[USRP-users] Full Duplex vs. Half Duplex operation?

Radio User radiogeek381 at gmail.com
Thu Oct 23 20:32:53 EDT 2014



Posting to the list was the key to finding the solution.

Apparently, libuhd/FPGA determines that we are in "full duplex" mode when
there is an
active (that is to say, extant) tx_streamer alive at the same time we have
an extant rx_streamer.
It doesn't matter if anything is being set to the streamer, its mere
existence (along with
an rx_streamer) will trigger the condition.

As you said, the ATR (automatic-transmit-receive) switch in the GPIO
register is pretty
smart.  If you are in full dux, it won't connect the RX input to the TX
output, because
bad things will happen.  So, to build a transceiver that uses the TX/RX
port for the antenna,
one needs to destroy any active tx_streamers while in RX mode, and recreate
the streamer
before initiating a new transmission.

So, the rule is:

foo = usrp->get_tx_stream(stream_args);

creates a streamer.  The radio will be in the ATR_REG_FULL_DUPLEX (if there
an rx_streamer in existence) or ATR_REG_TX_ONLY (if not.)
destroy the tx_streamer
(like this?)  foo->~tx_streamer();  // I'm sure there is a better way
and the mode is either ATR_REG_RX_ONLY (if an rx_streamer is alive) or


The key to finding something yourself is to ask someone else where it

On Thu, Oct 23, 2014 at 7:47 PM, Ian Buckley <ianb at ionconcepts.com> wrote:

> ---- snip -----
> The gist of this is that in your case either: a) For some reason the
> ATR-GPIO has not been programmed by UHD to select the correct SMA or b) The
> USRP is not in the state you think it is (RX vs Full-Duplex)
> Make sense?
> -Ian
> On Oct 23, 2014, at 4:10 PM, Radio User via USRP-users <
> usrp-users at lists.ettus.com> wrote:
> Fellow USRPers..
> ---- snip ----
> rg
> _______________________________________________
> USRP-users mailing list
> USRP-users at lists.ettus.com
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
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