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Re: [Discuss-gnuradio] usrp over/underrun problems

From: Matt Ettus
Subject: Re: [Discuss-gnuradio] usrp over/underrun problems
Date: Tue, 15 Feb 2005 09:23:34 -0800
User-agent: Internet Messaging Program (IMP) 4.0-cvs

Quoting Bob Vincent <address@hidden>:

> We've got a couple of USRP boards running on "embedded" ebx boards.


> Unfortunately, we are seeing usb overruns/underruns when we run the fsk_tx
> / rx example. I removed the fft from the signal chain, and we still see
> regular overruns on the rx side. Also cut the cordic freq. to 2e6, with the
> same results. I thought this might change the sampling rate. Is that so?

CORDIC freq will not affect sample rate.  You will get the lowest sample rate by
setting the decimator rate to 256.  This will give a sample rate of 64e6/256 =
250 ksamples/sec.

What code are you running?

> Finally, setting the data rate lower seems to make things much worse.
> Perhaps that is because the correlator runs longer?

What correlator?

> We're using fedora 3 on a 1G pentium 3, approximately. I suspect the usb
> isn't fast enough, but that's the hardware we're stuck with. So turning
> down the a/d clock would be good.

Are you certain that this board has USB2?  Most P3's did not have USB2.


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