternate solution to using Waveform Chart Property Nodes 'ActPlot', 'Plot.Visible' for mulit-plot color problem on PDA?

Hello,
    On a waveform chart, 4 signals need to be plotted based on the status of 4 boolean inputs. Eg. if the first boolean input is true, the first signal needs
to be visible on the waveform chart; if the first boolean input is false, the first signal should not be visible on the waveform chart and so on. This can be
done on LabVIEW desktop using the Waveform Chart Property Nodes 'ActPlot', 'Plot.Visible' - a sample VI "BundleSignals_Select_Desktop.vi" is attached for
reference.
    But on PDA, since the Waveform Chart Property Nodes 'ActPlot', 'Plot.Visible' are not supported, some other method has to be used. I have done the
selection/de-selection of these signals using 'Insert', 'Delete' array functions as shown in the attached VIs "BundleSignals_PDA.zip" which works, but the
problem is that the colour of these signals do not work as desired when the selection/de-selection of these signals is done - It is required that the first
signal should always appear in White color, the second signal should always appear in Red color, the third always in Green color & the fourth always in Blue
color.
    I hope i have made myself clear of the problem. Has anyone faced this problem before & is there a solution?
Note: Version of LabVIEW that we are using: LabVIEW 8.5 Professional Development System for Windows Vista/XP/2000 and LabVIEW 8.5 PDA Module for Windows
Mobile.
Thanks & Regards,
Subhashini
Attachments:
BundleSignals_Select_Desktop1.vi ‏25 KB
BundleSignals_PDA.zip ‏26 KB

Unfortunately the only alternative to using property nodes is to set the properties manually on the development environement. The limited size of memory does limit us in terms of features for the module.
Mehak D.

Use of boolean property node in LabView 6i

I am running LabView 6i version 6.0.2.
I am using a reference to a front panel boolean control to stop the execution of a state machine in a subVI. The subVI has a property node linked to this reference. This property node shows that it is "Bool", but when I set the property node's element to "value", the value is not a boolean type. I can't figure out how to set the boolean property node's element so that I can read the state of the boolean control. How should I configure this?

The data type of the value property is a variant. It is possible to convert a variant to a boolean, but you probably don't want to do that.
The reason is that you have the mechanical action of the boolean set to "latch ...", and that means that the value property isn't very useful.
Change the mechanical action to "switch ...", then the value property will be a boolean.
Note that this means that you will probably have to reset the boolean programatically after the user clicks on it.

Use of grouped property nodes

HI,
I'd like to know if there is a way to use a property node like " value " for a group of controls without doing right click /property node /value on each control.
Thanks
Olivier

There is little reason to have many direct value property nodes in any given diagram. (I am just mention this because you explicitly mention "value"). A local variable has the same functionality but is more efficient. (of course, often you can use a wire or shift register for even cleaner code).
(see e.g. http://forums.ni.com/ni/board/message?board.id=170&message.id=153611#M153611)
There is also the shared variable, if you run one of the newer LabVIEW versions.
I am afraid that you use all these value property nodes as a poor man's substitute of "variables", breaking all dataflow in the process. Can you explain why you need so many???
(btw: another way to copy a property node would be to ctrl+right-drag an existing property node, then right-click it and "link to...(select another control)". This is not faster in your case, but is quite useful if you want to duplicate a property node that has many properties defined.)
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Is it possible to add text when using flashing button property node?

I am trying to get a text button that displays TEST to show "running"
when it flashes. I am using a property node for flashing.
At present it cycles between TEST and default color which is set in
flashing clolor options.

hi there,
use the "Strings[4]" property of the button. right click on the property node and see online doc for more information about the meanings of the 4 elements of strings[4].
Best regards
chris
CL(A)Dly bending G-Force with LabVIEW
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Where can I find docs on all the property nodes

Are all the property nodes for things like waveform charts and graphs documented somewhere. I have looked throught all the .pdf files that came with LV ( at least I think I have ) and haven't been able to find what I'm looking for.
If someone could point me to where all these are documented I would be most appreciative.
Thanks.

The LabVIEW Help describes every VI Server property and method. The easiest way to find the help for a specific property and method is to select the property or method in the Property or Invoke Node, right-click the node, and select Help for xxx from the shortcut menu, where xxx is the name of the property or method.
In LabVIEW 6.0, you can browse the property and method help by selecting Help>Contents and Index, clicking the Contents tab, and navigating to Networking in LabVIEW>Properties and Methods.
In LabVIEW 6.1, select Help>VI, Function, & How-To Help, click the Contents tab, and navigate to Programmatically Controlling VIs>VI Server Properties and Methods.
Kelly H
LabVIEW Documentation
National Instruments

Can BAPI Structure be used to generate Proxy?

Hi @ ,
I want to generate the proxy for a BAPI that i have imported the BAPI already.I don't want to use RFC but proxy based upon the BAPI structure.
REgards,

Hi
check this thread
Re: BAPI or Proxies

How can I determine whether to use an event structure or a case structure?

