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Re: [Discuss-gnuradio] USRP overruns

From: Eric Blossom
Subject: Re: [Discuss-gnuradio] USRP overruns
Date: Sat, 26 May 2007 14:14:45 -0700
User-agent: Mutt/1.5.9i

On Fri, May 25, 2007 at 02:12:26PM +0100, Jonathan Gill wrote:
> Hi all
> We're doing some data collection with the USRP and a basic rx daughter board
> but we're getting those pesky u0 characters appearing.

There's only one place they are output.

> I know that these are generated in response to buffer overruns on the FPGA
> but we are running at pretty low transfer speeds (around 8 Mbyte/s), are
> these same characters used elsewhere in the software to indicate other
> problems - it would be a bit of a bind to find out later that we're looking
> in the wrong place for a problem.

You've probably got a disk throughput and/or latency problem.

If you're running Linux and have the target file system mounted as
ext3, try mounting it as ext2 instead.  Things pretty much die when the
ext3 journal is posted.

If you're running on a laptop, your drive performance is most likely
pretty lame.  Try running on something with a modern 7200 RPM drive.

> We're using a modified version of the usrp_rx_cfile.py script and have two
> inputs to the daughter board going through a single DDC, the problem arises
> on long data collection runs (>10M data points), also were using the (now
> officially deprecated) usrp.source_s
> Thanks for your help
> Jon Gill


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