Event Structure Trigger Controller

Hi Everyone. I'm working on a motion control system for a flight simulator base using Labview. My code uses a while loop with a few case structures to constantly transmit data to a second computer where it is conditioned into base motion data. Currently, these transmissions occur in real-time: I cannot input three different commands and execute them at once.
I want to be able to input multiple different values into a seperate controller and "start" them all together. An event structure seems like it would be the perfect solution to my problem, but I'm having difficulty with the program timing out or receiving the wrong inputs, which causes some diasterous effects on the machine. Any help on where I should place this event structure, how to wire the inputs to existing controls, or any helpful tips are greatly appreciated.
Attachments:
HostControler2.vi ‏78 KB

1. Your event structure must be inside a while loop to trigger on more than just a single event. http://zone.ni.com/reference/en-XX/help/371361H-01/glang/event_structure/
In your VI the event structure will only ever fire once when you click "Start 2". Then it will never fire again.
2. Every control that you want an event to fire on must be registered and handled in an event case. They can all be in the same case, as long as they are registered in there somewhere.
3. Try to keep your block diagram on a single screen, it makes it easier to follow. (Unless your screen is actually twice as high and wide as mine?)
4. Try to keep all wires visible and all data flow from left to right, wires shouldn't be going backwards or behind objects etc. That will also make it easier to follow.
5. You are already using basic state machines, you probably don't need to have a while loop in a while loop.
6. If you need different actions performed asynchronously you will likely need more than one while loop (executing asynchronously, not nested) using queues to communicate between them.
7. Do you really need to continuously transmit data or only on change?
There's more but that should give you a good start.
Troy
CLDEach snowflake in an avalanche pleads not guilty. - Stanislaw J. Lec
I haven't failed, I've found 10,000 ways that don't work - Thomas Edison
Beware of the man who won't be bothered with details. - William Feather
The greatest of faults is to be conscious of none. - Thomas Carlyle

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How to Transition to a Specific Case from an Event Structure Trigger?

Can someone help me troubleshoot my program. I've attached my VI so you can follow along with what I am describing. So here is the scenario:
I have a program that consists of four test states, stop test, request test info, and end program (cluster of 7 booleans). Each test state sends a serial command to a DUT, receives ACK packet, opens relays which disconnects the serial connection and DUT will continuously test by itself. If the user wants the end the test early, they can hit the "Stop current test" which will close the relay reestablishing serial communication, wait 10 secs for device to enumerate on the PC, and then send the serial command to stop the test. From here, the user can request test information from the DUT by hitting the "Request info" button.
So my dilemma is when I try to implement a time limit for cases 2 - 4. For case "M1-Idle", the program works flawlessly since there is no time limit. The program will send the serial command, transitions to "Open Relay" case and switch back to the "Idle" state to wait for the "Stop" command. The user has to hit stop whenever to close the relay, request info and/or continue testing.
For case 2 through 4, there is max time limit of 3 hours. This is where I am having difficulty opening the relays and then entering the timer count down case structure to start the timer. Question is, if I am using the Event Structure to trigger on a user action event (i.e. user presses "Run M2-Normal" - Menu.M 2: Value Change) it sends the command and move on to "Open relay" to break the serial connection as intended. Since the next state of "open relay" is "Idle" how can I add case selector to select "M2 - Timer" instead of "Idle" given that it was based on user selection of "Run M2" event?
Is that even possible? I tried using the feedback node on the state enum but its coming from the case state and not the event state so it doesn't enter properly into the timer state. Any help or ideas is greatly appreciated. Thanks in advanced.
Main_Working_Copy.vi is the main portion of the program.
Best regards,
Henry
Attachments:
Main.zip ‏106 KB

Hi Ofek_zeevi,
Welcome to the Support Communities!
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Why do event structures trigger duplicate events for value changed, sometimes?

