How to implement code behind RT FIFO Create

[sparkymark567]

How to implement code behind RT FIFO Create?

I would like to obtain the mean average of the last 200 data-points (sampled at 100Hz), and publish the running average at 10Hz.

My preferred solution is modeled on the RT FIFO that is available from within the LabVIEW Real Time module. I plan to have 4 VI's as follows:

1) "Averaging FIFO Create.vi"

Description: this VI will have similar functionality to: RT FIFO Create.

Inputs: String name, Int32 size, Boolean create if not found, Error Cluster error in

Outputs: Refnum fifo, Error Cluster error out

2)  "Averaging FIFO Write.vi"

Description: this VI will have similar functionality to: RT FIFO Write.

Inputs: Refnum fifo, Single element, Error Cluster error in

Outputs: Refnum fifo, Error Cluster error out

3)  "Averaging FIFO Read.vi"

Description: this VI calculates the mean average from the specified number of elements

Input: Refnum fifo, Int32 number of elements, Error Cluster error in

Outputs: Refnum fifo, Single average, Error Cluster error out

4)  "Averaging FIFO Delete.vi"

Description: this VI has similar functionality to RT FIFO Delete.

Inputs: Refnum fifo, Error Cluster error in

Outputs: Error Cluster error out

Unfortunately, I do not know how to implement the solution in LabVIEW.

Is the LabVIEW RT FIFO, implemented in LabVIEW or C?

I am not sure if it is possble to obtain the required functionality (e.g. dynamic memory allocation) in LabVIEW?

Then again, maybe it can be done in some other way?

How do I create the FIFO object/cluster and store it in memory? I also need a reference to the stored object/cluster.

Do I need to use LVOOP?, and if so can I hide the OOP from the user? e.g. by implementing the four VI's in a library?

Please advise.

Thanks
Mark

[Cory_K]

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Is the LabVIEW RT FIFO, implemented in LabVIEW or C?

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Thats a funny question. LabVIEW of course!

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I am not sure if it is possble to obtain the required functionality (e.g. dynamic memory allocation) in LabVIEW?

Then again, maybe it can be done in some other way?

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For FIFO functionality, you should take a look at 'lossy queues'. You can allocate a certain size for the queue, then use 'lossy enqueue'. This will exactly replicate the FIFO functionality you are looking for.

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How do I create the FIFO object/cluster and store it in memory? I also need a reference to the stored object/cluster.

Do I need to use LVOOP?, and if so can I hide the OOP from the user? e.g. by implementing the four VI's in a library?

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All you would need is a top level VI. Make the other 4 VI's you mentioned subVI's and call them in the top level VI. You can move this FIFO queue from subVI to subVI no problem.

[sparkymark567]

LabVIEW queues do not help.

For "Averaging FIFO Read.vi", I need to average all elements in the FIFO with-out dequeing any data.

I need a lossy FIFO/queue, just like RT-FIFO. But unfortunately, you can not read the data in an RT FIFO without removing it.

This is why I need to have my own implementation of a FIFO, rather than use the LabVIEW built in functions.

At a lower level, I (think) LabVIEW built in functions are actually written in C?

I am not sure whether it is possible to obtain the functionality of a LabVIEW RT-FIFO by using only LabVIEW itself?

To create a FIFO (with create if not found input) I will need some form of dynamic memory allocation and management.
Is there are a way to do this in LabVIEW RT?

 Thanks

Mark

[Cory_K]

Well I recommended queues, but if you need to operate on elements without dequeuing them,

you could use an array. Its slower, but it works.

The averaging would be pretty easy:

 

You would just need to find an efficient way to make the array FIFO.

Hmmm, let me think of an efficient solution to this, I will let you know if I come up with something.

[sparkymark567]

Thanks Cory, but that's obvious and does not solve my problem.

To create a FIFO (with create if not found input) I will need some form of dynamic memory allocation and management.
Is there any way to do this in LabVIEW RT?

The problem is, how to create the FIFO's (object/cluster) by name, and store/manage them in a dynamic list. I will need to Create  the refnum/reference to the FIFO,  so that it can be passed to the Read, Write and Delete VI's.

I could insert a new cluster into an array of FIFO (object/cluster), but then I do not have a refnum because I can not create one programmatically.