Question regarding event structure

I made a vi that controls a stepper motor with controls such as relative angle, maximum frequency, and acceleration. I use an event structure to update the values after new ones are entered by the user. However, recently I was given the task of integrating this with a larger vi that controlled other parts for an experiment (I will refer to this as the motor control vi).
Would event structures in both vi's be necessary? If I want to have the controls and update button in the motor control vi, does this mean that the event structure should be completely eliminated from the stepper motor vi? I was advised to use local variables to store the values for relative angle, max freq, and acceleration and then pass all of it when the update button is triggered and creates an event. I have found this to be faulty. Would it be possible to have event structures in both vi's then?
Basically, now everything will be updated and passed from the main vi to a stepper motor vi that originally depended on an event structure. Does this require the event structure to be present in only one or both vi's? Thanks.

Hey, sorry for not including it before, I'll try my best to explain all the parts because I didn't want to overcomplicate things.
For the Stepper Motor vi, I have none of the DAQ drivers on my laptop at home so I excluded it in the file attached and simply put a text box in there place. The program starts after the run button is pressed, and then the acceleration, f max, and relative angle is entered. Afterwards, pressing update displays the appropriate waveform graph. Pressing "next task" (depending on the state of the use task button) will allow the user to input other values. The use task button simply indicates whether anything will be passed to the drivers or not.
The main Motor Control vi was done by another person. For my part (all on the right side), acceleration could be set to 3 different speeds and pressing the button triggers the event that sets a certain value to the local variable acceleration. When the update button is pressed on this vi, the new values for max speed, angle, and acceleration are sent to the Motor Client vi. The state of the run, stop, use task, and next task are also passed, and my current problem is how do I use the update button in this vi? Would passing its value create an event in the stepper motor vi? Or would it be much better to just send the controls without placing them in an event structure?
Attachments:
Motor Interface.vi ‏60 KB
Stepper Motor.vi ‏33 KB

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Event structures for dummies

After all the great help with data handling, I thought I would ask a question about event structures.
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"When I read about the horrors of drinking, I gave up reading"
Attachments:
event structures for idiots.vi ‏90 KB

The important thing about event structures is to use them in the right way. For example as a rule of thumb, don't put into an event handler anything that will take more than about 200 msec or so to complete. Why? Studies have shown that 200 msec is the longest delay you can generate without the user noticing the delay (obviously YMMV).
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Mike...
Certified Professional Instructor
Certified LabVIEW Architect
LabVIEW Champion
"... after all, He's not a tame lion..."
Be thinking ahead and mark your dance card for NI Week 2015 now: TS 6139 - Object Oriented First Steps

Questions from a rookie about event structures

Hello,
I am currently scheduled for Labview classes next month,
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Kaspar

To fix the CPU resource issue, you need to place a small wait statement in your loop. It will solve two problems:
Slow down the loop (you don't need to check for UI changes more that 10x/second)
It will allow other, parallel tasks a chance to run after each iteration. Without a wait, it will hog the CPU for 55ms before releasing control.
If your loop currently spins one million times a second and you would place a 1ms wait, the CPU would go from 100% to 0.1%!
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LabVIEW Champion . Do more with less code and in less time .

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Telephone:+632772-4941-43
Fax/Data: +632772-4944
URL: http://www.imiphil.com/our_location.html
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Event Structure Question