In this simple VI, an event structure is used to trap a value change within a color array.
However, when you run the VI and change a color, it triggers the event structure twice. The second time the structure executes under the value change event, an impossible state exists where the structure is executing as if oldVal<>newVal, but they are in fact, equal.
I have had to write around this many times. Why?
Attachments:
doubleEventExample.vi ‏91 KB

For completeness, I reported it also in the February bug thread, so it should get noticed:
http://forums.ni.com/ni/board/message?board.id=BreakPoint&message.id=3385#M3385
LabVIEW Champion . Do more with less code and in less time .

How do i get a boolean indicator to trigger a event structure

I have two parallel loops running, and i need to use a boolean value, one that comes out from an OR gate, to trigger an event in the parallel, event structure loop. I've attached a simplified version of the loop. Is there a way to get this done? I've tried using local variables, value(signaling), etc. and they haven't worked
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Attachments:
Parallel Loop Trigger.vi ‏10 KB

Here is a revised version of your VI. I modified the mechanical actino of the stop button so it kept it's value until it was read. In addition, I added a delay to your upper loop. Without a delay it was running too fast to actually see the button press. I modifed the event in the the event structure to trigger on a value change of Boolean.
You don't really need the outer loop since it will only run a single time in all instances. On the first execution of that loop it will be sitting in the turn inner loops. Once you exit the two inner loops your outer loop will always exit. Therefore, it serves no purpose.
Your OR in the upper loop is completely uses. It serves no purpose since the result will always be equal to the value of the Stop button.
There are better ways of triggering events. a preferred method would be to use a user event and simply generate the event at the appropriate time. This has the advantage of not requiring additional controls/indicators simply to cause an event to occur.
Mark Yedinak
"Does anyone know where the love of God goes when the waves turn the minutes to hours?"
Wreck of the Edmund Fitzgerald - Gordon Lightfoot
Attachments:
Parallel Loop Trigger.vi ‏12 KB

Event structure: have one event trigger another event

I have an event structure with two events. I want the finalization of the first event to trigger the second event. Both events are triggered by a boolean value change, say "boolean 1" and "boolean 2". Can I have a local variable of boolean 2 inside event 1. By changing its value, it should trigger event 2. However, this doesn't seem to be working. (see attached example)
any help?
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Attachments:
test.vi ‏9 KB

Tim's reply is the answer you are looking for.
I would like suggest that you create a sub-VI that doesw the work in the second event you want to fire so tht rather than resorting to having one event trigger another, you can simply use the sub-VI that does the work in event_2 after the sub-VI that does the work for event_1.
If you decide to stick one event triggering another, please clearly document the sceme in BOTH events. What you want to avoid is latter deciding event_1 should be triggered by Event_2 and the next thing you know, your app hangs.
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction

Trigger Event Structure Case on Startup

Hello,
Within my project, I am controlling a linear actuator via Modbus TCP, with an event structure within a loop. I control its velocity, acceleration ... etc. It works beautifully, but I must change the values of the mentioned parameters to trigger the event cases, after startup. I would like to trigger the event on startup of the program and take the current values on the front panel.
I have heard about "Property: Value(Signaling)", but I cant seem to understand it and how to implement it..
Any guidance and help would be appreciated!
Thanks,
Danny

It won't work for you because you already have something designated for the timeout case, and you want a different event case than that to run on startup.
But, here is the explanation.
At the top left of the event structure is the timeout terminal. The number you wire in there tells how frequent the timeout case could execute. If you put a 0 constant outside of your loop and wire it into that terminal through a shift register, it will execute immediately or almost so. After the event structure, wire a -1 into the right hand shift register. Then after successive iteration, the timeout case will be disabled.
Attachments:
Example_VI_BD.png ‏12 KB

