Re: [Discuss-gnuradio] Python synchronisation of 2xUSRP N200 with SBX in one UHD container.

[Marcus D. Leech]

On 09/18/2017 03:49 PM, John Shields wrote:
> Thanks,
>             I have attached the GRC. I should note that before I run, 
> I wait until GPS is locked as evinced by the query_gpsdo_sensor utility:
>
>             GPS Locked
>             Trying to align the device time to GPS time...
>             GPS and UHD Device time are aligned.
>             last_pps: 1505763709 vs gps: 1505763709.
>             Printing available NMEA strings:
>             GPS_GPGGA: 
> $GPGGA,194149.00,4331.1729,S,17234.2461,E,2,09,1.5,32.2,M,8.5,M,,*7B
>             GPS_GPRMC: 
> $GPRMC,194149.00,A,4331.1729,S,17234.2461,E,0.2,0.0,180917,,*20
>             GPS Epoch time at last PPS: 1505763710.00000 seconds
>             UHD Device time last PPS:   1505763710.00000 seconds
>             UHD Device time right now:  1505763710.01897 seconds
>             PC Clock time:              1505763710 seconds
>
>             Done!
>
>             Kind Regards,
>
>                    John
>
> p.s. In Jan 2016, Nigel wrote that one of the steps needed to align 
> included 'Use integer_N_ mode for PLL' when I tried to use the method 
> you recommended, I got an error so ceased that line of investigation 
> for the moment - is integer_N_mode tuning required?
Integer-N will help, but my understanding of the ADF4351 is that the 
re-synch feature, enabled through timed commands, will also work.

Also, the "uhd_fft" command has a --phase-relations option that will 
plot relative-phase between two input channels.  You might look at that.