Hi Dan, I was unaware that the compiler was able to remove unused logic, that's pretty useful. What I need is one real input to one complex output, so I'll check Nitish model and import it to ROACH2 if I need to, thanks for the info.
On a sidenote: It is possible still to join the slack? I remember something was mentioned about sending an email earlier this year. Thanks, Franco On Mon, Dec 30, 2019 at 3:10 PM Dan Werthimer <[email protected]> wrote: > > hi franco, > > are you looking for an FFT with a real input and complex output? > > you mentioned you are connected the unused inputs of the the > biplex_real-4x to ground. > this is useful, as the compiler should remove all the unused parts of the > FFT, > although it's probably not as resource efficient as a dedicated single > input real to complex FFT. > > if you need further reduction in resources, > nitish recently developed a single stream complex to complex fft. > nitish's posting on casper's snap slack channel is appended below . > > you could modify nitish's design to compute two reals in one complex FFT, > or a single real of N points in an N/2 complex FFT. > > best wishes, > > dan > > ------------------------------ > new messages > Nitish <https://app.slack.com/team/UMWDNQD7W> 10:54 PM > <https://casper-astro.slack.com/archives/CMNK6V19Q/p1576911266004700> > Hi, in reference to our previous discussion concerning the complex FFT of > a single stream of samples, we wanted to share the piece of the design > which worked, might prove useful to someone. So, we clock the SNAP at 250 > MHz and ADC is done at 250 MSps, thus one sample per clock cycle. We wished > to perform complex FFT, which would require a block taking 1 stream at 1 > sample per clock. The blocks available could only take powers of 2 samples > in parallel from a given stream, thus we had to find another way. Thanks to > Jack Hickish, we managed to make a small design with the FFT internal > blocks which performs the job. Please find attached. Channels 1 and 2 are > two separate streams (two distinct signals) coming from the mixer and they > contain 1 complex sample per clock cycle. The example shows a 2048 points > FFT. The unscrambler block is needed to put some order in the frequency > channels output. The channels from any one output have to be put in order > using this small code for example: > > for i in range(0, 1024): > spectrum1.append(channels1[i]) > spectrum1.append(channels1[2047 - i]) > > (edited) > Single_stream_complex_FFT.jpg > [image: Single_stream_complex_FFT.jpg] > > <https://files.slack.com/files-pri/THU1J9JDC-FRYDQAY5S/single_stream_complex_fft.jpg> > > > > > > On Mon, Dec 30, 2019 at 9:31 AM Franco <[email protected]> wrote: > >> Hello everyone, >> >> Is there an FFT block in the CASPER library (ROACH2) that can be used as >> 1 input -> 1 output? The closest thing I've found is the 'fft' block which >> has a minimum of 2 inputs. >> >> For now I'm using the fft_biplex_real-4x and zeroing 3 of the 4 inputs, >> but that's wasteful. I've also tried the Xilinx FFT block, but it has a >> strange problem where the noise floor increase considerably when injecting >> a tone at the middle point between two FFT bins. >> >> Thanks, >> >> Franco Curotto >> >> -- >> You received this message because you are subscribed to the Google Groups >> "[email protected]" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CACBfcEnPcxk-k4oFTD__%2BVYkTsGTSc%2B85uiLqejdEUthdGXwLA%40mail.gmail.com >> <https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CACBfcEnPcxk-k4oFTD__%2BVYkTsGTSc%2B85uiLqejdEUthdGXwLA%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> > -- > You received this message because you are subscribed to the Google Groups " > [email protected]" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAGHS_vFeEcLgYhcYLfL8KuYM4%3DzcDkmk4yC%2BgWWqc%2BttDi40pA%40mail.gmail.com > <https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAGHS_vFeEcLgYhcYLfL8KuYM4%3DzcDkmk4yC%2BgWWqc%2BttDi40pA%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "[email protected]" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CACBfcEn1O-RhKbRhpo2XDDgWhSpshQUadpMkq3KZ%3Dnstsgzwtw%40mail.gmail.com.