Hopefully I can explain this okay....
I'm using an event structure to control several features in my program and all have worked great. All of the events in my program are handled via boolean buttons with value changed option. I have a numeric control in my program that controls integration time. This changes when the user clicks the up or down arrow or types in a new value. This control is used and needed to changed the integration time in a couple of different event cases. However now I'd like to use this numeric control (integration time) to not only change the integration time but also trigger one of the events (in addition to the normal button that I have been using to trigger the event I need to have happen). (The value of the numeric control when changed also executes a case structure when it is changed in one of the other events.)
However when I tried to do this, I ran into some problems.  If I change the numeric control value during one of the events in which I need to use it, and after stopping the event, then another event seems to execute (based on the changing of the numeric control, this event is the same event I ultimately would like to trigger). Basically I need to stop the numeric control from executing after stopping another event when its value has been changed and only executing when I need it to. Everything I seem to be doing hasn't been working and I'm just not seeing any type of walk around. But I need to be able to use the control in various events to change the integration time and also if needed to change it and thus trigger an event (besides using a boolean button to trigger the same event).
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The attached amusing example is an architecture which will work for you. Read the documentation for details. It has two components - an event hander and a task handler. The event handler is the LabVIEW event structure. The task handler is the queue-based outer loop. If you need to add data to the tasks defined for the queue, make the queue element a cluster and add a variant to it.
As a general rule, most UI projects involve getting to the same task through different events, making this the standard design pattern for almost any UI driven program. You can separate the task handler (consumer) and the event handler (producer), but I have found that the synchronization problems are not worth it.
I posted 7.0 and 7.1 versions of the code.
This account is no longer active. Contact ShadesOfGray for current posts and information.
Attachments:
LargeGUIApplicationsInLabVIEW_70.zip ‏735 KB
LargeGUIApplicationsInLabVIEW.zip ‏711 KB

Event structure input event question

I'm using a state machine to do some data decoding stuff. The default initial state is Idle, which checks an output boolean value from a FIFO buffer. If the boolean value is True, go to the next state; otherwise, keeps waiting. See attached "idle_noEventStructure.vi" for part of the code. But this method will consume a lot of CPU usage.
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Thanks.
Attachments:
idle_noEventStructure.vi ‏7 KB
idle_eventStructure.vi ‏8 KB

MileP,
First off, in the state machine example you give "idle_noEventStructure.vi" the reason you may be experiencing poor performance (high CPU) is that your while loop is running as fast as the OS will allow sicne there is no timing implemented. You should always you a "wait" function inside the loop (see attached file). The loop should only run as fasat as you need to check the FIFO for new data.
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Attachments:
Event Registration.vi ‏17 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"?
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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.

How can i use the same front panel graph in more than one events in an event structure?

i want to display the signals from my sensorDAQ in a graph.but i have more than one event in the event structure to acquire the signal and display it in the graph.the first event is to acquire the threshold signals and its displayed in the graph as a feedback.after the first event is executed, i will call the second event,where the further signals are acuired and compared with the threshold signals from the event 1.my question is how can i use the same front panel control in more than two events in the event structure?please answer me i'm stuck.
Solved!
Go to Solution.

Hi,
I have attached here an example of doing the same using shift registers and local variables. Take a look. Shift register is always a better option than local variables.
Regards,
Nitzz
(Give kudos to good answers, Mark it as a solution if your problem is Solved)
Attachments:
Graph and shift registers.vi ‏12 KB
graph and local variables.vi ‏12 KB

New to mac and iphoto, questions about photo structure & organization

I bought a new Macbook Pro a couple of days ago and am still figuring things out. I wasn't displeased with windows...I just decided to try a mac anyway, So far, I adore it except for one thing, the pictures.
I spent hours researching whether to download and use picasa 3 for mac or iphoto. I decided on picasa....and now I've changed my mind. (Mostly because I tried to take pictures of the moon tonight, and they looked great in camera, but Picasa could only pick up a black screen whearas iphoto actually saw and defined the moon- and with the editing software on the two, the picasa auto-edit looked like a picture that was created in microsoft paint, and iphoto came out with a beautifully contrasted photo).
Now that I decided to use iphoto, I have been researching how to switch and still seem to have a lot of questions. (I've poked around numerous forums but have found conflicting answers on different sites).
1) I organize my pictures by folders with the month and year. I know iphoto organizes events, which it seems to determine based on photo similarity. Will my photo structure still appear in finder -> pictures?
2) Is it possible to stop iphoto from organizing my pictures and just trust me on what I want?
3) All of my friends and family use PCs, and there is a chance that due to financial concerns, when I eventually replace my macbook pro (far in the future) I could switch to a pc. Does iphoto make transferring pictures more difficult? (If I understand correctly, it does not change the photo file, a jpeg is still a jpeg but I want to be sure)
4) I do not want iphoto to duplicate all of the pictures already in my library....if I import from finder-users-pictures, will it simply use those, or duplicate all 150gb worth of pictures?
5) Any other tips for someone completely new to macs and iphoto?
6) This is very silly, but how do I uninstall picasa (I know how to uninstall on a windows but want to make sure I do things correctly on my mac!)
Also, just a "bonus"- regarding events vs. files I create, will iphoto create events within the program but leave my file structure in the library it imports from alone? If I use finder to go to where I store my photos, will I still see my file structure regardless of what iphoto does?(Does that make sense? I'm having a hard time trying to describe it)
I apologize if this question is foolish or misplaced- I did read many other posts but didn't see the answers I was looking for.

