Producer Consumer Subpanels, User events and DAQ

Hello All,
I am working on a Producer Consumer application and have beed looking at subpanels for user navigation. The application needs to be capable of responding to user generated events but also manage data received from attached data acquisition and control hardware. This is a 2 part question.
I need to implement about 15 screens in this application and have started integrating subpanels. I need to be able to navigate from one subpanel vi to another using subvi buttons but dont understand how to build this functionality. Can I build functionlaity so that when I click on a subpanel loaded vi's button it will load the vi referenced by that button and the original dissappears.
I have a 3 loop producer event template consisting of (1)data acquisition producer, (2) user event producer and (3) consumer loop but theres not much detail, are there any reasonable templates out there? I have seen the data- consumer and user-consumer but no mix of all 3.
Advice appreciated
Chris

I use subpanels to host my display vi's and control them dynamically. I would have a loop or vi process that manages your subpanel. You could use user events, queues or notifiers to send messages to this subpanel manager to perform the basic functions such as loading a vi into a subpanel, removing a vi from subpanel (you can remove and stop the vi or keep the vi running in the background or even make it a floating vi.) A subpanel button can create a local event which in turn could trigger a user event or message to the subpanel manager. I have attached my subpanel manager to give you some ideas...
Attachments:
Subpanel Manager.vi ‏39 KB

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Hi there,
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Attachments:
OldDesign.vi ‏41 KB
PCDesign.vi ‏42 KB
SSMDesign.vi ‏46 KB

Vaibhav wrote:
@ Harold
Thanks. Any suggestion how can I start and stop that loop in parallel with other loops? Like, if some event occurs, the loop should start execution, and keep on moving, while other events are being traced and executed.
In those examples where you had a while loop inside a case structure, that bit of code will only execute one time. It will immediately read the boolean at the start of the program, if the value was true before the porgram started, then the while loop will run. Once that while loop stops, the case structure will end. It will never execute again unless you completely stop and restart your program. If the boolean is false before the program starts, the false case will execute immediately. Nothing happens since it is empty and it is done, never to run again (unless you stop and restart your VI) You should turn the structure around. Put the case structure in the while loop. Make sure you put a small wait statement in the loop so that it doesn't run full speed eating up CPU cycles just polling the status of the boolean.
@ Ravens
Thanks for the detailed comment.
One thing I would clarify. The user will not be able to switch between the pages using the tab control. The program will direct appropriate page to the user. I kept the tabs visible just for your idea of the pages. Sorry, I didn't mention that.
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If the tabs will be hidden or disabled, you will probably be okay. I wouldn't call it a bad design. I wouldn't do it that way. But as long as you understand the possibility of problems and prevent that. Especially some time down the road when you modify the program in some other way that could lead to a problem because you forgot about the dependencies of the event structures on the state of the state machine.
Yes, I agree about only one event structure to handle all the events. But since the user will not be able to click somewhere else, other than those possible controls, I thought to keep it like this.
I thought the events are captured only if we are in that case. I think I am wrong, right? Events are captured at any time, even if the case has never executed before, or will never execute. Ok, The events will be captured, but will not be executed until in that case.
And that's the reason why I have two separate event structures, in two separate phases of the program.
Because, prior to page 6, the events will occur sequencially. The user will click somewhere, then some message will be transmitted over DataSocket, then some message may come , then again some user action and so on. But, when the user starts using page 6, there will be parallel process of user controls events and actions, and incoming messages and corresponding actions. For this, in the page 6, I need a different kind of execution. So I separated the two event structures.
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Attachments:
PCDesign[1]_BD.png ‏6 KB

Producer Consumer Parallelism Failing!

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Attachments:
cRIO_fake.vi ‏27 KB

RavensFan wrote:
Queues are meant for a one to one, or many to one relationship. Here you have a one to many which is wrong. When something is sent, only one of the three loops will get the message depending on which is ready to grab the message first.
You should have a different queue for each consumer loop.
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Unofficial Forum Rules and Guidelines - Hooovahh - LabVIEW Overlord
If 10 out of 10 experts in any field say something is bad, you should probably take their opinion seriously.
Attachments:
User Event Request Example.vi ‏17 KB

AE user event error

Have an AE which has errors:
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Write - Attempts to generate user event to write data to VI which is running (Error 1)
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Hi Battler,
I see that you've created the user events, but registering them involes the Register for Events VI, which is located in the same palette. It looks like a property node but has a satellite icon in the heading. It's very possible I'm missing something. Could you post your main and subVIs so I can take a look at them?
Pardon the messy snippet.
I have another question, too. It looks like you're closing the reference to your subVI in the init frame. Is there a reason this needs to be done?
Verne D. // LabVIEW & SignalExpress Product Support Engineer // National Instruments

