Using global variables

Similar Questions

• Using global variables in a device custom

  Hello world

  I have problems with the passing of data through my device customized using global variables. I want to allow a user to select a RIO device address when you set up the system definition file. This is recorded in a global variable using the hand Page VI. I would later use this RIO device address in RT driver to deploy a bitfile. I can hard-code, but it is much more convenient to use a global.

  When I try to store the address of the global variable, it updates the value temporarily (I confirmed that the structure of the event recognizes the change of value). When I click the node of the tree to define system linked to the Main Page VI and then click on it again, the hand Page VI runs again. I wrote the code to repopulate the address of device of RIO with the last value stored in the global variable, but it is empty. I've included the VI global variables in my build, so I can't imagine why it can reset this value.

  Any help would be appreciated!

  Thank you

  Mitch

  Have you tried to use the custom device properties to store this value instead of GVs?

  Configuration VI, you can set this property, and if I'm not mistaken, you can read these properties on the RT driver.

• Cannot use Global Variable in the Structure of the event

  I'm using LabVIEW 2009.

  In my LabView project, I have a global Boolean variable called EStop. I can read and write the global variable. If I double click on the global variable, it takes me to EStop.vi which includes a text button. EStop.vi is part of my project.

  In one of my report, I have a Structure of the event. If I go to one of the event handlers in this case Structure and right click and select Add event, I get a list of possible events. But this list does not EStop or an EStop events.

  I would like to add an event to EStop case: changed value.

  Why I can not add to a case of events events that include events on Global Variables as value changed?

  How can I add EStop: event changed my structure of the event value.

  
  

• Why LabVIEW example projects using Global Variables?

  I'm puzzled.  I've been pretty good programmers LabVIEW talks (including some who work for the OR) and came away with the impression that Global Variables should, as a general rule, be avoided, with functional Global Variables (alias VI Globals) generally preferred for "local memory".

  I have studied some of the example distributed with LabVIEW, 2012 and 2013, in particular the proposed acquisition in real time and am struck by the use of Global Variables, where I'd be inclined to use instead a FGV.  For examples, to stop all the loops on the RT target, the overall "All the RT loop Stop" is defined; 'Constants' of configuration (such as timeouts, Streme network names, the names of the journal folder) are kept as Globals; Streme network endpoints are stored in Globals.

  [Note - there is a weird spelling of the second word of the network Streme, above - when I tried to post with the correct spelling, I got an error message saying this word is 'not allowed in this community".]  I apologize for the offense, but I must confess that I do not understand what the problem with the help of the spelling of this word...]

  Why use Globals in these cases, rather than write a bunch of VIGs to hold these data?  Note that almost all these Globals are 'Read' essentially (written once when a resource is acquired, for example) or "Read Only" (treated as if they were a constant).  Indeed, read-only variables can be written as a Subvi with only an output terminal, acting as a (visible, due to the icon) constant.

  I can see advantages to this approach.  On the one hand, VIGs can have error bounds who run the data flow (I just spotted a bug "data flow" in code, I am developing that is based on this model, to read configuration data to an XML file in a world and in the same VI, Global wiring to a "use - me" terminal, but with no guarantee that I'll read the overall after I write it).

  It is, I suppose, a matter of 'speed' - perhaps Global Variables are 'faster' than VIGs (especially if the VIG 'sits' on an error line).  My thought, however, is that this difference is likely to be trivial, especially as these VIGs (or Globals) tend to become "occasional" calls (with the exception of the indicator 'all the loop Stop' which is called once per line).

  Are there other arguments or considerations that make a Variable global to a better choice than a VIG?  Is there a reason that LabVIEW developers put in these start-up of projects LabVIEW?

  BS

  I have to ask, how do you use functional Global Variables?  Like just a Get and Set?  If so, you can use a global variable.

  Yes, globals are faster and use much less overhead.  At the summits of CLA in recent years, we talked about using globals.  The most common use is for Write-Once-Read Many and writing-never-Read Many with configuration data.  It's a good idea to use globals with the constants that can change on you.  It turns out that the world will have the same performance as a constant in this case.  This is done so that you don't have 1 place to edit the 'constant '.

  The rule on "Globals are evil" actually goes back several years when NEITHER had the huge "people of the country are bad" vendata.  But NEITHER explains well how to do things properly.  So I found people, instead of using local variables, using the value property node.  It's even worse because the property causes thread swaps and kills your performance.  It wasn't until I shouted to people to use wires and shift registers I have seen improvements in the way in which people wrote their code.  So people are always riffling in the use of globals and decided to use FGVs with the EEG and fixed rather cases.  But this does not solve the problem of the conditions of race with critical data and you cause an additional burden.

  So from my experience, I use globals all the time for configuration data.  Yes, you must be careful about the race conditions.  But as long as you understand that it is a common and useful practice.

  I would not use a global variable for data that are constantly changing (use registers to offset or Action motor) and/or processes that have critical sections of code (use a motor of Action).

