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Re: [Discuss-gnuradio] USRP2 Simultaneous Tx and Rx Transmit Errors

From: Eric Blossom
Subject: Re: [Discuss-gnuradio] USRP2 Simultaneous Tx and Rx Transmit Errors
Date: Tue, 7 Apr 2009 12:18:45 -0700
User-agent: Mutt/1.5.18 (2008-05-17)

On Wed, Mar 25, 2009 at 01:13:32PM -0700, Johnathan Corgan wrote:
> 2009/3/25 Kyle Pearson <address@hidden>:
> > When I try to simultaneously transmit and receive a sine wave source
> > on one USRP2 using GRC, there appear to be phase discontinuities in
> > the transmitted waveform(as if packets from the computer to the usrp2
> > for transmit are possibly being lost or garbled). This only occurs
> > when transmitting and receiving at the same time, and when I connected
> > the tx signal to a spectrum analyzer it showed random spurs in
> > addition to the expected peak from the signal. When only transmitting
> > the output on a spectrum analyzer confirms that the transmits properly
> > and when receiving a signal from a signal generator there are no
> > errors. This occurred even when the decimation and interpolation rate
> > was set to 512 and I tried a different ethernet cable but the problem
> > still persists.


Matt made some changes in the USRP2 FPGA and firmware code in
changeset 10762 that we believe fixes this problem.

Can you please download and try the lastest FPGA image and firmware
from http://gnuradio.org/releases/usrp2-bin/trunk and let us know if
this fixes it for you.

FYI, at high data rates, full-duplex, the firmware becomes a
bottleneck and will limit the maximum reliable throughput
achievable.  Fixing that will most like require moving at least some
of the state machine that's currently implemented by firmware into the
FPGA fabric.


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