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

Koyel Das (Vehere) koyel.das at vehere.com
Wed Mar 6 00:06:55 EST 2019


Okay so is it enough to use timed tuning to get constant phase difference each time?


Koyel Das
Senior – Product Engineer

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________________________________
From: Marcus D. Leech <patchvonbraun at gmail.com>
Sent: Wednesday, March 6, 2019 10:14:56 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 11:40 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: 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 9:49:57 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 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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