I'm starting a large project and need a state machine. I can't decide on whether to use a case structure or event structure. Is there an article or other information that describes criteria for selecting between the two approaches?
Thank you,
Chuck
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Hi Chuck,
Well case structures and event structures differ quite alot. Here's a link for indepth information on Event Structures, and using them in state machines: http://zone.ni.com/devzone/cda/tut/p/id/2962. Hopefuly this will help you make up your mind.
Let me know if you have any questions after reading it.
Regards,
Dominic Walker
Cardiff University
Electrical and Electronic Engineering Student

I using an event structure for an input box and also for hardware input

Hi there!
I have many input boxes and display boxes on my user interface and i have a case for it in the event structure. If the user changes the values of the input boxes, the particular event case writes this new value to the hardware. However, in the timeout section of the event structure, we read the inputs from the hardware and we set the value for its related display object. Within the timeout section i set the value for the related user interface display component, by making use of the property node value.
Furthermore, for most of the display components, i have a event case for a value change associated with it. In that event case, i check for range errors and so forth.
My assumption was that when i read the value in from the hardware and set the property node value, the user interface component's value will change and it would then trigger the event of the value changed for that component.
My assumption worked to the point of updating the component's value, however, it did not trigger the event for the value changed for this component.
Please advise me on how to achieve what i wish to.
Thanks.
Regards,

Local variables are actually much more efficient than property nodes as far as execution speed goes. Take that same VI and delete the property node and instead write to a local variable inside the loop. You'll see the speed nearly identical to writing directly to the indicator. But note that variables also cause a copy of the data to be created. So if you're just using the "Value" property, you're much better off using a local variable. But don't use both at the same time. If you are reading/writing other properties when you update/read the value, you might as well use the value property.
Sometimes you can't get around using either variables or property nodes. Initializing controls to saved values from an ini file is one example. But in this case, they are only written to once as the application starts so the performance hit is negligible.
One thing you can do is store values in a shift register as they are read and pass this through your application so the last value read can be accessed from anywhere. You can even create a cluster that runs through the shift register to hold several values in a single register. This can be expanded a bit farther to create what's called a Functional Global. This basically a subVI with a While loop that only runs once on each call. It has a shift register to store data and a Case structure to Read or Write data into the register. There's a pretty good example that ships with LabVIEW showing how these work. Open the Example finder and search for "Functional Global Communication". This example shows how to use them to pass data between two independent loops, but they work just as well in a single loop application.
One of the big advantages of these Functional Globals over the standard LabVIEW Globals and local variables is that you can add cases to manipulate the data in addition to just storing it. Also, since it's a subVI, access to the data is protected to one caller at a time whereas variables can have multiple reads and/or writes at the same time. This can cause race conditions.
Hope that helps a bit.
Ed
Ed Dickens - Certified LabVIEW Architect - DISTek Integration, Inc. - NI Certified Alliance Partner
Using the Abort button to stop your VI is like using a tree to stop your car. It works, but there may be consequences.

Can we change the property of each element of an array using property node or by other methods?

Hello all,
Can we change the property of the elements of an array. For example:
I have an array of combo-boxes. Can i have such a scenario that different combo-boxes of the array will have different items to select an item.
I am able to set the different "values" in different combo-boxes bu using "to be more specific class" property node.
But i could not set the different item list in different combo-boxes.
Please give me the solution.

Thanks a million dave!!!!!
I have learnt a very new and innovative thing...
I just wanna ask you one more question in the above context.
Can i have listbox or combo-box in a table just like in an excel sheet where we can have listbox by using "data validation" property for different cells having different list.Can i have this in labview. Because for this i have to super-impose the combo-boxes on the table and treat them separately.
We have to take those combo-box values and put in table and then store it.I have attached one VI to show the scenario.
And this is the alternative solution of the array problem which u have already given. So please suggest me between the two or any alternative solution.
Thanks,
Ankit Madaan
Attachments:
Recording _Table.vi ‏19 KB

How to use a event structure in a subVI

I am trying to use an event structure inside a subVI. The subVI has an array builder that builds arrays, and the event structure is used so that when the program is running, it allows you to change the elements of the array. It works, but when I implement it inside a subVI, it does not work properly. This is going into a subVI, because it will be a part of a much larger progrram, so it needs to be modular.

If you're using an event structure, it's not a subVI. if you're worried about modularity, you shouldn't be using the event structure.
You seem to have a fundamental misunderstanding of modularity. An event structure should be placed within a while loop. If you have a while loop within a subVI, you've handed over control of your program to the subVI. You're not modular at this point. Your top level GUI has no control. You'd have to create some asinine system of variables to pass data down to that loop to stop the loop and return to your main VI. That's not a good design decision.
Instead of looking for a way to do something broken, you should spend effort trying to understand what you actually want to accomplish. You should also spend some time learning how event structures work.
This application is small right now and it's already on the path to unreadable. That's a terrible thing to do to yourself. Break these habits now. se variables only when absolutely necessary. Use subVIs to accomplish individual tasks, not run the entire application. With event structures, use a stop button value change event to not be held hostage by the timeout. If your variable has "2" in it, you're doing something wrong. There has to be something different between the setpoints, put that in the name. If you want to make subVIs, create an icon.
But first and foremost, invest time in understanding dataflow

Can event structures be used w/o property nodes?

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