Trigger Event Structure in SubVI

Here's my goal. I have a VI that sets two analog outputs which in turn control a power supply. One output controls voltage while the other controls Current Limit. I created a VI which uses an event structure so that when the voltage or current limit is changed, the analog outputs are adjusted accordingly.
Now, I'd like to turn that into a SubVI and have it running in the background while my main VI runs. I'd like to be able to go into the subVI and change those values at certain locations within the main VI. I tried just using the subVI with register events, but it hangs because it is waiting for the subVI to finish before continuing. I tried using the Run VI methond with "wait until done" set to false, but then I don't see how to trigger my events because I can't link my mainVI to the events that need to be triggered. I can set the control using Control Value Set, but that doesn't do anything for my event structure and thus stuck again.
Maybe the event structure isn't the best way to do what I'm seeking. But I don't want to set all this up in my Main VI because it just adds too much complications and I already have the VI working by itself and just want to turn it into a subVI.
Thanks.

You could either get a reference to the SubVI and find the specific control like the attached picture, or you could pull the SubVI out of the main loop. If the SubVI is necessary for data flow, you are almost certainly going to have a hang up if you don't call it by reference.
edit - Another, probably less popular, option would be to have the subvi running in a parallel loop and have locals take data from the control loop and write to the command loop. You'd have to be careful to only have one local writer, though.
Message Edited by JeffOverton on 01-30-2008 02:39 PM
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XP SP2, LV 8.2
CLAD

How to exit event structure after a trigger occurs?

I am acquiring some analog signals. Before the trigger occurs, I would like to be able to save the setting or load the settings. I am using an event structure to do it.
My problem is I can't not exit the event structure after the analog acquisition is finished.
I am attaching the vi.
Thanks for your comment.
Attachments:
event.vi ‏53 KB

Seems you are trying to fire an event using a local variable. This will not work. Events are primarily designed to handle user interactions on the front panel. If you want to programmatically fire the stop event, you can write to a "val(sgnl)" property of the stop button.
Still, you program needs quite a bit more work than that. For example you cannot do any save or load operation before the trigger happens. Maybe you should redo the entire thing as a state machine?
LabVIEW Champion . Do more with less code and in less time .

How to trigger value change in event structure

Hii everyone, as the title, how should I trigger the value change event to pop up a message.. below is my connection..
I want to trigger the event structure to pop up the sub-vi, when the flame and led are TRUE state... I using property node but still the event structure not able to execute.. How should I connect? Thank you very much...
Solved!
Go to Solution.

There are several ways you can do it. First you have to configure your sub-vi so that it does whatever you want when it runs (in the vi properties, top most window for example) and to make sure that it closes completely when finished (when clicking the "OK" button for example).
You than need to make an asynchronous call to the sub-vi. There are several ways to do it. My favorite one is shown below. You go in the "Application control" sub-palette and select Static VI reference. I like this approach because it keeps track of the sub-vi path for you, as long as the sub-vi is in the same project. You then drag the sub-vi onto the empty square that will changes to your sub-vi icon. You then connect to an invoke node from the same sub-palette and select run VI. Set "Wait Until Done" to false and the main VI will keep running after starting the Sub vi. Set "Auto Dispose Ref" is the easiest way to go. Otherwise you have to keep track of the sub-vi reference and close it yourself when you're done.
Marc Dubois
HaroTek LLC
www.harotek.com

Use Event Structure to trigger a 1 off event

I am trying to use an event structure to trigger a 1 off event. I thought that I could check for the condition that I want to trigger the event and wire this the Val(signaling) property of a Boolean. I then created a Value Change event on this control expecting the event to trigger when the value changed from false to true. what I find is that writing to the Val Signaling property triggers the event every time not just when the value changes.
The attachment is a simple vi to try and illustrate this point using the iteration counter to try and trigger a 1 off event on the 10th iteration. The Boolean 'Once' changes from False to True on the 10th iteration but the event is triggered for every iteration. Need to run in debug
Any Help much appreciated
Ken
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Attachments:
1 off event trigger.vi ‏12 KB

