Sorry for this question but the problem is found: that was a cable from the 
1PPS source
which was broken...
To answer your question: it is a self made 1PPS/10MHz source with 10ns accuracy.

regards,

olivier

Le 24/03/2020 à 18:08, Marcus D. Leech via USRP-users a écrit :
> On 03/24/2020 12:49 PM, Olivier Ravard via USRP-users wrote:
>> Hi,
>>
>> In order to synchronize several devices, We used to use an external PPS and 
>> 10MHz
>> reference and call set_next_time_pps.
>>
>> This works fine since many years using UHD 3.9 and N210. We recently use 
>> X300 + TwinRx
>> using UHD 3.10.3 and it seems
>> that it does not work.
>>
>> It seems that set_time_next_pps has no effect because the metadata.time_spec 
>> of the
>> received streamed data always
>> corresponds to the delay from the usrp object creation.
>> Example:
>>
>>      - during the synchro procedure:
>>              usrp.set_time_next_pps(time_spec_t(1585067798, 0.0))
>>      - during receiving data:
>>              rx_stream->recv(&buff_sc16.front(), buff_sc16.size(), md, 1.0);
>>              cout << "received date :" << md.time_spec.get_full_secs() << " 
>> " <<
>> md.time_spec.get_frac_secs() << endl;
>>              // this line prints "received date :74 0.778126" if the usrp 
>> object was
>> created since around 74 secs
>>
>> Does this function change its behavior ?
>>
>> thanks
>>
>> olivier
>>
>>
> What type of 1PPS source are you using?
>
>
>
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