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From: septer012 on 29 Jan 2010 18:07
Okay I managed a Radix-4 16 point DIF FFT. The problem im having is I am
not sure how to write C code to re-arrange the outputs.
From: kevin on 29 Jan 2010 23:07
On Jan 29, 6:07 pm, "septer012" <johnson.dani...(a)yahoo.com> wrote:
> Okay I managed a Radix-4 16 point DIF FFT.  The problem im having is I am
> not sure how to write C code to re-arrange the outputs.


Rather than a lengthy post showing the input locations and bit
reversed results, what you might do is download the first tutorial
(Sig. Processing and FFT) from www.fftguru.com (it’s right there near
the top of the page). Chapter 5 briefly covers some simple bit
reversals. Page 5-2 shows a 16 point radix 2 case, and page 5-5 shows
a 16 point radix 4 case.

And as noted, you could use one of the many bit reversal algorithms
(including the ones shown), or just use a look-up table (for small
FFTs, it’s real simple).

The tutorial is .pdf - if you can’t read .pdf, let me know. I’ll try
to post what you need here.

I’m still not sure if what you’re doing is actually radix 2 or radix
4, so you’ll have to examine your outputs and decide which one of the
above mentioned cases apply.

Kevin McGee
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