Producer Consumer & User Events with user input windows

Hello All,
I am planning to build Labview code using the Producer Consumer & User events pattern, the application needs multiple user input windows for things like personal data, feature selection etc, there could be around 15 or 20 distincts screen/panels required.
The main question from me is... Is there a best practive approach to navigating/loading from one window to another etc, and also providing a way to to retrun to the previous window.
Also I may need need to be running some slow logging and control hardware in the background while navigating some of the screens, this seems like the producer consumer vi will be running in the background while the user input causes a load/display window event.
A simple Producer Consumer multiple winjdoow example would be very welcome. Thanks.
Regards Chris

I will second Mike's suggestion to use a central VI with subpanel(s). It is usually less confusing than multiple windows. Typically, the selection/navigation mechanism is on the left of the main panel, global info (like help) on the right, and the subpanel(s) in the center.
The advantage of subpanels/subVIs is that you can launch your subVIs and keep them active in the background, even though they are not being used. This means they will keep their state information and load into the subpanel almost instantaneously the next time you need them. For a short tutorial on subpanels, check out this link. Scroll down to the fourth reply for working code. The original code posted is broken.
Communication between your VIs or loops is typically done with either queues or event structures. State information in each should be shift registers in the respective VIs. If you have the time, I would highly recommend you learn how to use LabVIEW classes. The command pattern is tailor made for this kind of application.
Finally, avoid global data if you can. Global data is anything that you can get to from anywhere (globals, functional globals, etc.). Use of these can speed your development, but can also lead to sloppy design which will cause you major problems later. If you really need globally available data, use a data value reference. It is unnamed and requires a reference, which tends to enforce better programming practice. Yes, there are instances where you truly need globally available, named data, but they are fairly rare. You should only use them if you are experienced and really know what you are doing.
This account is no longer active. Contact ShadesOfGray for current posts and information.

Similar Messages

Producer/Consumer Design Pattern with Classes

I'm starting a new project which involves acquiring data from various pieces of equipment using a GPIB port. I thought this would be a good time to start using Classes. I created a GPIB class which contains member data of: Address, Open State, Error; with member vis such as Set Address, Get Address, Open, Close...general actions that all GPIB devices need to do. I then created a child class for a specific instrument (Agilent N1912 Power Meter for this example) which inherits from the GPIB class but also adds member data such as Channel A power and Channel B power and the associated Member Functions to obtain the data from the hardware. This went fine and I created a Test vi for verfication utilizing a typical Event Structure architecture.
However, in other applications (without classes) I typically use the Producer/Consumer Design Pattern with Event Structure so that the main loop is not delayed by any hardware interaction. My queue data is a cluster of an "action" enum and a variant to pass data. Is it OK to use this pattern with classes? I created a vi and it works fine and attached is a png (of 1 case) of it.
Are there any problems doing it this way?
Jason

JTerosky wrote:
I'm starting a new project which involves acquiring data from various pieces of equipment using a GPIB port. I thought this would be a good time to start using Classes. I created a GPIB class which contains member data of: Address, Open State, Error; with member vis such as Set Address, Get Address, Open, Close...general actions that all GPIB devices need to do. I then created a child class for a specific instrument (Agilent N1912 Power Meter for this example) which inherits from the GPIB class but also adds member data such as Channel A power and Channel B power and the associated Member Functions to obtain the data from the hardware. This went fine and I created a Test vi for verfication utilizing a typical Event Structure architecture.
However, in other applications (without classes) I typically use the Producer/Consumer Design Pattern with Event Structure so that the main loop is not delayed by any hardware interaction. My queue data is a cluster of an "action" enum and a variant to pass data. Is it OK to use this pattern with classes? I created a vi and it works fine and attached is a png (of 1 case) of it.
Are there any problems doing it this way?
Including the error cluster as part of the private data is something I have never seen done and ... well I'll have to think about that one.
Ben
Ben Rayner
I am currently active on.. MainStream Preppers
Rayner's Ridge is under construction

