On 12/07/2020 11:24 AM, BERTOLINI Rodolphe via USRP-users wrote:
Dear all,
I put both mailing list (OAI and USRP) because both may have something to do
with my problem. I apologize if it is not appropriate.
I would like to synchronize a b210 and an x310 using a square signal generated
by a function generator. It has a 10MHz ref output, so I generate a 1Hz square
clock through a regular front output.
Except the output voltage, is there something I should care about ? I use them
with OAI, and they both are used as LTE base stations. When the base station is
on external ref, UE doesn't detect the base station. When the base station is
on internal ref, UE detects base station broadcasts and connects to the base
station.
Note 1 : PPS and REF are well detected by the USRP, when I change for example
PPS frequency, x310 led changes respectively.
Note 2 : only one USRP is used at the same time, I want to make it work first
with only one base stations, and then when base stations are both on and
synchronised
Note 3 : in OAI code, there is something like :
usrp_master_clock = 30.72e6;
args += boost::str(boost::format(",master_clock_rate=%f") % usrp_master_clock);
args += ",num_send_frames=256,num_recv_frames=256, send_frame_size=7680,
recv_frame_size=7680" ;
Is this master clock related to the sampling rate, or should it be changed to
10MHz?
The master clock rate is related to the available sampling rates, and
not the external reference frequency, which is 10MHz. The B210 is
quite flexible in its master clock rate, but the X310 is much more
limited in the master-clock rates it supports.
Note 4 : I looked at the spectrum of signal sent by base station, I don't see
any difference between the setup with external clock and the setup with
internal clock
Unless you have your spectrum analyser set-up for very-fine resolution,
you likely won't see much difference--the internal clocks are
already pretty good.
Any pointer would be much appreciated
Thank you.
Regards,
Rodolphe
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