One thing that I should have pointed out. I don't know what you are
going to do in your "one off" event. If it is a time consuming operation
you should not use an event but send a message to another loop and have
that loop execute the code. Otherwise your event loop will be blocked.
You can send messages to other loops in a
number of ways. Variables, Queues, Notifiers, Action Engines, etc..
Attached
is your vi modified to use a notifier. I also modified your conditional
logic. You said you wanted to have something happen only once but you
were using a less than comparison. I changed that to an equals comparison so that when i = 9 a notification is sent to a slave loop.
A message box will be displayed on the tenth iteration of the master
loop. Notice how your numeric indicator continues to increment even with
the dialog box displayed. That would not happen if the dialog box were to be displayed in the master loop.
=====================
LabVIEW 2012
Attachments:
1 off event trigger.vi ‏15 KB

Daqmx "Done" event not triggering event structure

I would like the user to be able to abort my daqmx task by pressing a button.
I am attempting to use the method in this VI:
https://decibel.ni.com/content/docs/DOC-15815
It utilizes an event structure with the daqmx Control Task VI to abort.
The example VI above works for me, on my system with my USB-6356 device, as expected.
When I attempt to incorporate the same method into my VI it does not--despite having an identical arrangement, so far as I can tell.
I believe that my problem lies with the event structure, and the dynamic registration. I am unfamiliar with this and must be using it incorrectly.
I have attached my VI, though it is cumbersome. The code which I am struggling with is in the "Acquire" case. As far as I can tell, I am doing exactly the same this in this particular case as in the example mentioned. Yet in the example, the event structure completes, or aborts, whatever you want to call it, right after the "Wait Until Done" VI executes. In my own VI, the "Wait Until Done" and "Clear Task" VIs execute, but the event structure does not register it.
Here are my specific questions: is there anything extra or special that one must do in order for the Task to properly trigger a "Done" event and pass through the event structure? At what point is the daqmx task "Done"?
thanks,
Matt
Attachments:
BoomTubeMain.vi ‏175 KB

natasftw,
My event structure is identical to theirs; what you are seeing are the two different cases that exist in the event structure. In both the example and the VI, there is a <task out>: Done and a "Dynamic Event": Value Change. In the dynamic event case, I have my abort button and relevant code--this I believe is the code you were referring to, which you thought I was missing... Regarding my multiple event structures, they should operate completely independently as they respond to different events.

Event structure in Sub VI

Hello ,
I have a developed a program which captures video and user can save images out of it. I have used .NET reference to handle the video part, and the VI is attached in this post. Now i have to make this VI as a sub VI and running this from Main VI. I tried creating event structure in Main VI which i used in sub VI , still i could not suceed. Kindly assist me in this regard
Solved!
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Attachments:
Webcam-Control-Projekt-mit-Reference-Design-2013_original.zip ‏286 KB

Hello Michael,
I have attached a model in which Main VI calls the Sub VI using Event Structure. Two events can occur in Main VI and their corresponding event Structure is called in Sub VI using Register events. When i run this VI the out put is fine some times but other times i need to trigger event many times before i can see its effect in Sub VI, my doubt is that Register events are reliable, whenever (during the execution of LV) if event occurs will surely its code in the sub Vi gets executed?
also I have put a indictor(numeric) in the SUb VI which i connect back to Main VI, when i run, i can see the result only in the sub VI not in the main VI.how to see in Main VI?
I have used the this model (which is attached ) to implement my project(which i already mentioned) . one switch for starting the video and other for recording the image. The video is getting started with out any trouble, but imgae is recorded only few times when i press the button which is for image recording, most of the time second event fails to get executed. Also there are difference in output when i run with and without "Highlight execution", why this happens, is this because of Reg events?
any more info if required let me know, i will provide.
Attachments:
Main_sub_VI.zip ‏18 KB

Event Structure Freezes Vi After Capturing The First Event

My Event structure catches the first instance of my button press but then it freezes my Vi. The reason is because of the while loop but I need the while loop to constantly read from a serial port and send data to a serial port. The vi included is stripped down to be just a while loop that does nothing. I have also tryed putting the event structure in the while loop, but the same thing is happening.
Any ideas?
Thanks,
Cason Clagg
SwRI
LabView 7.1, Windows XP

