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Re: [Discuss-gnuradio] How to capture fixed length burst of samples (to

From: Dan CaJacob
Subject: Re: [Discuss-gnuradio] How to capture fixed length burst of samples (to avoid overflow)
Date: Thu, 01 Mar 2012 20:16:44 -0500
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On 03/01/2012 10:57 AM, Nick Foster wrote:
The UHD "rx_samples_to_file" example will do this for you.


On Thu, Mar 1, 2012 at 3:22 AM, Rickard Radio <address@hidden <mailto:address@hidden>> wrote:

    Hi list,

    Two questions:
    a)  I would like to know the easiest way (of low complexity) to
    capture a certain length/number of samples (or time period),
    preferably in gnuradio, and then automagically turn off the
    uhd-reception (and save received samples to disk) ?!

    b)  Are there any other (kernel, uhd, gnuradio) buffers and
    settings than "net.core.wmem_max" and "net.core.rmem_max"  (set
    with "sysctl" command in Linux) which affect transmit and receive
    buffering for uhd/gnuradio ?

    Background: I am capturing bursts of samples at very high sampling
    rate (like 25 MSPS @ 16 bit I&Q, or 50 MSPS @ 8 bit I&Q) and save
    them to disk for further offline processing. But for now I have to
    manually cancel the application (CTRL-C) after a few seconds to
    avoid overflow since writing to a normal HDD does not keep up for
    saving in continuos real time (which anyway quickly creates too
    large files). Also, I have tried to maximize receive (and
    transmit) buffering (through mentioned buffers) in order to
    capture (and buffer) as long sequences as possible in RAM before
    saving them to disk and get the inevitable overflows (resulting in
    loss of received samples). However, to avoid overflow without
    manual interception I would like to capture just as much as the
    RAM-buffers can hold (or less) and then automatically turn off the
    reception so that the burst of samples can be saved to disk
    without any overflows and loss of samples.  Feels like it should
    be an easy way to accomplish this but how ?!   FYI: Hardware is
    USRP N210.

    Any help appreciated!

    / Rickard
    Discuss-gnuradio mailing list
    address@hidden <mailto:address@hidden>

Discuss-gnuradio mailing list
You can also use the head block in a custom flowgraph and use some math and knowledge of the sample rate to stop operation after a given time.

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