hi michael, what operating system are you using? we have seen problems where the FFT works in simulation, and doesn't produce correct results on the FPGA when we were compiling using a non-xilinx supported operating system. the problem occurred only for large FFT's - i think 8K or larger.
best wishes, dan On Wed, Nov 11, 2015 at 7:34 AM, Michael D'Cruze < [email protected]> wrote: > 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:[email protected]] > *Sent:* 03 November 2015 01:01 > *To:* Michael D'Cruze > *Cc:* [email protected] > *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 < > [email protected]> 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 > > >
