Michael
It may be that your FFT is working fine. Are you using a window before the
FFT? The window can put zeros at odd bins if the input signal is just right.
You may try taking away the pfb block, and inputting random noise into the FFT
without any windowing.
if the input has samples that are repeating: 0,0,1,1,2,2,3,3 etc. that can put
zeros in the output too. Are you sure your inputs are correct? Are you using 4
inputs or 2 inputs? You should post a picture of you rmenu windows when you
are setting up the FFT so we can see how you are setting it up. If the numbers
for input streams are wrong you may get this problem.
If it is a roach2 FFT then there is a wierd problem with the library. You have
to set the scaling by ungraying and puttin in some number like 255 or 511 etc.
Then you can regray. The problem is that the set up window has no value at the
start and it can mess up things.
Also, open up the FFT block by clicking on the arrow to "look under the hood."
The FFT is created be matlab scripts and you can see all the innards of the FFT
alg. Look at all the layers and make sure things are all connected. Perhaps you
have some version of the casper lib that is bad.
Tim Madden
Argonne Lab
Chicago, USA
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Today's Topics:
1. FFT woes (Michael D'Cruze)
2. Re: FFT woes (Jack Hickish)
----------------------------------------------------------------------
Message: 1
Date: Tue, 3 Nov 2015 00:57:12 +0000
From: "Michael D'Cruze" <michael.dcr...@postgrad.manchester.ac.uk>
Subject: [casper] FFT woes
To: "casper@lists.berkeley.edu" <casper@lists.berkeley.edu>
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<am2pr01mb03856313813fcc07a4e818898a...@am2pr01mb0385.eurprd01.prod.exchangelabs.com>
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Dear all,
Following on from the email thread from Jonathan Kocz and Andrew Martens about
odd FFT outputs....
I've been experiencing similar inexplicable problems for a while now. Every
other channel in my output is invariably a zero. I've tried everything I can
think of, including solutions along the lines of those observed to work by
Jonathan and Andrew (black-boxing, changing mask parameters etc.), in addition
to wiping clean my libraries and re-syncing with casper-astro-soak-test. I've
even re-drawn the entire model from scratch. The results are always the same.
Below is a link to an example output.
https://dl.dropboxusercontent.com/u/38103354/32k_test_image.png
Hopefully it's clear from a_0 (note that a_0 is zoomed in, a_1 is not) that
every other channel outputs zero, and the interleaved a_0 and a_1 spectra (to
form the full 32k channel spectrum) are interleaving correctly to produce pairs
of zeroes. I've been trying various things for quite a while now, without
success and would appreciate some suggestions...!
Thanks
Michael
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Message: 2
Date: Tue, 3 Nov 2015 01:01:11 +0000
From: Jack Hickish <jackhick...@gmail.com>
Subject: Re: [casper] FFT woes
To: "Michael D'Cruze" <michael.dcr...@postgrad.manchester.ac.uk>
Cc: "casper@lists.berkeley.edu" <casper@lists.berkeley.edu>
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<CAG1GKS=t3fe4d5tvbi43n2tacju5geaaxabnwxeswu7vh3-...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Hi Michael,
Just so everyone is on the same page -- does your issue only show up in
hardware like Andrew/Jonathon's - i.e., in simulation the FFT works ok?
Jack
On 3 November 2015 at 00:57, Michael D'Cruze <
michael.dcr...@postgrad.manchester.ac.uk> wrote:
> Dear all,
>
>
>
> Following on from the email thread from Jonathan Kocz and Andrew Martens
> about odd FFT outputs?.
>
>
>
> I?ve been experiencing similar inexplicable problems for a while now.
> Every other channel in my output is invariably a zero. I?ve tried
> everything I can think of, including solutions along the lines of those
> observed to work by Jonathan and Andrew (black-boxing, changing mask
> parameters etc.), in addition to wiping clean my libraries and re-syncing
> with casper-astro-soak-test. I?ve even re-drawn the entire model from
> scratch. The results are always the same. Below is a link to an example
> output.
>
>
>
> https://dl.dropboxusercontent.com/u/38103354/32k_test_image.png
>
>
>
> Hopefully it?s clear from a_0 (note that a_0 is zoomed in, a_1 is not)
> that every other channel outputs zero, and the interleaved a_0 and a_1
> spectra (to form the full 32k channel spectrum) are interleaving correctly
> to produce pairs of zeroes. I?ve been trying various things for quite a
> while now, without success and would appreciate some suggestions?!
>
>
>
> Thanks
>
> Michael
>
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