Your questions are neither foolish nor misplaced.
The first thing I strongly suggest is that you make a trial iPhoto Library. Import 100 or 200 pics and explore. Iphoto isn't right for everybody, and if you're going to use it you will need to rethink things a little.
1) I organize my pictures by folders with the month and year. I know iphoto organizes events, which it seems to determine based on photo similarity. Will my photo structure still appear in finder -> pictures?
A: Events are based entirely on Date and Time not on 'photo similarity' You can set the interval for what makes an Event in the iPhoto Preferences: iPhoto Menu -> Preferences -> General Pane: Autosplit into Events... And select from the drop down menu.
Will my photo structure still appear in finder -> pictures?
Yes or no, depending... iPhoto can run as a Referenced or Managed Library. In the former case, yes you files will be visible in the Finder, in the latter case they won't.
Note that Referenced or Managed refers +only to file storage+ It offers no extra functionality, it does nothing at all. App like iPhoto are your go-to app for your photos. If you use it, then you never access the photos via the Finder. Ever. It's always via iPhoto or the many, many hooks into the OS that it has.
I'll detail more on Referenced v Managed below.
2) Is it possible to stop iphoto from organizing my pictures and just trust me on what I want?
I'm not sure what you mean by this. Iphoto does basic date and time organisation by default. You can change it, you can change the location of the photos in Events, merge them and then using the other tools available - Albums, Smart Albums, Faces, Places etc you can organise your photos whatever way you want.
But what do you mean by pictures. There is a distinction between Photos - the image of your child holding his dog - and files: A Jpeg is just a file. Iphoto is designed for you to +forget about the jpeg+ and get on with the interesting bit: the pics of your younger and his pet.
3) All of my friends and family use PCs, and there is a chance that due to financial concerns, when I eventually replace my macbook pro (far in the future) I could switch to a pc. Does iphoto make transferring pictures more difficult? (If I understand correctly, it does not change the photo file, a jpeg is still a jpeg but I want to be sure)
A Jpeg is a Jpeg is a Jpeg. If you migrate to another app or an entire OS you can export the photos plus any and all metadata you've added to the Finder and move it on. (Caveat: You cannot export Faces. There is no agreed standard on any system for exchanging this info.)
4) I do not want iphoto to duplicate all of the pictures already in my library....if I import from finder-users-pictures, will it simply use those, or duplicate all 150gb worth of pictures?
It can do either. And this brings me back to the Referenced v Managed discussion above. By default, iPhoto will Manage the files, that is, it will copy them into the Library. You can choose not to, but I strongly recommend that you don't:
*How to do it:*
Simply go to iPhoto Menu -> Preferences -> Advanced and uncheck 'Copy Files to the iPhoto Library on Import'.
*What Happens:*
Now iPhoto will not copy the files, but rather simply reference them on your HD. To do this it will create an alias in the Originals Folder that points to your file. It will still create a thumbnail and, if you modify the pics, a Modified version within the iPhoto Library Folder.
*Some things to consider:*
1. Importing and deleting pics are more complex procedures. You have to to put the files where they will be stored before importing them. When you delete them you'll need to remove the files from the HD yourself.
2. You cannot move or rename the files on your system or iPhoto will lose track of them on systems prior to 10.5 and iPhoto 08. Even with the later versions issues can still arise if you move the referenced files to new volumes or between volumes.
3. Most importantly, migrating to a new disk or computer can be much more complex.
4. Because iPhoto has no tools for managing Referenced Files, if, for some reason, the path to the photos changes then you could find yourself resolving aliases for +each photo in the Library+ one by one.
My own opinion:
I've yet to see a good reason to run iPhoto in referenced mode unless you're using two photo organisers
If disk space is an issue, you can run an entire iPhoto Library from an external disk:
1. Quit iPhoto
2. Copy the iPhoto Library as an entity from your Pictures Folder to the External Disk.
3. Hold down the option (or alt) key while launching iPhoto. From the resulting menu select 'Choose Library' and navigate to the new location. From that point on this will be the default location of your library.
4. Test the library and when you're sure all is well, trash the one on your internal HD to free up space.
If you're concerned about accessing the files, There are many, many ways to access your files in iPhoto:
*For Users of 10.5 and later*
You can use any Open / Attach / Browse dialogue. On the left there's a Media heading, your pics can be accessed there. Command-Click for selecting multiple pics.
Uploaded with plasq's Skitch!
You can access the Library from the New Message Window in Mail:
Uploaded with plasq's Skitch!
*For users of 10.4 and later* ...
Many internet sites such as Flickr and SmugMug have plug-ins for accessing the iPhoto Library. If the site you want to use doesn’t then some, one or any of these will also work:
To upload to a site that does not have an iPhoto Export Plug-in the recommended way is to Select the Pic in the iPhoto Window and go File -> Export and export the pic to the desktop, then upload from there. After the upload you can trash the pic on the desktop. It's only a copy and your original is safe in iPhoto.
This is also true for emailing with Web-based services. However, if you're using Gmail you can use iPhoto2GMail
If you use Apple's Mail, Entourage, AOL or Eudora you can email from within iPhoto.
If you use a Cocoa-based Browser such as Safari, you can drag the pics from the iPhoto Window to the Attach window in the browser.
*If you want to access the files with iPhoto not running*:
For users of 10.6 and later:
You can download a free Services component from MacOSXAutomation which will give you access to the iPhoto Library from your Services Menu. Using the Services Preference Pane you can even create a keyboard shortcut for it.
For Users of 10.4 and later:
Create a Media Browser using Automator (takes about 10 seconds) or use this free utility Karelia iMedia Browser
Other options include:
1. *Drag and Drop*: Drag a photo from the iPhoto Window to the desktop, there iPhoto will make a full-sized copy of the pic.
2. *File -> Export*: Select the files in the iPhoto Window and go File -> Export. The dialogue will give you various options, including altering the format, naming the files and changing the size. Again, producing a copy.
3. *Show File*: Right- (or Control-) Click on a pic and in the resulting dialogue choose 'Show File'. A Finder window will pop open with the file already selected.
*If you want to edit the photo in another application:*
You can set Photoshop (or any image editor) as an external editor in iPhoto. (Preferences -> General -> Edit Photo: Choose from the Drop Down Menu.) This way, when you double click a pic to edit in iPhoto it will open automatically in Photoshop or your Image Editor, and when you save it it's sent back to iPhoto automatically. This is the only way that edits made in another application will be displayed in iPhoto.
5) Any other tips for someone completely new to macs and iphoto?
*To Push Home a point*
For someone inexperienced with Macs and inexperienced with iPhoto I cannot stress enough that Managed Library is the way to go. I understand there is comfort in seeing all those folders. But inside the Library that's all there is: all those folders, stored so that an inexperienced user can't grub things up!
The iPhoto Library Folder is a Package File. This is simply a folder that looks like a file in the Finder. The change was made to the format of the iPhoto library because many users were inadvertently corrupting their library by browsing through it with other software or making changes in it themselves. Want to see inside?
Go to your Pictures Folder and find the iPhoto Library there. Right (or Control-) Click on the icon and select 'Show Package Contents'. A finder window will open with the Library exposed.
Standard Warning: Don't change anything in the iPhoto Library Folder via the Finder or any other application. iPhoto depends on the structure as well as the contents of this folder. Moving things, renaming things or otherwise making changes will prevent iPhoto from working and could even cause you to damage or lose your photos.
Now close that window and forget about it.
So, once you've imported your photos to iPhoto in a Managed Library, the surplus duplicates are +your folders+. Of course, in time, trash them to get back the wasted disk space. But don't do it today or tomorrow. There's no hurry. When you feel confident that you understand how iPhoto is working and that's it's working for you, theat's the time to reclaim the space.
I organize my pictures by folders with the month and year.
If you want to duplicate your Folder Tree in iPhoto:
Start at the bottom of the hierarchy and drag a folder of images to the Album Heading in iPhoto. The pics will be imported and an Album of the same name created.
You can then create the Enclosing Folders in the iPhoto Window (File -> New Folder) and drag the Album to it. Folders can contain other Folders (Nested Folders) and Albums.
However, is your folder system date based? Then this form of organisation is a bit pointless in iPhoto when Smart Albums or the Calendar tool (Click on the wee magnifying glass in the Search Box) mean you can find the photos taken on any day, month or year at a click. With Smart Albums it's easy to find photos from specific range - say, June 3 to August 25, 2009 etc.
If your folder system is theme based - Xmas pics, Birthday pics etc, then you'll find Keywords are much more flexible, and can be used in conjunction with other criteria for making Smart Albums and searches.
6) This is very silly, but how do I uninstall picasa (I know how to uninstall on a windows but want to make sure I do things correctly on my mac!)
Drag the app to the trash and empty it.
Regards
TD
v