Trigger event with user event

Hello,
I'm trying to trigger my event structure with an user event when my signal reaches a certain value.
the ultimate goal will be to send a message trough queue to my consumer. for now I'm just trying to prove functionality.
currently the event is always triggered once it's set of once and it wont stop.
Here is what it looks like.
thanks in advance
Attachments:
labview help.png ‏206 KB
Trigger Send alarm practice-ev.vi ‏75 KB
user_event_trig2.vi ‏13 KB

Erik08085 wrote:
Hello,
I'm trying to trigger my event structure with an user event when my signal reaches a certain value.
the ultimate goal will be to send a message trough queue to my consumer. for now I'm just trying to prove functionality.
currently the event is always triggered once it's set of once and it wont stop.
Here is what it looks like.
thanks in advance
i think a boolean crossing pt by pt with direction set to false-true, that will take care if your value swings in and out of your ranges
as mentioned, put the event structure in it's own loop....no point in having a timeout with an empty case

Responding to two user events with same name

LV 2013, Win 7, & LVRT 2013, PharLap OS
I have a situation where I create an ARRAY of User Events, one for each "domain" .
A "domain" is an area of DAQ: there is a SCXI domain, a CDAQ domain, an EtherCAT domain, several domains dealing with TCP instruments etc., about 25 domains all told. The name of the event is "New Channels This Domain".
When a new configuration comes to the PXI from the host, I sort out the channels by their domain and generate a user event for whichever domains have channels that have changed: more channels, fewer channels, differences. If a domain has no channels that have changed, I do not generate an event for it.
There is a handler for each domain: in that handler, I pick out the event for this domain from the array, and register to receive it. I have an event structure that responds to the NEW CHANNELS THIS DOMAIN event. Since it is an array, then no matter which domain I select, the name of the array is "New Channels This Domain".
All this works fine.
Now I have a situation where it makes sense to have one handler for TWO domains.
I can pick out TWO elements of the array just fine, and register them both. (See attached pic) But now, in the EDIT EVENTS FOR THIS CASE list, I have TWO events called "New Channels This Domain". I can select one for one case, and the other for the other case and it seems to work.
--- Is there any heartache ahead with this scheme?
--- If I change the events in the clusters before, is it going to confuse LabVIEW?
--- Is there something I can do to change the name of the event after I pick it out of the array?
--- Is there something I SHOULD do at that point?
Like I said, it seems to work, but I'm leery of it staying that way - I've had event structures disturbed before (LV2010) when changing cluster order.
Steve Bird
Culverson Software - Elegant software that is a pleasure to use.
Culverson.com
Blog for (mostly LabVIEW) programmers: Tips And Tricks

CoastalMaineBird wrote:
Thanks, Greg for that link. I gave kudos to the idea of the COERCE TO TYPE function, and it seems like it would do the trick, but as of LV2014 it's still not on the palette.
My question still remains: is it necessary? Will the event structure remember that it's supposed to use the SECOND event named "X", through all edits and recompiles? My guess is no, but I'll listen to alternative stories.
I've been using the Coerce to type for this and enums in versions 2011 through 2014 since learning about it. I've seen no issue using it in these cases. I'm guessing it doesn't behave in an expected way for extreame uses which is why NI doesn't release it yet.
As for would it always know to go to the second event if they are named the same? My guess is yes. They maybe named the same but they have different references. I would think it would be just like having two controls with the same label. You should never do this, but if you did, and made a local variables on one and wrote to it, it would always write to the correct control. It would never write to the different control with the same name. Now even if this is the case it could be confusing to a developer looking at the code, which is why I strongly suggest having unique names. But if you don't I suspect every thing would work fine, just have a bold comment or something explaining what each case actually is handling.
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Dynamic user events freeze user interface

Hi all,
I am having problem with dynamic user events.
Dynamic user event is registered to the event structure, and many dynamic user events come in very fast, about every 30 ms. It freezes up the user interface, no response to mouse and keyboard, even after all user events finish execution.
Any idea or work around?
Thanks for any help.
Anne

Hi Anne,
> Dynamic user event is registered to the event structure, and many dynamic user events come in very fast, about every 30 ms.
The 30ms rate is not unreasonably fast as long as the processing for the event(s) can be completed in less than 30ms.
What tasks are you doing in the User Event?
For tasks that may take time to complete (like logging) you could queue up the data and send it to a consumer loop.
> It freezes up the user interface, no response to mouse and keyboard, even after all user events finish execution.
My *guess* here is that you got stuck in an event that never completed.
steve
Help the forum when you get help. Click the "Solution?" icon on the reply that answers your
question. Give "Kudos" to replies that help.

