Re: [Discuss-gnuradio] Saving the I/Q samples of multiple synchronized USRPs

[Marcus D. Leech]

On 07/20/2016 10:15 AM, avinash kalyanaraman wrote:

Thanks Marcus.

A quick follow-up question:

Should the length of my ethernet cables (to the GigE switch from each of the USRPs that I am trying to synchronize) match so that I get time-aligned I/Q samples ?

Thanks!

No, this is not something you need to worry about.  If your packets of samples entered the cables time-aligned, they will also leave the cables
   time-aligned, regardless of any length differences in the cables.

The same cannot be said on the analog side of things.

On Mon, Jul 18, 2016 at 12:20 PM, Marcus Müller <address@hidden> wrote:

They always align at the beginning. The file size difference is really just because due to the nature of general purpose hardware and GNU Radio's scheduling, there's no guarantee all blocks have written the same amount of data when you kill the flow graph.

Am 18. Juli 2016 17:46:13 MESZ, schrieb avinash kalyanaraman <address@hidden>:

Thanks Martin.

Is there any particular reason why I see different file sizes for the former (file-sink) case? I ctrl+c the hand edited python file to stop sample collection. The file sinks are unbuffered. Since they are of different sizes, is there a way to know which samples align in time ?

Thanks!

On Fri, Jul 15, 2016 at 5:30 PM, Martin Braun <address@hidden> wrote:

This'll work. However, the uhd_rx_cfile utility that comes with GNU
Radio will do that for you.

Cheers,
M

On 07/15/2016 11:33 AM, avinash kalyanaraman wrote:
> Hi all,
>
> I want to analyze the I/Q samples of 3 synchronized USRPs (connected to
> an Octoclock G). I have synchronized the USRPs according to
> http://files.ettus.com/manual/page_sync.html (i.e. I hand-modified the
> python file generated by GRC).
>
> I am feeding the output of my USRP Source block (with 3 channels and 3
> motherboards) to three file sink blocks. Would this be enough to save my
> synchronized I/Q samples ?
>
> I notice that the size of the three files (storing the I/Q samples)
> aren't the same after my run.
>
> Attached is also a screenshot of the GRC file.
>
> Thanks!
>
> --
> Avinash
>
>

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Sent from my Android device with K-9 Mail. Please excuse my brevity.

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Avinash

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