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Re: [Discuss-gnuradio] TX/RX simultaneously using one USRP board


From: David Scaperoth
Subject: Re: [Discuss-gnuradio] TX/RX simultaneously using one USRP board
Date: Thu, 13 Apr 2006 19:39:37 -0400

Hey dawei,

I just recently played with the idea of a repeater (receive on frequency and transmit on another).  ALthough I have personally only used the TvRx and Basic Tx, the concept is basically the same (I would imagine) for the FLEX400.  I haven't pushed the data rates, but for narrowband FM, it works great.  I guessing the only bottleneck might be the USB (8MSps total), but I like I said, I haven't tested it.  Here was my basic flow graph.  It worked like a charm.

dst = usrp.sink_c (0, tx_interp) 
self.rx_src = usrp.source_c (0, decim)

self.connect (self.rx_src, rx_amp, fm_demod)
self.connect (fm_demod,rx_filter)
self.connect (rx_filter,tx_filter)
self.connect (tx_filter,freq_mod)
self.connect (freq_mod,tx_amp,dst)

So, essentially the key points are that you can use the usrp as both a sink and source (its duplexing baby!).  The underlying code selects the most likely subdevice (if you don't do that yourself), so its pretty easy really.  and where I usually have a sink to a file, audio card, or whatever (for a receiver chain), I just simply use that as the source for my normal transmit.  Here's a link to the source code, I haven't spent any time making it look pretty, but it should work.  I hope this helps some!  Good Luck!

http://www.filebox.vt.edu/~scaperot/FM_Rx_Tx_tvrx.py

David Scaperoth

On Apr 13, 2006, at 1:47 PM, Dawei Shen wrote:

Hi, Eric and other friends

Now I am working on a project that requires simutaneous TX/RX within
one usrp board. I equip too FLEX400 daughter cards on one USRP board.
What I am trying to do is to use the TX to retransmit (i.e. relay)
what the USRP has received from the RX. Is it doable under the current
framework of GNU Radio? If so, could you provide any hints on how to
realize this? An obvious question to me is that in the Python code, we
should either define the usrp as a source or a sink, but in my
application, the USRP board serves as both sink and source. So what
should I do in my case?

Thank you for your input

Dawei
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