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)

Can I use Event structures in a subVI?

Hi,
I have a subVI (ProvaEv1.vi) that use an event structure inside. But when I use it in a VI (ProvaVI.vi) the event structure in the subVI doesn't catch the events.
I tried to insert the event structure in a while loop but it doesn't work too.
Could you help me?
Thanks Ius
Attachments:
ProvaVI.vi ‏11 KB
ProvaEv1.vi ‏15 KB

"iusn" <[email protected]> wrote in message news:[email protected]...
Thanks to all for your answers!
Wiebe! I tried to do as you suggested but I am not able to link the Event Reference Number inside te SubVI with the Event Register Number of the Register for Event in Main VI. There is e class conflict. Another question: how the SubVI can know the structure of the Register event outside?My aim was to create a modular structure but it seems very difficult, wath do you think about these problems?
The broken wire is related to your question. The event structure inside the sub vi knows about the events you register in the main, because the reference wire/control has a "strong" type. It contains information about the registered events. That is also why the wire is broken. You have to register all events, then create an indicator/control of the output. Use that control in the subvi. You have to do this every time the events change (you might use a type def if you use the control a lot).
Usually, the events that you would want to put inside subvi's are those related to user interface objects. I've had this a lot. You make a nice interface, but it's not reuseable, because the events are mixed with all the other events. Only solotion is to manually add the needed event cases in your program, and copy the code.
Even if you can put the events in a sub vi, I'd expect hanging vi's when more subvi's are registered for the same event. It's hard to tell without trying. So it's not a real solution either.
Like Chrisger suggested, the event callback might help a little, but they are tricky, and actually ment for this (they are intended for activex callbacks).
Perhaps you should look at XControls (if you use 8.2). It would be more work to replace your code to XControls, but once you're done, you have reusable code.. Haven't worked with them jet, but they are invented for this problem...
Regards,
Wiebe.
I have already create my application using event structure just in Main VI but it seems very complicate to read and keep update, I would have wanted to give modularity to my application.
Thanks Ius
SubVIEventMain.vi:
http://forums.ni.com/attachments/ni/170/203225/1/SubVIEventMain.vi
SubVIEvent.vi:
http://forums.ni.com/attachments/ni/170/203225/2/SubVIEvent.vi

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