Subversion Repositories dblclockfft

# A Generic Piplined FFT Core Generator

This generic pipelined FFT project contains all of the software necessary to

create the IP to generate an arbitrary sized FFT.  The FFT has been modified

for operation in one of the following modes:

- Two samples in per clock and, after some delay, two samples out per clock.

  This uses 6 multiplies per FFT stage in the butterflies.  This was the purpose

  of the original `dblclkfft`.  (Why double clock?  I don't know.  Double-sample

  FFT might've been a better name.)

- One sample in per clock, with the `i_ce` line being high for every incoming

  sample--up to one sample per clock.  There's also options to run with at

  least one clock between samples, or even two clocks between samples (or more).

  This mode uses 3, 2, or 1 multiplies per FFT stage respectively.

- Eventually, I want to support a real FFT mode which will accept real samples

  input, and alternately produce real and imaginary samples output--or the

  converse for the inverse FFT.

The FFT generated by this project is very configurable.  By simple adjustment

of a command line parameter, the FFT created will either be a forward FFT or an

inverse FFT.  The number of bits processed, kept, and maintained by this

FFT are also configurable.  Even the number of bits used for the twiddle

factors, or whether or not to bit reverse the outputs, are all configurable

parts to this FFT core.

These features make this open source pipelined FFT module very different

and unique among the other open HDL cores you may find.

For those who wish to get started right away, please download the package,

change into the ``sw`` directory and run ``make``.  There is no need to

run a configure script, ``fftgen`` is completely portable C++.  Then, once

built, go ahead and run ``fftgen`` without any arguments.  This will cause

``fftgen`` to print a usage statement to the screen.  Review the usage

statement, and run ``fftgen`` a second time with the arguments you need.

# Current State

This particular version of the FFT core now passes all my tests.  It has

yet to meet hardware to be finally verified.

- The [FFT test bench](bench/cpp/fft_tb.cpp) doesn't yet have a threshold that

  adjusts with input parameters to determine success or failure (yet).

- I haven't started on the real-only version of this FFT.

While my previously stated goal ws to continue working with this core until it

has a real-FFT capability before releasing it back into the master branch,

I'm actually so excited that I got it to this point that I'm going to move

it from dev to master earlier, and come back to get the real only version.

# Commercial Applications

Should you find the GPLv3 license insufficient for your needs, other licenses

can be purchased from Gisselquist Technology, LLC.

Likewise, please contact us should you wish to fund the further development

of this core.

Watch this space if you are interested in a release under another license.

I'm thinking about relicensing this with a more permissive license.