FPGA: N-point FFT with arbitrary length data

[elyte_dev]

Hi,

I am developing an FPGA application (PCIe-7857) that acquires variable length data (between 5k and 1M samples) where the length is only known at runtime. I want to perform a 8192-point FFT on this data. is this possible on the FPGA target or do I need to push the data to the host to do the FFT there?

[Terry_ALE]

See https://www.ni.com/docs/en-US/bundle/labview-fpga-module/page/lvfpga/fpga_fft.html

FFT size—Specifies the length of the transform that this Express VI calculates. When you select Single Channel, Single Sample in the Input Format section, valid options are powers of two between 8 and 8,192. When you select Single Channel, Multiple Samples in the Input Format section, valid options are powers of two between 8 and 65,536. The default is 64.

[UMASO]

Hello, while the length of data acquisition varies at run-time, is FFT length fixed to 8,192?  Or is FFT length required to be determined at run-time as well?

[Terry_ALE · Accepted solution]

This function has the FFT length fixed.  The Xilinx FFT IP may be more flexible, see https://www.xilinx.com/products/intellectual-property/fft.html

[elyte_dev]

FFT length is fixed.

[elyte_dev]

I know this doc page, but it didn't provide the info I needed (or I didnt understand it). I've used the host FFT vi before which performs N-point FFT with arbitrary length data and expected the FPGA vi to behave similarly.