[USRP-users] Time Synchronization between Two Channels on USRP X310

Jorge Chen superme991 at gmail.com
Fri Oct 2 11:54:03 EDT 2015


Hello Rob

I tried it few days ago, and it worked.
I didn't notice the time setting, or, actually, I didn't understand the
meaning of "time_spec_t" command.
Through your suggestion and I further search some related information, I
gradually realize it.

Thanks for your help!

Best Regards
Jorge






2015-09-26 1:32 GMT+08:00 Rob Kossler <rkossler at nd.edu>:

> Jorge,
> According to your code, you set the clock to zero and then sleep 1 sec and
> then attempt to stream at time=0.1 which is already 0.9 secs in the past.
> Maybe do something like the following:
> md.time_spec = uhd::time_spec_t(usrp->get_time_now()+0.1);
> Rob
>
> On Fri, Sep 25, 2015 at 12:23 PM, Jorge Chen via USRP-users <
> usrp-users at lists.ettus.com> wrote:
>
>> Hello usrp lists,
>>
>>
>>
>> We’re using USRP X310 with SBX, and we met the same issue as the
>> discussion [*Sync issue between the two TX channels of **X310*] in March
>> this year.
>>
>> It seems like the time of the 2 channels are not synchronized.
>>
>>
>> By the suggestion in the discussion before, we’ve updated the UHD version
>> from 3.7.2 to 3.8.2, and used the set_time_unknown_pps() command for time
>> sync, also defined the time_spec.
>>
>>
>> The setting is like below, and most of our applications are refer to the
>> examples.
>>
>>
>> However, the results are the same, the second channel still have a delay
>> about 6 us (as the picture below).
>>
>>
>> So, we wondered if there are still some settings we haven’t done yet.
>>
>> And what else we can do to solve this problem?
>>
>>
>> *Program*
>>
>> =====================================================================
>>
>> //setup the clock reference
>>
>> usrp->set_clock_source(‘external’);
>>
>> Sleep(1);
>>
>> //setup the ant, rate, bw,….
>>
>> .
>>
>> .
>>
>> .
>>
>> //setup the synchronization
>>
>> usrp->set_time_source(‘internal’);
>>
>> usrp->set_time_unknown_pps(uhd::time_spec_t(0.0));
>>
>> Sleep(1);
>>
>>
>>
>> //setup the metadata flags
>>
>> uhd::tx_metadata_t md;
>>
>> md.start_of_burst  =  true;
>>
>> md.end_of_burst  =  false;
>>
>> md.has_time_spec  =  true;
>>
>> md.time_spec = uhd::time_spec_t(0.1);
>>
>> while(not stop_signal_called ){
>>
>> tx_streamer->send(buffs, buff.size(), metadata);
>>
>> metadata.start_of_burst = false;
>>
>> metadata.has_time_spec = false;
>>
>> }
>>
>> =====================================================================
>>
>>
>> *Figure*
>>
>>
>> *[image: 內置圖片 1]*
>>
>>
>> Any suggestion is helpful.
>>
>> Thanks!
>>
>>
>> Jorge
>>
>> _______________________________________________
>> USRP-users mailing list
>> USRP-users at lists.ettus.com
>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>
>>
>
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