[USRP-users] different phase difference using splitter on each run

Marcus D. Leech patchvonbraun at gmail.com
Tue Mar 5 23:44:56 EST 2019


On 03/05/2019 11:40 PM, Koyel Das (Vehere) wrote:
>
> Hi,
>
>
> By tuning commands I understand you mean command of synchronization 
> for frequency tuning? But then in which other places I have to use the 
> timed commands like in gain, sample rate etc also do I have to use 
> timed commands? If so what are those commands? I am not getting a 
> clear example of this.
>
>
> Regards,
>
The tuning commands are the critical ones--because, as I explained, 
that's when the synthesizers are programmed, and the
   "resynch" pulse has to happen at the same time, hence, timed tuning.


>
> Koyel Das
> Senior – Product Engineer
>
> Vehere | Proactive Communications Intelligence & Cyber Defence
> M: +919051132173 | T: +91 33 40545454 | F: +91 33 40545455 | W: 
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> ------------------------------------------------------------------------
> *From:* Marcus D. Leech <patchvonbraun at gmail.com>
> *Sent:* Wednesday, March 6, 2019 9:49:57 AM
> *To:* Koyel Das (Vehere); 'USRP-users at lists.ettus.com'
> *Subject:* Re: [USRP-users] different phase difference using splitter 
> on each run
> On 03/05/2019 11:17 PM, Koyel Das (Vehere) wrote:
>>
>> So basically I have to insert the following line
>>
>>
>> usrp->set_command_time(cmd_time);
>>
>>
>> before the code where I need timed operations and then at the end of 
>> the code I insert
>>
>>
>> usrp->clear_command_time();
>>
>>
>> ??
>>
> The tuning commands in particular.
>
>
>>
>> Koyel Das
>> Senior – Product Engineer
>>
>> Vehere | Proactive Communications Intelligence & Cyber Defence
>> M: +919051132173 | T: +91 33 40545454 | F: +91 33 40545455 | W: 
>> www.vehere.com <http://www.vehere.com/>/
>> /
>> /unnamed 
>> <https://www.linkedin.com/company/vehere-interactive-p-ltd>unnamed 
>> (1) <https://twitter.com/VehereIndia>unnamed (2) 
>> <https://www.facebook.com/VehereIndia/>
>>
>> Vehere is the proud recipient of the Fastest Growing Technology 
>> Company Awards in India & Asia since 2012!/
>>
>> The content of this e-mail is confidential and intended solely for 
>> the use of the addressee. The text of this email (including any 
>> attachments) may contain information, which is proprietary and/or 
>> confidential or privileged in nature belonging to Vehere Interactive 
>> Pvt Ltd and/or its associates/ group companies/ subsidiaries. If you 
>> are not the addressee, or the person responsible for delivering it to 
>> the addressee, any disclosure, copying, distribution or any action 
>> taken or omitted to be taken in reliance on it is prohibited and may 
>> be unlawful. If you have received this e-mail in error, please notify 
>> the sender and remove this communication entirely from your system. 
>> The recipient acknowledges that no guarantee or any warranty is given 
>> as to completeness and accuracy of the content of the email. The 
>> recipient further acknowledges that the views contained in the email 
>> message are those of the sender and may not necessarily reflect those 
>> of Vehere Interactive Pvt Ltd. Before opening and accessing the 
>> attachment please check and scan for virus. WARNING: Computer viruses 
>> can be transmitted via email. The recipient should check this email 
>> and any attachments for the presence of viruses. The company accepts 
>> no liability for any damage caused by any virus transmitted by this 
>> email.
>> ------------------------------------------------------------------------
>> *From:* Marcus D. Leech <patchvonbraun at gmail.com> 
>> <mailto:patchvonbraun at gmail.com>
>> *Sent:* Wednesday, March 6, 2019 9:22:22 AM
>> *To:* Koyel Das (Vehere); 'USRP-users at lists.ettus.com 
>> <mailto:USRP-users at lists.ettus.com>'
>> *Subject:* Re: [USRP-users] different phase difference using splitter 
>> on each run
>> On 03/05/2019 10:41 PM, Koyel Das (Vehere) wrote:
>>>
>>> The timed commands are as follows in rx_multisamples.cpp
>>>
>>>
>>> if(sync=="now"){
>>>
>>> 	//This is not a true time lock, the devices will be off by a few RTT.
>>>
>>> 	//Rather, this is just to allow for demonstration of the code below.
>>>
>>> 	usrp->set_time_now(uhd::time_spec_t(0.0));
>>>
>>> 	}
>>>
>>> 	else if (sync == "pps"){
>>>
>>> 	usrp->set_time_source("external");
>>>
>>> 	usrp->set_time_unknown_pps(uhd::time_spec_t(0.0));
>>>
>>> 	boost::this_thread::sleep(boost::posix_time::seconds(1)); //wait 
>>> for pps sync pulse
>>>
>>> 	}
>>>
>>> 	else if (sync == "mimo"){
>>>
>>> 	UHD_ASSERT_THROW(usrp->get_num_mboards() == 2);
>>>
>>> 	
>>>
>>> 	//make mboard 1 a slave over the MIMO Cable
>>>
>>> 	usrp->set_clock_source("mimo", 1);
>>>
>>> 	usrp->set_time_source("mimo", 1);
>>>
>>> 	
>>>
>>> 	//set time on the master (mboard 0)
>>>
>>> 	usrp->set_time_now(uhd::time_spec_t(0.0), 0);
>>>
>>> 	
>>>
>>> 	//sleep a bit while the slave locks its time to the master
>>>
>>> 	boost::this_thread::sleep(boost::posix_time::milliseconds(100));
>>>
>>> 	}
>>>
>>> 1. "now", 2 ."pps" and 3. "mimo"
>>>
>>> I was using "now" but still I don't get same phase difference in 
>>> each run. Is there any other time command that I have to use or what 
>>> do I have to set?
>>>
>>> Regards,
>> Ah!  You have a misunderstanding about what I mean by "timed commands".
>>
>> See the "test_timed_commands" example in the source code tree.
>>
>> See also the documentation here:
>>
>> https://files.ettus.com/manual/page_sync.html
>>
>> Basically, you need to make sure that all the devices agree on what 
>> time it is (if you have only one device, this is "easy").  Once you 
>> have that,
>>   THEN, you need to make sure that all the RF synthesizer tuning 
>> happens at precisely the same instant, so that the re-synch feature
>>   (if the device has one) can be triggered at exactly the same time.
>>
>> Without that, the synthesizers are free to "lock" at any phase-angle 
>> with respect to the reference clock, and further the reference
>>   divider in a synthesizer is guaranteed to be in the same state 
>> across all synthesizers, even when they're using the same
>>   reference clock.  This is what the "resynch" hardware signal is all 
>> about, and what the set_command_time()/clear_command_time()
>>   API is all about.
>>
>>
>>
>>
>

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