Re: [Discuss-gnuradio] set_auto_tr(), gr_stall, and PTT

[Matt Ettus]

Michael Dickens wrote:
> On Dec 29, 2007, at 4:03 PM, Matt Ettus wrote:
> > Your message stated you wanted to do "simultaneous TX/RX".  If you 
> > want to switch back and forth, then you do not want simultaneous, 
> > which is a good thing.  You want to use the auto t/r switching mode.
>
>
> Just to clarify, and IIRC so please correct:
>
> The "auto_tr()" mode works as follows: If -nothing- is on the TX 
> stream on the USRP hardware (e.g. data is stalled, by whatever means), 
> then RX will happen.  If -anything- is going across USRP TX hardware 
> (e.g. all 0's, your desired signal, whatever), then TX will happen.

yes

> The best way to make use of "auto_tr()" is via packets, not streams 
> ... thus my comment about not yet trying out a "gr_stall" block for 
> streaming, since I haven't really tried "packets" yet.

I guess that would be correct

> Given my PPT example, it makes more sense to use half-duplex on 1 
> antenna (not auto_tr), or full-duplex on 2 antennas (not auto_tr), 
> rather than try to packetize the data stream to make use of auto_tr.

No, I would use auto_tr on 1 antenna.  When there is nothing being sent 
on TX, it will receive.  Just send a stream to the TX when you want to talk.

Matt