Best way to link user form with user table

Hi all.
What is the best way to link an user form with a user table (with all of the functions, add, update...)? I have created a simple form, and the question is next:
depending the type object of the user table (document, master...) i have facilities to imlement the basic operations in the form? if i create an UDO i have the functions but i want to use the form that i created with a screen painter.
Thanks.

Hi again i want add a new comment please.
If i want do all functions (add,update...) of my form in my user table, and i want my user table is a <b>type document</b>? how can add new lines in my user table with objet <b>type document</b>? because when i make the instance i nedd to say what type of document is (item,order...) and when i do an add(), not add() in my user table. In what moment or how can assign that the add,update functions... affect in my table?
Thanks again.

New user coloumn with user variable input

Hi,
I want a user defined coloumn in a new Query for Report and also it should prompt for user defined values.
Case scenario.
In a report for stock status ( Qty, rate , Total etc.) i need a new column " Forex Rate" which should prompt user to put exchange value manually as on the date of running this report anytime i.e this new column has variable input.
Since the items are purchased from various sources, the report has to display the value in respective purchase currency. The value on report generation date is based on input of exhange rate as explained. This should prompt before running the report.
I just need the query part for creation of such column and user prompt. Will integrate that into rest of query.
Thanks,

Hi,
Do you have any UDF defined already?
Thanks,
Gordon

Programatically Check if the logged in user matches with user in a list item

Hi All,
I have a custom list with 1) title column 2) People column.
I simple need to check if the logged in user = user in the column 2, and if yes fill a List<> with column 1 value.
But when comparing, the value in list item is in different format than what we get by user.ToString()
Following is what I tried:
SPUser user = oWeb.CurrentUser;
List<String> usergrps = new List<String>();
foreach (SPListItem itemA in GrpSubsItems)
if (itemA["SubscribedBy"].ToString() == user.ToString())
usergrps.Add(itemA["Group"].ToString());
itemA["SubscribedBy"].ToString() gives = 10;#Some Name
where as user.ToString() gives = i:0#.w|domain\user
Kindly guide if my approach is not correct. Thanks.
Regards, Nayan

Hi Nayan,
Please modify the code like below:
SPUser user = oWeb.CurrentUser;
List<string> usergrps = new List<string>();
foreach (SPListItem itemA in GrpSubsItems)
string userName = itemA["SubscribedBy"] as string;
SPFieldUserValue userA = new SPFieldUserValue(itemA.ParentList.ParentWeb, userName);
if (userA.LoginName==user.LoginName)
usergrps.Add(itemA["Group"].ToString());
More information:
http://ethan-deng.blogspot.com/2013/03/get-spuser-from-user-column-there-are.html
Best Regards,
Dennis Guo
TechNet Community Support
Please remember to mark the replies as answers if they help, and unmark the answers if they provide no help. If you have feedback for TechNet Support, contact
[email protected]

Handling User Events in sub panel vis and main vis with same Event reference Number.

Hi All, Iam trying to work to handle events in both subpanel vi and main vi.
I have a main program, and 2 sub vi. I will load the sub VI in 2 sub panels in main vi. Each sub pael vi has controls on it.
I have created 2 User events for 2 sub panels vi. One user event consits of a Cluster with 2 Booleans (x & Y) and Other User Event consists of cluster of 2 unsigned 8 Numbers (a & b). These are created and registered in the main Vi and event register refnum is passed to the subpanel vi from the main panel vi.
I have Event structure in main panel and sub panel vis.
In one sub panel vi, When the value of one boolean(i.e. X) in the clusters changes, the Events structure in sub panel vi should perform some operation in sub panel vi only. When the value of other boolean (i.e. Y) changes it should perform some operation in main vi. I will try to Generate user event with the x value and Y value changed based on the control clicks in the sub panel vi.
The OTher panel vi should behave in the smae way when the a & b value changes.
The "Generate User Event" is working fine some times and sometimes there in no event triggered in the sub panel vi or main vi.
Please let me know what is the problem Ramesh.

