Thanks David and all, I unfortunately misspoke when it came to the power in the ADC clock signal. In fact, we had it at 9 dBm, not -9. Sorry for any confusion.
I set up the pulse generator to swing from +0.0 to +3.0 V at 1 us. To check on possible ringing, I also hooked up our pulse generator to an oscilloscope (I increased the pulse width to 10 ms, so I could see it). The waveform I observe has some severe overshoot both on the uptake and down. I've attached a drawing to explain what I mean. I can't seem to mitigate this overshoot with our little Agilent arbitrary waveform generator. Is this similar to the ringing seen at NRAO? If so, how is the 1 PPS generated by casperites? Thanks, Richard Black On Fri, Nov 7, 2014 at 11:29 AM, David MacMahon <dav...@astro.berkeley.edu> wrote: > Hi, Richard, > > On Nov 7, 2014, at 9:03 AM, Richard Black wrote: > > > Haven't heard anything for a while, so I thought I would add some more > detail about our system setup to see if it might shed some light on the > problem: > > > > 1 PPS Signal > > ----------------------------------------- > > Square pulse > > Frequency: 1 Hz > > Amplitude: 3 Vpp > > Offset: 0 V > > Width: 10 ms > > Edge Time: 5 ns > > That should be fine assuming the 3 Vpp is measured with the 50 ohm > termination in place. If you want to try a software sync, you can pass > "-S" (UPPERcase!) to the latest paper_feng_init.rb script. Check the > output of "paper_feng_init.rb --help" to see whether your version supports > that option. > > > ADC Clock > > ----------------------------------------- > > CW Tone > > Frequency: 200 MHz > > Power: -9 dBm > > It would be a good idea to increase the power level to +6 dBm as described > on this wiki page: > > > https://casper.berkeley.edu/wiki/ADC16x250-8_coax_rev_2#ADC16x250-8_coax_rev_2_Inputs > > But if the paper_feng_init.rb script reports that the ADC clocks are > locked and they measure approximately 200 MHz, then I think this is > unlikely to be the cause of the 10 GbE overflow problems (though it would > be great if the fix were this simple!). > > > For David, are there any red flags with our UBoot version or ROACH CPLD? > Here they are again for reference: > > > > From serial interface after ROACH reboot > > ================== > > U-Boot 2011.06-rc2-00000-g2694c9d-dirty (Dec 04 2013 - 20:58:06) > > ... > > CPLD: 2.1 > > ================== > > This matches one of our ROACH2s that is running and sending 10 GbE packets > in our lab: > > U-Boot 2011.06-rc2-00000-g2694c9d-dirty (Dec 04 2013 - 20:58:06) > > CPU: AMCC PowerPC 440EPx Rev. A at 533.333 MHz (PLB=133 OPB=66 EBC=66) > No Security/Kasumi support > Bootstrap Option C - Boot ROM Location EBC (16 bits) > 32 kB I-Cache 32 kB D-Cache > Board: ROACH2 > I2C: ready > DRAM: 512 MiB > Flash: 128 MiB > In: serial > Out: serial > Err: serial > CPLD: 2.1 > USB: Host(int phy) > SN: ROACH2.2 batch=D#6#69 software fixups match > MAC: 02:44:01:02:06:45 > DTT: 1 is 23 C > DTT: 2 is 26 C > Net: ppc_4xx_eth0 > > Hope this helps, > Dave > >