Also, put the button inside the event structure where it is acted upon, from LV help (suggest you read the entire events section of help):
When you trigger an event on a Boolean control configured with a latching mechanical action, the Boolean control does not reset to its default value until the block diagram reads the terminal on the Boolean control. You must read the terminal inside the event case for the mechanical action to work correctly. As a reminder, a note appears in the Edit Events dialog box when you configure a Value Change event on a latched Boolean control.
Refer to the Handling a Latched Stop Boolean Control in an Event Structure caveat for information about how to handle a latched Boolean control.
When you trigger an event on a Boolean control configured with a latching mechanical action, the Boolean control does not reset to its default value until the block diagram reads the terminal on the Boolean control. You must read the terminal inside the event case for the mechanical action to work correctly. As a reminder, a note appears in the Edit Events dialog box when you configure a Value Change event on a latched Boolean control.
Refer to the Handling a Latched Stop Boolean Control in an Event Structure caveat for information about how to handle a latched Boolean control.
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"It’s the questions that drive us.”
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Load defaults from file with event structure in vi

Hi All,
I've been trying to figure out how to do this but have not quite got there. Taken a look at lots of posts but can't quite find the answer to the question that i've got.
I've got a vi for controling 4 PCI cards making calls to some DLL's. I've got quite a number of controls on the FP and i use an event structure to update the values on calls to the DLL. On startup, one of the first calls that i make is initalise and that sets the cards up. I then want to load my own set of default values from a file to initalise the cards to my particular set up. While the software is running the user may change the values and wish to save a file with the new default values, or he may wish to load a different file of default values (depending on the test that he is running). I've got the Control Values:Get All [variant] and the Control Valueset [Variant] working to save all the controls values to a file and read that file in and set all the controls values. So far so good. Problem is i'm using an Event Stucture and it doesn't register that the values have changed. I could complish this by using Value(signaling) but the data from the Control Values:Get All is variant data and the Value(signaling) needs the same data type as the control. What do i do?
One thing i have thought about is to write all the values from the file to all the conrols and then have a read Value and a write Value (signaling) to trigger the events. Problem is i don't want to set this up for every control (it'll take me ages). Can i do it programitically? Is there a better way to do it?
Thanks,
Phil

You could create a boolean control/indicator and signal that value when you've updated the values on the FP.
Name it something like "update FP". The event case for that boolean will have the code to update the necessary parts of the FP.
André
Regards,
André
Using whatever version of LV the customer requires. (LV5.1-LV2012) (www.carya.nl)

How to determine the execution order of event structure

Hi everyone,
I have an event structure were it contains four events. All the four events has separate buttons to execute. Here, three events will generate numeric output, remaining one event (Finder) should find the order of those three events. For example, Three events namely A, B and C. I execute the events in the order of B, C and A. The finder event should find the order of previously executed events(B, C and A).
Thanks in advance.
Solved!
Go to Solution.

Hello Vij@y,
I could not look in to your VI because I dont have LabVIEW 2013 (I have 2010) but i tried to understand the situation you are explaining.
Please find attached image of front panel I made for your reference.
Here I generated two events sequently, no 3 first followed by no 1 and the same is displayed in sequence array. now you can use the build array function to actually add each event to this array as explained by many people in this forum.
regarding the timeout event, either you can display the sequencer array in that event or you can display it in finder event and then you can reset the sequencer in finder event (I used reset button click event to reset sequencer back to zero value)
regarding getting zero when you press finder/reset button before triggring any other event:- Is it not correct to have empty array when you have not trigger any event?
I hope I put it well and may help you to find solution.
With Regards
Miraz
Kudos is better option to thank somebody on this forum
Attachments:
Sequence.png ‏70 KB

Event Structure Trigger Controller

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