Re: [Discuss-gnuradio] clock synchronization by message passing

[John Malsbury]

"how can i make the usrp send its time when configured for synchronization?"

I might be misunderstanding the question, but here's an answer.  The USRP source outputs stream tags on the first sample when streaming.  The three tags are 1) rx_time 2) rx_rate 3)  frequency.  Using (1) and (2), you should be able to determine and track the time of the USRP.

You would use set_command_time for anything with commands - gpio, tuning, etc.  This is in the control plane. You do timed bursts in the data plane with stream tags -> tx_sob, tx_time, tx_eob.

If these terms are foreign to you, Google "introduction to stream tags" by Tom R.

-John

On Sun, Jun 16, 2013 at 12:02 PM, Jay Prakash <address@hidden> wrote:

I think i can use set_command_time (which i guess set the next time of transmission/command?).

how can i make the usrp send its time when configured for synchronization?

Jay Prakash 

Senior Undergraduate 

Electronics Engineering

IIT (BHU)

VARANASI

+91-9559475258

http://about.me/jay.prakash/

http://www.linkedin.com/profile/view?id=91120191&trk=hb_tab_pro_top

On Sun, Jun 16, 2013 at 11:58 PM, John Malsbury <address@hidden> wrote:

"XML_RPC block in the new gr-extras"

XML_RPC would have been subject to the same limitations.  It could only call set_time_next_pps if set_time_next_pps was in the uhd_sink/source blocks.  Maybe you can update them to include the function.

Let me ask a more fundamental questions - why do you want to reset the time?

-John

On Sun, Jun 16, 2013 at 11:20 AM, Jay Prakash <address@hidden> wrote:

so do we have any other block to do that. I did'nt find XML_RPC block in the new gr-extras

Jay Prakash 

Senior Undergraduate 

Electronics Engineering

IIT (BHU)

VARANASI

+91-9559475258

http://about.me/jay.prakash/

http://www.linkedin.com/profile/view?id=91120191&trk=hb_tab_pro_top

On Sun, Jun 16, 2013 at 11:43 PM, Adeel Anwar <address@hidden> wrote:

> so i checked the new grextras wiki it has uhd_control block i guess that can be used for this job.

uhd_control block  supports only a subset of usrp-functions (exposed through gr-uhd) e.g. "set_command_time", set/get_gain/freq etc BUT currently it doesn't support "set_time_now()"
https://github.com/guruofquality/grextras/blob/master/lib/uhd_control_port.cpp

-Adeel

On Sun, Jun 16, 2013 at 11:06 AM, Jay Prakash <address@hidden> wrote:

thanks for the clarification

so i checked the new grextras wiki it has uhd_control block i guess that can be used for this job.

Jay Prakash 

Senior Undergraduate 

Electronics Engineering

IIT (BHU)

VARANASI

+91-9559475258

http://about.me/jay.prakash/

http://www.linkedin.com/profile/view?id=91120191&trk=hb_tab_pro_top

On Sun, Jun 16, 2013 at 11:05 PM, John Malsbury <address@hidden> wrote:

The GPSDO can provide an "internal" 10 MHz/1 PPS signal.  I'm not sure if that's what you meant or not:  https://www.ettus.com/product/details/GPSDO-KIT

AFIAK, you cannot set the time of a USRP with a message. You may be able to use the XML_RPC block in gr-extras to call the function if it is exposed through gr-uhd.

-John

On Sun, Jun 16, 2013 at 10:30 AM, Jay Prakash <address@hidden> wrote:

how can we set the time of usrp by sending it message. I know there are function to (usrp.set_time_now()) do this from from top block variable but can this be done by sending message at usrp port . 

We can give internal reference signal of 10MHz  but is there also a way to give pps signal internally i.e. without using any external hardware.

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