Re: [Discuss-gnuradio] tuning while acquiring data

[Eric Blossom]

On Fri, May 08, 2009 at 03:43:34PM -0400, Andrew Lutomirski wrote:
> Hi all-
> 
> I'm trying to re-tune a daughterboard, while acquiring samples, and I
> seem to get an overrun every time.  (This is in C++.)

> Before I start investigating really hackish ways to make this work,
> has anyone had any success getting this to work?

I'm assuming this is on a USRP2.

The current firmware stops the streaming, does the tune, and restarts
streaming.  This produces a discontinuity of varying length, but
doesn't underrun.

Latest versions of the FPGA and firmware:

  http://gnuradio.org/releases/usrp2-bin/trunk/txrx_edk10.1_r10925.bin
  http://gnuradio.org/releases/usrp2-bin/trunk/u2_rev3_ise10.1sp3_r10766.bin


> I don't actually care about the data I get while tuning, but I don't
> want to lose track of the exact time, so I'd be happy with a way to
> ask the USRP to pause for a specified number of samples, as well, or
> even just to know how many samples I lost due to the overrun.

If you're using the libusrp2 interface, you can check the timestamp in
the metadata passed to your rx_sample_handler.

If you're using the usrp2_source_* interface there's currently no way to
know.  This will be possible when we implement the "stream annotation"
feature.

Eric