Hi Tim, Thanks for coming back to me. Indeed I am windowing and will give your suggestion of removing the PFB block a try. The current hardware setup is a CW generator plus noise generator, which together are well above the noise floor of the ADC (in fact a power meter shows the integrated power is only a few dB below the ADC's absolute max).
Could you elaborate on your suggestion of ungreying the scaling on the FFT? Are you referring to the hardcode shift schedule? I've tried this in a few designs but it hasn't made the difference. The default option seems to be "[]" rather than a completely blank space in the libraries I'm using, however.... I'm fairly used to diving under the mask and looking around. I've had to make a few manual mods to the PFB (adding pipelines for example) to get 128k-point (65536 channel) designs to compile. The FFT looks fine under the mask. Cheers Michael -----Original Message----- From: Madden, Timothy J. [mailto:tmad...@aps.anl.gov] Sent: 03 November 2015 20:25 To: casper@lists.berkeley.edu Cc: Michael D'Cruze Subject: RE: casper Digest, Vol 96, Issue 1. FFT woes (Michael D'Cruze) 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 ________________________________________ From: casper-boun...@lists.berkeley.edu [casper-boun...@lists.berkeley.edu] on behalf of casper-requ...@lists.berkeley.edu [casper-requ...@lists.berkeley.edu] Sent: Tuesday, November 03, 2015 2:11 PM To: casper@lists.berkeley.edu Subject: casper Digest, Vol 96, Issue 1 Send casper mailing list submissions to casper@lists.berkeley.edu To subscribe or unsubscribe via the World Wide Web, visit https://calmail.berkeley.edu/manage/list/listinfo/casper@lists.berkeley.edu or, via email, send a message with subject or body 'help' to casper-requ...@lists.berkeley.edu You can reach the person managing the list at casper-ow...@lists.berkeley.edu When replying, please edit your Subject line so it is more specific than "Re: Contents of casper digest..." 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> Message-ID: <am2pr01mb03856313813fcc07a4e818898a...@am2pr01mb0385.eurprd01.prod.exchangelabs.com> Content-Type: text/plain; charset="us-ascii" 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 -------------- next part -------------- An HTML attachment scrubbed and removed. HTML attachments are only available in MIME digests. ------------------------------ 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> Message-ID: <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 > -------------- next part -------------- An HTML attachment scrubbed and removed. HTML attachments are only available in MIME digests. End of casper Digest, Vol 96, Issue 1 *************************************