Hi, Franco, Are you trying to use a 140 MHz sample clock? 140 Msps operation in 16 input mode is supported. It should be very similar to how we ran this ADC board for the PAPER correlator (200 Msps in 16 input mode). We did not have duplicate samples, so that sounds kind of strange to me.
FWIW, there are some frequency limitations based on the MMCM limitations in the Virtex 6 FPGA on the ROACH2. These are described here: https://casper.ssl.berkeley.edu/wiki/ADC16x250-8#ADC16_Sample_Rate_vs_Virtex-6_MMCM_Limitations <https://casper.ssl.berkeley.edu/wiki/ADC16x250-8#ADC16_Sample_Rate_vs_Virtex-6_MMCM_Limitations> The text reads somewhat cryptically, but if you read it in conjunction with the Virtex 6 MMCM documentation and the HMCAD1511 documentation, it will hopefully be clear. HTH, Dave > On Apr 2, 2019, at 15:53, Franco <francocuro...@gmail.com> wrote: > > Hi Casperites, > > I'm working in some project that uses a ROACH2 and an adc16x250-8 ADC board. > When I check the raw data from the ADC using a snapshot block I see this > weird effect where two consecutive samples have always the same value, as > shown in this image: > https://my.pcloud.com/publink/show?code=XZMRx67Zpj7XjnkE5PypVuuDCB9Mhu8IJJ37 > <https://my.pcloud.com/publink/show?code=XZMRx67Zpj7XjnkE5PypVuuDCB9Mhu8IJJ37> > > According to an ex-coworker, this is the expected behavior of the adc16x250-8 > board in 16 input mode, because of some constraints in the communication > between the ADC and the FPGA, the FPGA must run at twice the speed to > correctly receive the sampled data. However, couldn't find any explicit > mention of this phenomenon in the CASPER website or mailing list. Can someone > confirm this is the correct behavior so I can get peace of mind :)? > > Some info of my test: > - Board: ROACH2-rev2 > - ADC: ADC16x250-8 coax rev2 > - ADC mode: 16 inputs (demux 1, using David Macmahon initalization code) > - User IP Clock Rate: 140 MHz > - Actual clock frequency used in the adc board: 140MHz > > Thanks, > > Franco Curotto > > > -- > 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 > <mailto:casper+unsubscr...@lists.berkeley.edu>. > To post to this group, send email to casper@lists.berkeley.edu > <mailto: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.
