Using global variable

[govindsankar]

Hi,

I have always learned that using global variables in software engineering is not the right method. So I am going to do a task where I need to communicate between different VIs. So can you please help me by telling me what is the alternate method to communicate between VIs if using global variables is wrong. Thanking You.

Govind Sankar Nair

Student Master of Science

University of Applied Sciences Darmstadt

[GerdW · Accepted solution]

Notifier, queues, channels, events, ...

[govindsankar]

I need to share data between VIs. So using notifier, queues, channels etc, I can do that? Please kindly do reply. Thanking You.

[ainnrc · Accepted solution]

@govindsankar
Yes. Data can be passed from two different VI's using either notifier, queues, channels etc while still following LV dataflow. You can search for examples to see how those method works.

[govindsankar]

Thank You very much for your kind reply, I will do as you have explained.

[jwscs]

the main problem are race conditions for the read-write-access.

you have also the option of wrapping the global access with a semaphore

or use a data value reference (DVR).

in most cases a queue / channel is the way to go for communicating between loops as the others have suggested.

regards

[Yamaeda]

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@GerdW wrote:

Notifier, queues, channels, events, ...

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Assuming Govind isn't asking about how to get data from 1 VI to Another in the normal circumstance, in which case direct wiring through the connector pane is the answer. 🙂

/Y

[crossrulz]

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@govindsankar wrote:  I have always learned that using global variables in software engineering is not the right method.

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There is a time and place...Are Global Variables Truly Evil?

[govindsankar]

No, I am talking about different VIs in a project, one VI acquiring the data and another VI needs to work on it. So the first VI should have data in some kind of memory for the second VI to access. This is where my doubt is, I am currently going through queues to find out how this can be done. If anyone has any access to any material that will help me in doing the same, it would be very helpful. Thanking You. 

[Yamaeda]

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@govindsankar wrote:

No, I am talking about different VIs in a project, one VI acquiring the data and another VI needs to work on it. So the first VI should have data in some kind of memory for the second VI to access. This is where my doubt is, I am currently going through queues to find out how this can be done. If anyone has any access to any material that will help me in doing the same, it would be very helpful. Thanking You. 

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Yes, depending on how fast collecting and analysing data is, you can either use the easy Connector pane out from data gathering, to Connector pane in of the analysing VI, i.e. normal dataflow.

The 2nd most common option is to look at the "Queue based Producer/Consumer" example and send all data collected to a queue, and have an analysis queue.

/Y