Hi James, Thank you for your answer. Yes, I use and ADC for data acquisition. I understand the general idea of your system. What I don't understand is where you get the start time of the ROACH2. Is generated by the TRF? Is there a different system that initialize all the synchronized devices and that record the start time? Sorry if it is basic question.
Thanks, Franco On Thu, Mar 7, 2019 at 3:52 AM James Smith <jsm...@ska.ac.za> wrote: > Hello Franco, > > As I understand it, PTP wasn't terribly useful in our application (though > I wasn't involved with this directly). You can probably sync the little > Linux instance that runs on the ROACH2, but getting the time information > onto your FPGA may prove somewhat tricky. > > Are you using an ADC card in the ROACH2? Or is the data digitised > separately? > > What we've done with ROACH and ROACH2 designs in the past is more or less > this: > > - FPGA's clock comes from a timing & frequency reference (TFR). > - ROACH2 gets a 1PPS input from the same TFR. > - In the FPGA logic there's a counter which is reset as part of the > initialisation, and some logic that starts the counter going after a set > number of 1PPS pulses (two to three, I forget exactly now). > - The output of this counter is pipelined along with the data and then > sent out as part of the SPEAD data on the 10GbE network. > > The idea here being that you know with a fairly high degree of precision > which pulse your ROACH was initialised on. The counter that comes through > on the SPEAD packet counts in FPGA clock cycles (or multiples thereof, > perhaps you might want to count in spectra), and then you can use the start > time to calculate the timestamp of each packet (Unix time, MJD, whichever > your preferred reference is). > > Hope that helps. > > Regards, > James > > > On Wed, Mar 6, 2019 at 7:41 PM Franco <francocuro...@gmail.com> wrote: > >> Dear Casperiites, >> >> I was given the task of timestamping ROACH2 spectral data in a telescope >> that uses PTP (precision time protocol) as a synchronization protocol. I >> understand that ROACH's BORPH come preloaded with NTP (network time >> protocol) libraries/daemos, but PTP is preferred because is already in use >> in the telescope, and it achieves greater time precision. >> >> Does somebody know if it is feasible to compile/install PTP libraries in >> BORPH? >> >> Alternatively, we have though of sending the ROACH the current time >> through a GPIO pin using IRIG-B timecode standard. Has anybody done >> something similar in the past? >> >> Thanks, >> >> Franco >> >> -- >> You received this message because you are subscribed to the Google Groups >> "casper@lists.berkeley.edu" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to casper+unsubscr...@lists.berkeley.edu. >> To post to this group, send email to casper@lists.berkeley.edu. >> > -- > You received this message because you are subscribed to the Google Groups " > casper@lists.berkeley.edu" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to casper+unsubscr...@lists.berkeley.edu. > To post to this group, send email to casper@lists.berkeley.edu. > -- You received this message because you are subscribed to the Google Groups "casper@lists.berkeley.edu" group. To unsubscribe from this group and stop receiving emails from it, send an email to casper+unsubscr...@lists.berkeley.edu. To post to this group, send email to casper@lists.berkeley.edu.