  NOTE: I use the definition of Mercer to FGV (a Get/Set only) and motor Action (many cases which specifically affect the data).

• Using global variables in all scripts

  Hello

  I have a SOAP client which runs the runScript method.

  SOAP requests to three, one after the other, call runScript and run a jsx on the server.

  Can I have some session-level variables / global whereby I can access via scripts?

  For example, during the execution of the first script, I put a variable. And even once during the second and third queries SOAP, I use the variable (defined in the 1st script) in the 2nd and 3rd scripts.

  How can I get the above?

  I would really appreciate some help on this.

  You can use the #targetengine or insertLabel methods.

  Incapacitated, I would say, of #targetengine, "session01" is the specific session will be exist until InDesign is running, which is not desirable. Those who will destroy only when you exit your application. I don't think that there is no collection for rescue here.

  However, insertLabel and extractLabel can be used on specific DOM objects, according to your need, including the app object.

  If you want to share variables between scripts on a document so that you can store variables on the document object:

  doc.insertLabel ("name", "value");

  So, once the document is closed all the labels are gone. You can choose according to your requirement, you want application-level globals (then use app.insertLabel), level of the document (then doc.insertLabel), spread of level, etc.

• Popup JavaScript does not work using global variables?

  I have a menu region "References" which contains links to several pages pop up indicating the access codes of valid data filtered for the location of the user. I tried to make this work in another page by changing the references page to global variables variables / application, but it does not work. Can anyone suggest a work around? Here is the code I use:
  
  Target URL in link

  javascript:callEmpPopup('P1050_ORG_ID')

  JavaScript

    function callMyPopup (formItem1,formRow1) {
      var formVal1 = document.getElementById(formItem1).value;
      var formVal2 = 1;
      var url;
    url = 'f?p=&APP_ID.:1056:&APP_SESSION.::::P1056_FACTORY_ID,P1056_ROW:' + formVal1 + ',' + formVal2;
    w = open(url,"winLov","Scrollbars=1,resizable=1,width=1000,height=600");
    if (w.opener == null)
    w.opener = self;
    w.focus();
    }

  Blair:

  Use a "Hidden" type page element defined on page 0 instead of a part of the application.

  CITY

• How to use global variables from a dll in another (not multi-threaded)

  With LabWindows/CVI. I try to be compatible with legacy code, so this isn't the best way to do things, but it saves me some headaches.

  I have a project/.dll called "GlobalBlock" that contains some parameters used widely throughout the program. The entire program consists of several DLLs, for the purpose of encapsulation.

  GlobalBlock.c contains:

  menu_sdef G_setprefs = struct
  {
  ... stuff

  };

  sys_fileheader_sdef Level1Version = struct
  {
  ... more

  };

  struct G_sys_flags sys_flags_sdef;

  In the dll that owns the variable, use the _export on this qualifier. This will ensure that it is placed in the list of the interface dll. In the application (dll or other) that wants to make reference to that variable, use the qualifier _import on it. This tells the system to use the associated import library that comes with the dll in order to resolve references running.

  JR

• use global variables

  Hello

  I have 3 steps in my application. I opened the first step, enter some data and move on to the second stage. then I type in some other data and switch to the third stage. Now, I want to display the data of the first stage in the third phase.

  Of course I could pass the data through the second and third stage...

  Is there something like a varaible overall for the whole application, that I can use on each stage?

  Thanks hibbert

  There are several ways to do so. I personally find using a singleton class that contains the required state very useful more as a hub to send events around to have. You can do a quick search on the forum of samples.

• How can I create and use global variables in busy border?

  to preserve the previous value while being used between parent and child symbol?

  For some reason, you actually have to call the function inside of another symbol (and not the bodies as before). New version of the same exercise with the following structure where each rectangle and the associated text is encapsulated in an object symbol :

  

  To make the accessible service for another symbol, you add SYM (the parameter of substr() is also adapted to the new id)

  Stage.compositionReady event handler:

  Total = 0;

  //-----------------------------------------

  SymincrementByInstanceNum = function (eClick)

  {

  Console.log (eClick.target.getAttribute ("id"));

  => "Stage_object2_yellowRect2_RoundRect" for example

  var num = eClick.target.getAttribute("id").substr (12, 1);

  Total += parseInt (num);

  SYM. $("total") .html ('total' + total);

  }

  Each of the object.yellowRect.Click event handler becomes:

  sym.getComposition () .getStage ().incrementByInstanceNum (e);

  

  The link given above has been updated and now includes the second version.

  Gil

• Digital control system, using limits of entry of data with global variables

  Hello!

  I have a Subvi with several digital control sliders. These control framerate, the pixel clock and exposure of a camera and their change in max/min/increment whenever one of them is changed - they are interdependent and get their information from the camera continuously during execution.

  I'm trying to remote control this VI, but during the passage of a value using global variables, it doesn't "stick".