There is a lot of talking, but not much understanding. It'd be better if you posted some example VI's of what you are trying to do so that the words will make sense.
One thing I can tell you is that you don't want to have two event structures handle the same event reference number. You want to have two event registrations with each one going to its own event structure.

Input and output on same device, producer/consumer structure

Hello interested people,
I have a question about using the same device for both digital inputs
and outputs. I have written a simple program of one while loop
that continuously polls the device, processes, and requests. I
have addressed the device using two DAQmx Asst. and I have attached
them with their error in/out cluster terminals to provide data flow and
eliminate the chance of addressing the devices at the same time (which
produces an error). Now I want to change this program structure
to a producer/consumer loop foundation with state machine.
In this design, I will have the DI in the producer loop and the DO in
the consumer loop, under one of the states. I can't simply
connect the error in/out ports in this configuration, so my question is
how to avoid the error caused by addressing the same device
simultaneously with two different tasks (input and output)? I
have attached two VI's, the "One Loop" vi is the original configuration
(simplified), and the Producer-Consumer vi is a NONSENSICAL program
that simply represents the desired configuration. (I don't need
any comments on the programming of this vi, it is only an example for
illustration of the problem).
I am thinking about bundling the input data and the error cluster, both
from the PXI 6528 DI, into one cluster, queueing that up, and
unbundling the de-queued elements for some kind of data flow between
the producer loop and the "Request" state of the consumer loop.
Is this the right approach, or am I barking up the wrong tree?
Thanks
Attachments:
One Loop DO DI.vi ‏102 KB
Producer-Consumer DI-DO.vi ‏106 KB

Hello,
It sounds to me like you really have two modes:
1. user interface actions determine execution
2. user interface is locked, and execution is automated.
I think it would make sense to use the producer consumer for an architecture. Basically you would do the following:
1. program the producer to handle the user interface as you normally would.
2. provide one additional event case in the producer which would be your "automated handling" case. In that case, you could put a state machine which could run until whatever conditions were met to put your program back in "user interface mode".
Keep in mind that you can use custom USER EVENTS to programmatically generate events ie. you can trigger the start of your "automated handling" form anywhere in your code at virtually any time.
I think this would allow you to take advantage of the producer consumer architecture in its intended spirit, while integrating an automated routine.
I hope this helps!
Best Regards,
JLS
Best,
JLS
Sixclear

Register event in producer consumer design pattern

Hello wire workers,
I am fairly green when it comes to dynamic event registration, so my understanding of it is probably quite flawed, but what I have implemented seems to work fine.
Assuming a fairly typical queued producer/consumer state machine architecture.
Up till now, I have done the dynamic event registration outside (i.e. to the left of) the UI loop, so all events get registered before the UI loop starts to run.
My question is:
How can I register events from inside one of the consumer loops? I cannot wire it...
Maybe an example will make my scenario more clear.
I have a DAQ loop (queued state machine). In the init state of this loop I want to register a digital input such that changes on a line are handled by my main event structure (in the totally separate UI loop). Is this possible?
I look forward to hearing positive answers
nrp
CLA

The best way to send data from the Consumer Loop to the Producer Loop is through User Events. What you will want to do is create a User Event whose data type is the registered DAQmx event refnum. Then when you register the DAQmx event in the Consumer Loop, fire the User Event with that new refnum and update the registration in the Producer Loop. That's probably hard to wrap your head around in words, so I'll attach a dummy example and pic below. Hope this helps!
VI Saved in LV85.
Message Edited by Jarrod S. on 04-21-2008 12:54 PM
Jarrod S.
National Instruments
Attachments:
DAQmx Event.vi ‏30 KB
DAQmx Event Pic.PNG ‏38 KB

