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fpga FFT Length 8 problems?

So I am developing using a PXI-7953R and I am trying to get some FFT calculations done inside the FPGA where the source data comes from the host computer.  Things work fine when I use the FFT Express VI and set it up for "Inside Single-Cycle Timed Loop", "Single Channel, Single Data", but only when I am doing so with a fft length of 16.  Once I configure it to be of length 8, the FFT just does not send anything out.

 

I have re-written (or re-drawn) my code several times and still nothing works.  The only thing that I have gotten to show values is when my input data is a fixed-size array on the FPGA, but not when I am using a FIFO to send the data into the loop that contains the FFT.

 

In the attached source code, see the vi named "Host-Top-Level-Fft-8-Inside.vi" and you will see how the program flows.  I was wondering if anybody knew any "pertinent" information that I may have skipped over in the documentation such as about using a feedback node somewhere...etc

 

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I have attached a VI Snippet of the crucial code (with all probes removed for simplicity purposes)

 

Also, is it bad that I am passing data directly from a Host-to-Fpga FIFO into the FFT Express VI?

 

 

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Passing data directly to the Host-to-FPGA FIFO shouldn't be a problem.

 

Hmm, that is rather odd. The error seems to be a timeout at FIFO Write, because the FFT Express VI never produces a true for "output valid" for some reason.

I'll poke into it further and let you know if I find anything.

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