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

[Robert Miller]

Guys,
Thanks for your help.  I think my best path forward is to modify the
usrp_nbfm_ptt.py code and use set_enable.  My intended application requires
the reuse of the same antenna for TX and RX.  My data is not packetized (it
is simply tones to begin with), so it seems the easiest path forward.  My
end goal is to transmit and receive between 2 RFX daughterboards using only
the RX/TX ports in a time-multiplexed fashion (see post "TX/RX
Coordination").  Step one will be to perform the switching based on
space-bar depression, but eventually I'd like to incorporate a system timer
for this functionality.
Thanks again,
Rob


Michael Dickens-2 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.
> 
> 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.
> 
> 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.
> 
> Thus, if your application can be easily packetized, then the use of  
> "auto_tr" is warranted.  Otherwise, either use different antennas or  
> manually switch the USRP_TX object on and off.
> 
> 
> 
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