Updating data in User Event doesn't propogate to uses of the User Event type

So I have a user event which is seeded with a cluster in which there are a few typedefs. Now, as you might expect, I have to pass the user event to different VIs so that they can trigger the events which are interpretted by a main vi. Pretty simple and all is happy. There's one rub though: one of my vis which is passed the user event is called by reference. The call by reference vi requires a certain vi pattern when you create the reference for the vi (namely, a strictly typed vi reference), which includes the user event type. Now, sometimes, I update the typedefs in the data type of the user event. This means that user event type changes. Now, what's maybe not too surprising, is that either the user event type doesn't update with the type def or that the type specifier vi constant doesn't update with the change in user event type. This means that every time I have to go back and create a type specifier based on the updated pattern for the vi which takes the user event as an input.
Is there a way for labview to automatically do this? One way to fix it, I'm sure, is to change the user event input into the vi I call by reference to a variant. Then inside the vi I call, to type cast the variant with the output of a Create User Event vi that has been seeded with the appropriate cluster of typdefs. But that seems pretty silly (like, why not just make EVERYTHING a variant). Any ideas?
- Chris

Take a static VI reference (from the app control palette), drag your subVI into it, right click it and make it strict and wire it into the type input for the Open VI Reference primitive. Now it should always update.
Two more advantages you get from this is that now the VI is in memory, so it will automatically be included in your build and that you can use the VI Name (or VI Path) property from the static reference to get the name for the Open VI Reference primitive and it will always work correctly.
Try to take over the world!

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.

How to use postlv user event in labview

Hi sir
I am sending data labwindow cvi dll call to labview,for that we need postlv user event.please any one knows to use postlv user evenet in labview.
Below will be the structureand i need to update in labview .
typedef struct
unsigned
uDSPIO,
// uDAQMode,
// bControllerActive,
bShutDown,
bPowerOn,
bPowerHi,
bPowerFault,
bSGIdle,
bSGHold,
uBitsIn,
uBitsOut,
uCycleCount,
uCycResidue,
uBlockCount,
uLogChannels,
uCurrentMode,
uAsigndPhysCh[LOG_CHANNELS];
float
fSetPoint,
fDAQRate,
fRange[LOG_CHANNELS],
fReadout[LOG_CHANNELS],
fMax[LOG_CHANNELS],
fMin[LOG_CHANNELS];
char
sChID[LOG_CHANNELS][32],
sChUnits[LOG_CHANNELS][16];
CTRL_CHANNEL_STATUS;
Attachments:
GDSCallback.vi ‏12 KB

AThe fixed size arrays in your structure are inlined byt the C compiler. This means they are not an array pointer (and definitely never a LabVIEW array handle) but rather LOG_CHANNELS amount of unsigned ints and floats directly embedded in the structure. In LabVIEW terms this is most easily represented as a cluster with LOG_CHANNELS elements inside the main cluster.
So basically your uAsigndPhysCh needs to be a cluster with LOG_CHANNELS elements of unsigned ints and fRange, fReadout, fMax and fin are clusters with LOG_CHANNELS single precision float values, and then sChID is a cluster with 32 * LOG_CHANNELS chars and sChUnits one with 16 * LOG_CHANNELS chars.
However I would personally rethink this strategy. This huge cluster monster is passed into PostLVUserEvent() each time and copied into the event data on every event, causing quite a bit of overhead that way. Is it really necessary to post all this data every time?
Also you have commented out uDAQMode and bControllerActive in your C structure but included it in the LabVIEW cluster which will certainly throw off your data. Last but not least the b prefix would probably indicate that you are only using that element as a boolean value, so why not consider to use bit fields there? In LabVIEW you can easily seperate those bitfields by either translating the resulting uInt32 into a boolean array or even more efficiently use boolean logic to detect the bits.
And in order to let LabVIEW react on a user event you have to create that user event with the correct datatype (your cluster monster) and then pass the user event refnum to your DLL. This DLL then calls PostLVUserEvent() with the user event refnum as first parameter and a pointer to a data structure that matches the LabVIEW user event datatype EXACTLY whenever it wants to post an event to LabVIEW. The user event is also registered in an event structure in LabVIEW which will then get triggered everytime your DLL posts an event by correctly calling PostLVUserEvent().
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

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.
How can I do it? Some example?
I am working with Create user event, generate user event and destroy user event but I don't know how it works.
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 .

Producer Consumer & User Events with user input windows

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