A Labview program with 4 DMA FIFO on FPGA card which can support only 3 DMA

[Alexis38]

Hello,

I'm a beginner on LabVIEW FPGA, in my work placement I work on the program of a previous trainee, he has over his work placement and he has published this program in his report.

The problem on his program, it's he has set 4 DMA FIFO on it, but the FPGA card (NI PXI-7951) where we work me and the trainee support only 3 DMA, so I can't run the program, I have this error :

I wonder if it's a bug or anything else, any ideas ?

[crossrulz]

It is not a bug.  Most FPGA cards only have 3 DMA channels.  If you used a fourth, then you get yelled at.

Now I would question if you actually even need these DMA channels.  From what I can gather from the VI, you could remove the two DMAs that are being read.  Those could be simple controls on the front panel that you could write to directly in your host program.  Your write DMA channels may still be needed if you need to read every value that is read from the FPGA.

[Hooovahh]

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Alexis38 wrote:

I wonder if it's a bug or anything else, any ideas ?

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This is a feature.  It makes sure the code you write will work on the hardware it is compling for.  In this case it will not.  Reuce the number of DMAs used, or use hardware that has the number of DMAs you need.

[Jacobson-ni]

A lot of our older devices do only have access to 3 DMA channels.  Newer targets tend to have more available but we do list how many are on each specific device in the following KB.

http://digital.ni.com/public.nsf/allkb/0A008919E1551B1A86257B9D00764FC4

In addition to what crossrulz stated about changing some of your FIFOs to read front panel controls, you could also build an array out of those two values and pass the elements through a single FIFO similar to what is done in this community example.

https://decibel.ni.com/content/docs/DOC-6303

[thoult]

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@Jacobson-ni wrote:

A lot of our older devices do only have access to 3 DMA channels.  Newer targets tend to have more available but we do list how many are on each specific device in the following KB.

http://digital.ni.com/public.nsf/allkb/0A008919E1551B1A86257B9D00764FC4

In addition to what crossrulz stated about changing some of your FIFOs to read front panel controls, you could also build an array out of those two values and pass the elements through a single FIFO similar to what is done in this community example.

https://decibel.ni.com/content/docs/DOC-6303

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Or bit packing them.

[Alexis38 · Accepted solution]

Sorry to reply as late, thank you for your answer thank to your help I could change my program, now the program run with 3 three DMA, I used a array for put 2 signals in only one FIFO DMA.

I show the program, which can help someone with the same problem.