  Example:

  The value for exposure is 237,48 Ms. different values are constrained to the nearest value. So if I pick 240,00 ms at the Subvi, he should know that this is not a valid value and change to Mrs. 237,48.

  But it is not do and I don't know why. When I enter the values manually, it works fine.

  Any suggestions?

  The limits on the controls that apply when their control from the front and is not passing values via the connector pane.

  You should use something like "line and force" within the VI to validate the values are within the range (maybe constrain data or return an error).

• Can I use the timestamp to a global variable that is published to network to reduce network traffic?

  I would use a couple of network-has published the global variables that will contain large groups of data.  I want to host them on a device, but read them in several - consider a distributed control system.  The data will be updated very rarely, but when that happens, I want that all my GUI to know quickly.  I have all the GUI, simply read data 4 x per second (which would be fast enough), but I was wondering if there is a more elegant solution (always using global variables).  If I read only the timestamp 4 x per second each of the HMI, compare to the last reading and then interrogate the integer variable if timestamps are different, which will require fewer resources that just enter the integer variable each time?  In other words, the read timestamp uses the same amount of resources as the reading of the entire variable?

  With really simple code, assuming that the cluster "Data" is big enough, made...

  .. .get me no benefit on...

  mark3545 wrote:

  Which means that they are already doing what I want anyway, no?  If the reader is updated when it changes the writer, I can survey as often I want without increased traffic, correct?

  That is right.

• Problem of global variables

  I have subVI´s of multiples that send data to the VI main when are called using global variables. Then the main VI must send these data to an another subVI´s called by an another VI main to show in its facades. It works perfectly when all SIX are executed in the LabVIEW environment, but when it's in main VI´s generation aplication, it's as if the global variables do not work because the data are always zero... I can´t find the cause of the error, I checked the construction features and there is nothing about the global variables, only the VI that located them in the summary project dependencies.

  What could be the error?

  You can use shared variables, you cannot use global variables. Shared variables can be local (on a PC) or network.

• Is it possible to replace occurrences of a global variable massively while also setting up the components of connector?

  I work through some of my old code now, looking to increase the performance where I can. Here's my situation:

  1. I used Global Variables to spread a few constants in my screws, instead of a proper typedefed cluster.

  2. execution does not have an extension, but no matter when I save the project, I would say 50 to 60 percent of the economy/compling time is spent on the screw of 300 or more with global variables. I suspect it has to do with the link between the overhead associated with the global.

  3. Ideally, I would like to replace this:

  

  With something like this:

  

  While also putting the connector of this pane:

  

  To do this:

  

  What is the VI server is capable of? You can assume that the VI in question have very predictable names, matching the regular expression:

  subname[0-9]^3
  

  Is it still worth it to replace?

  I don't know what you mean by compile time.  One of my big projects LabVIEW RT, which has about a thousand of screws, a lot of VIGs (FGVs), engines of the Action, even a few Globals and variable shared.  In my case, the thing that seems to "slow down" the compilation the most is the links to the report generation tool (I use Excel workbooks for 'drive' of experience and also save the data a bit).  If I do a building together, to build this routine and about 6 'support' routines (data analysis, utility Configuration, etc.), it may take a minute, but I can't find this excessive nor a charge (compared to the facility to isolate/encapsulate features in screws as FGVs).  So I guess I don't understand the "real problem"...

  Bob Schor

• global variable in the instrument Drivers

  Hello

  We design an instrument Driver for our devices. We have VI that does the same thing, but with different inputs and this entry is a collection of references.

  I would like to know if this VI can be contributed by these groups as global variables. Through this way, I hope that we will significantly optimizie our code.

  We are also looking for drivers to achieve certification by the OR so looking for any sort of solution if global will not be a good solution to achieve the optimization.

  Thanks in advance,

  VIvek

  I don't understand what you mean by "chipped". Using global variables magically will not make your code more efficient. It is used for the global variable, and there are places where they should not be used. Reasonable use must contain the data used by several processes, even if a queue is usually a better way to go.

  The best way to see how to write an instrument driver is to download recent instrument of the NI Instrument Driver Networkdrivers. Look for ones that are based on projects like these are made in 8.x and are fairly recent. You don't have to bother with the old drivers - they are a mess. You should be able to find something that looks like your instrument and use it as a model. There is also a Driver of Instrument wizard that comes with LabVIEW. Another source of information is the basis of knowledge of NOR. Do a search and you will find a lot of information. Like this: developing LabVIEW Plug - and - Play instrument Drivers.

  You should also read on the nugget of Ben on the engines of the Action.

• How to reword scope of global variables on a per instance basis?

  I have a legacy application of this unforutnatly makes a lot of use of global variables (not the functional kind).  If we want to run two instances of the first level VI simultaneously without using global variables collided with another, which is the least painful to achieve this way * without * having to build in an exe?

  I don't know if it'll work or not, but that would happen if you ran the screws in two different projects?   I might have to try that when I managed to find some free time.