Hi Jack Sorry it’s taken me so long to come back (I’m going to write back to everyone shortly). I’ve been chasing a few hunches I’ve had which might have exonerated the FFT, but to no avail. Indeed the FFT does simulate OK, but in the majority of cases in hardware every other channel is a zero. I say in the majority of cases, because in one or two cases the design works correctly. I have not been able to find a reason for this yet.
BW Michael From: Jack Hickish [mailto:jackhick...@gmail.com] Sent: 03 November 2015 01:01 To: Michael D'Cruze Cc: casper@lists.berkeley.edu Subject: Re: [casper] FFT woes 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<mailto: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