Producer consumer "clean up diagram" puts consumer on top of producer

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There is a reason a lot of use do not like to use the Block Diagram Cleanup. It generally works for simple VIs. But I would not use it on my top level architecture.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
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Dynamic user event

Hello, I am a newbie regarding dynamic user events.
Basically, I want to create a user event that triggers an event structure in a subvi.
To do this, I wire up a "create new user event" and then pass the refnum to my subvi "more info" as seen below. But this piece of code get's stuck in the sub-vi and never leaves :[
here is my subvi below:
I'd greatly appreciate any help :]

To stop your main vi you will need to provide a mechanism to stop your sub vi.
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(This could be shared among other subvis).
When the (let's call it) Shutdown event is received, set your subvi while loop control terminal true.
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Force a user event

Hi,
In a point of my vi I want to force a user event in order to enter in
an event case in run time. I want to simulate an event over a
multicolumn listbox, for example, Double Click.
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Thanks very much,
ToNi.

tonitpp wrote:
Sorry, the object over I want to force an event is a button and not a multicolumn listbox. It works but.... when I force a Double Click event over that button the user can see how the button is pressed automatically and I don't want the user see it, I would like to do it transparent to the user. I use a value (signaling) property node and I associate to it a true value. Another way to do it?
The event also gets triggered if you wire a FALSE to the Signaling property. It does not matter if the value actually changes, only that the signaling property is written to trigger the event. Try it!
LabVIEW Champion . Do more with less code and in less time .

User Event

The Help surrounding User Event seems circuitous to me. I can find out how to name an event, register an event, send a event, and act when an event occurs. What I can't figure out is: what is the actual event in the examples shown? In the Programmatically Fire Events.vi example, I see a cluster of two integers attached to the Create User Event. What "event" is represented by this? A change in one integer, both? How is this a "User" event? What I need is a simple TEXT explanation that builds up a User Event step by step with numbered steps, starting with an explanation of what kinds of events can be used as User Events and building from there through the creation and registration of events to their actual use. This is a fundamental tool for modern instrumentation programming and I don't feel I'm getting the help I need.

I'm looking at Programmatically Fire Events.vi
I see that the Create User Event has some constants attached which apparently "type" the event.
I see the Register User Event which I suppose adds to a database of accessible events.
Inside an event called "Slider", I see a Generate User Event.
I am confused because the Event used in the Event Structure Case 0 is "Slider" Value Change. I can understand an event in that context: the slider moves, values change.
But then inside that event, a refnum connects to the Generate User Event this serves as a "name" but it is only code-readable so at this point, I have no idea what the name of the event within the event is.
Connected to Generate User Event is a bundle of "something" called NewVal and a 0. I suspect this means the User Event is "generated" when position has a new value (presumably the value resulting from the slider value change) and delay is 0.
The event is "generated" but I STILL don't know what that means.
In Event Structure Case 1, triggered by event Repeat switch Value change, a Generate Event with the same refnum "name" as before occurs when some calculated values are reached.
After the loop finishes, the refnum goes out and generates a new User Event with the same "name"
when position is -1 and delay is 0.
I am primarily interested in events as triggers for Cases in Event Structures. I thought User Event meant some kind of user-defined event that I could use for such a trigger. Instead, I see in this example that some other event triggers the Event Structure Case in which the User Event is "generated" and I have NO idea what happens that "event".
So, either the term "event" is used in some wildly differently context or I need more help. I have now seen the same refnum generate an "event" based on three different inputs. How is that not too confusing for a Help example?
How can I tell what help I need? This is the most confusing example I have encountered in my long history as an engineer.
Where does the generated event go? How do I use THAT event?
I just can't tell from what is provided and I can't find a tutorial or a book that describes it.

User events vs notify event

I've read a number of whitepapers on User Events and Notify/Wait on Notification. They seem quite similar to me, and I'm not sure which to use. I have (well, when I write it) a transmit/receive VI that I think will be running in a separate thread. It's supposed to listen for TCP/IP (rx) messages and "notify" (I use that generically here) a test that's waiting for this message. That test would access some Shared Variable, or user-defined data to extract/process the message. I will (possibly) then build a message (in another shared variable) response, and "notify" the tx routine that it has something to send. I (obviously) don't have all of this worked out, but I'm assuming right now that I need to open and keep open the TCP/IP socket because it' going to be a secure (https/ssl) channel. That's why I thought I would make this a separate thread. With this in mind, is User Event or notifier more suitable or even the right approach?

