Hi, Dan, I think the anecdote you mention happened with older Xilinx tools and an older/ancient mlib_devel version. I could be wrong about this, but I’m not convinced it applies to the current versions of things. Any evidence one way or the other would be most welcome.
Cheers, Dave > On Nov 11, 2015, at 10:37 AM, Dan Werthimer <[email protected]> wrote: > > > 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] > <mailto:[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] > <mailto:[email protected]>] > Sent: 03 November 2015 01:01 > To: Michael D'Cruze > Cc: [email protected] <mailto:[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] > <mailto:[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 > <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 > > > >
