On 06/18/2018 12:07 PM, Daniel Jepson wrote:
Dmitry,
The PPS and 10MHz should (at the very least) be generated using the
same base clock so they don't drift with respect to one another. Since
you are using multiple X310 devices, it is also important that the PPS
arrives at each device on the exact same cycle of the 10MHz
clock--otherwise you may see your timekeepers in each X310 offset with
respect to one another. There are no setup or hold specs for the X310
for PPS relative to 10MHz, but if you use equal length cables for both
signals you should achieve a decent level of consistency.
-Daniel
Daniel:
Not sure this is true?
The 1PPS signal is used as a "one shot", and as such, I don't think it
is required that it be synchronous to the 10MHz signal.
As long as both devices are "seeing" the 10Mhz and 1PPS with controlled
phase and delay for the individual signals (cable lengths, etc), it
shouldn't
matter, unless the FPGA requires that the PPS edge be synchronous
with the 10MHz edge, and I don't think it does.
On Mon, Jun 18, 2018 at 10:17 AM, Marcus D. Leech via USRP-users
<usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>> wrote:
On 06/18/2018 10:57 AM, Дмитрий Михайличенко via USRP-users wrote:
Is it important to have PPS signal aligned with reference 10 MHz
signal. In my case they come from different sources.
thanks,
Dmitry?
That shouldn't matter
пн, 18 июн. 2018 г. в 17:37, Marcus D. Leech via USRP-users
<usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>>:
On 06/18/2018 10:28 AM, Дмитрий Михайличенко via USRP-users
wrote:
The frequency is around 600 MHz. I also tried higher
frequencies. The offset is visible on picture attached.
thanks,
Dmitry
If you look here:
https://kb.ettus.com/UBX
You can see that for frequencies below 1GHz, you have to use
a 20MHz daughterboard clock for UBX to achieve synchronization.
I don't know if SBX will work correctly with a 20MHz
daughterboard clock, so you can't have "mixed" UBX + SBX on
the same
X310.
Also, integer-N tuning can help maintain better phase
synchronization characteristics:
https://files.ettus.com/manual/structuhd_1_1tune__request__t.html
<https://files.ettus.com/manual/structuhd_1_1tune__request__t.html>
пн, 18 июн. 2018 г. в 14:50, Дмитрий Михайличенко
<mdm...@gmail.com <mailto:mdm...@gmail.com>>:
Hi,
I have a couple of X310 each of them has UBX+SBX cards.
The devices are synchronized by external 10MHz + PPS
signal. But in my test I see random phase delay between
all channels that varies between test runs. The test
creates multi usrp device, sets up time and tunes to the
same frequency using timed command, then it captures
some buffers. The same external signal is supplied to
all antenna ports. Is it expected to have random delay
between channels? Is there any way to have constant
phase delay from run to run?
thanks,
Dmitry
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--
Daniel Jepson
Digital Hardware Engineer
National Instruments
O: +1.512.683.6163
daniel.jep...@ni.com <mailto:daniel.jep...@ni.com>
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