Based on your description I would recommend that you use queues to pass your messages through the system. Queues are similar to notifies with one major difference. With queues you can stack up multiple messages to be processed. With a notifier you only get a single message. The event structure works best for UI types events. Though you can define your own events I don't think the event structure would be the best option for your situation. However you could still use an event structure for processing your UI events.
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User event notification

How can I know when an event has occured. Like a boolean or event status that can be compared so that only if it is true I can execute another set of code ?
Abhilash S Nair
Research Assistant @ Photonic Devices and Systems lab
[ LabView professional Development System - Version 11.0 - 32-bit ]
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in that case, I have an event that tells me if an image is available from the camera. and only when an event occurs, that is if an image is available I get to save it. But when I do 2x2 scan and have to capture 3 images for each pixel, I see that it misses certain images. This doesnt happen in any particular order.
Is it nevessary to add unregister user events and destroy event after the event structure for every single pixel ?
Abhilash S Nair
Research Assistant @ Photonic Devices and Systems lab
[ LabView professional Development System - Version 11.0 - 32-bit ]
LabView Gear:
1. NI PXI-7951R & NI 5761
2. The Imaging Source USB 3.0 monochrome camera with trigger : DMK 23UM021
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Making an array of different user events refnums?

Hello all,
I have a question about dynamic user events. I have 6 different users events which I create, and would like to put into an array. (Such that I can use them in a For loop laters, taking off one event per loop and assigning it to a control of a vi) So far I haven't found a way of doing that since if I just wire the user events refnums to an array I get broken wires. (Similarly if I wire them to a build cluster structure.)
I think that you'll understand what I am trying to do if you look at my labview code in the attached vi.
In the vi I create some user events, and then wire them to the control of two vi's which will communicate to each other using these events. In the code you will see 6 Invoke Node structures where I use the "Ctrl Val.set" to pass the events to the two vi's. Obviously this is the wrong why of doing things. Since if instead of having 6 events I had 100, then I would need to put 100 Invoke Node structures on the block diagram (making it very large compared to the size of my computer screen!).
So what I would like to do, is put the user events refnums into a array, then put the one Invoke node structure into a For loop, and index the array to assign the events to the vi's programmatically.
Is there anyway of doing this? Or is there an alternative (/ better way) to what I have done?
(Baisically I have 2 vi's that run in parallel and communicate to each other using user events. I need to pass the events to both vi's, how do I do it in the minimum of mouse clicks, and minimum of screen space.)
Thank you!
Paul.
Solved!
Go to Solution.
Attachments:
CameraTempControllerRunner.vi ‏49 KB

I haven't created any new messages since the forum changed over, so I'm not sure. But check on the menu under Options on the upper right. I think there is a way to undo your choice and put it on another.
Kudo's have replaced the stars. Anything that was 4 or 5 stars is now equivalent to a Kudo. But with the old system, anything less than 5 stars was essentially a negative opinion in the ratings. So to simplify the multiple shades of gray (1 through 4 stars essentially being some degree of a negative) and to just eliminate the negative aspect altogether, the Kudo system was born.
I don't know if the "Accepted Solution" designation does anything to help the person whose solution was accepted, but having that designation helps people searching the forum because they have the same problem find the answer quicker.
Message Edited by Ravens Fan on 10-06-2008 10:15 AM

Are user events valid before the event structure executes?

If I create and register for a user event and immediately generate that event before my event structure has seen the registration refnum, is the event still guaranteed to be seen by the structure? That is, are events queued up? It works but I am wondering if I can rely on it. I am very sure that I can but I am creating some production code and want to be assured that I am not just taking advantage of a bug.
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=====================
LabVIEW 2012
Solved!
Go to Solution.

Generally, Felix's explanation is correct and the queue exists from the moment the register node executes, so the answer is that you can rely on this.
You should, however, be aware that when playing with dynamic registration you can experience some unexpected side effects, as you can see, for example, in this LAVA thread - http://lavag.org/topic/13607-dynamic-event-reregistration/
Another example would be this - http://lavag.org/topic/13970-unexpected-event-structure-non-timeout-behavior/page__view__findpost__p...
Or what happens if you split the registration refnum to more than one event structure (hint - NEVER do that).
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Producer Consumer Subpanels, User events and DAQ

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