topic Re: LabVIEW FPGA Memory Compile Time Constants in LabVIEW

LabVIEW FPGA Memory Compile Time Constants

tcapuano-aps — Wed, 30 Jun 2021 21:25:48 GMT

Hi All,

I am trying to circumvent the limitation that LabVIEW FPGA doesn't support 2D Arrays, by leveraging memory. Right now, I have to set the depth of the memory manually, such that when I change the 2D Array dimensions, I need to change my #rows constant, #columns constant, and #elements constant (the memory size). I am looking for a method that allows me to set the memory size based on compile time constants.

Does anyone know anything?

Thanks,

Tom

Re: LabVIEW FPGA Memory Compile Time Constants

GerdW — Thu, 01 Jul 2021 06:32:07 GMT

Hi Tom,

@tcapuano-aps wrote:

Right now, I have to set the depth of the memory manually, such that when I change the 2D Array dimensions, I need to change my #rows constant, #columns constant, and #elements constant (the memory size). I am looking for a method that allows me to set the memory size based on compile time constants.

Can you explain the term "compile time constants"?

What is the difference of "compile time constants" to "constants in your code, evaluated when compiling the FPGA code"?

Re: LabVIEW FPGA Memory Compile Time Constants

tcapuano-aps — Thu, 01 Jul 2021 12:53:25 GMT

Hello,

Thanks for the reply.

I guess there really isn't a difference in this context.

I can't find a method to create a Memory using Block Diagram defined size, so I am hoping that there is some other nob I can spin at the project level. Perhaps, I can implement a Conditional Disable Structure with project defined symbols.

Another example of a similar problem is that the Array Size of a Fixed Size Array is not a constant according to the compiler.

Regards,

Tom

Re: LabVIEW FPGA Memory Compile Time Constants

GerdW — Thu, 01 Jul 2021 13:07:02 GMT

Hi Tom,

@tcapuano-aps wrote:

I can't find a method to create a Memory using Block Diagram defined size,

A memory block is created and defined in the project explorer. You can only use that memory block in your FPGA VI…

Which memory block sizes are we talking about?

@tcapuano-aps wrote:

Another example of a similar problem is that the Array Size of a Fixed Size Array is not a constant according to the compiler.

The result of the ArraySize function is a value (in a wire). Why should it be a "constant"?

Re: LabVIEW FPGA Memory Compile Time Constants

tcapuano-aps — Thu, 01 Jul 2021 13:59:43 GMT

Hi,

I agree that memory blocks are created and defined in the project explorer. This is the fundamental problem that I am trying to circumvent. The size of my memory block is a function of the #row and #columns of my matrix. Therefore, I would like to set the size of my memory block based on an equation that is resolvable at compile. This will make my API much more flexible.

I disagree with your argument that the size of a fixed array shouldn't be constant because it travels on a wire. All constants in LabVIEW still travel on wires. For comparison, this is how you can implement the behavior I would like in C. (https://stackoverflow.com/questions/3388656/how-to-determine-the-length-of-an-array-at-compile-time)

At this point, I guess these are more feature requests than anything else. I am just find it very difficult to implement good design practices in LabVIEW FPGA, given the limitations.

Another example is that there is no function that can initialize a Fixed Size Array.

Thanks,

Tom

Re: LabVIEW FPGA Memory Compile Time Constants

GerdW — Thu, 01 Jul 2021 14:07:28 GMT

Hi Tom,

@tcapuano-aps wrote:

The size of my memory block is a function of the #row and #columns of my matrix. Therefore, I would like to set the size of my memory block based on an equation that is resolvable at compile. This will make my API much more flexible.

Nice ideas: did you post them in the FPGA-IdeaExchange?

Again: which memory block sizes do we speak about?

Which API functions are we talking about?

Can you attach an example implementation of the desired API?

@tcapuano-aps wrote:

For comparison, this is how you can implement the behavior I would like in C.

I guess that C code will not create code for a FPGA target?

I still don't get the point of reading the size of a FixedSizeArray, create by you at edit time!? You already know its size, don't you?

@tcapuano-aps wrote:

Another example is that there is no function that can initialize a Fixed Size Array.

Simply place an array constant in your FPGA code and set its size: now you have your array initialized…

Re: LabVIEW FPGA Memory Compile Time Constants

JensG69 — Thu, 01 Jul 2021 16:06:22 GMT

I think Tom would like is to define the size of his FPGA memory by e.g. a "conditional diable symbol" before he runs his FPGA compilation...

Not sure if that is possible or not...

Regards, Jens

Re: LabVIEW FPGA Memory Compile Time Constants

Elias_Faraclas — Wed, 31 Aug 2022 12:33:40 GMT

This would indeed be a very nice feature.