On 02/26/2012 08:54 PM, George Nychis wrote:
On Sun, Feb 26, 2012 at 5:01 PM, Marcus
D. Leech
<address@hidden>
wrote:
On 02/26/2012 02:29 PM, Apurv Bhartia
wrote:
Its an XCVR2450, but I do *not*
start any 'packet' transmissions. All I do, is to start
both the flowgraphs, and just listen for packets.
In which case, the TX side is running--even if you aren't
sending any *data* bits, it's still transmitting, and
blocking the receiver.
You'll have to get more sophisticated about half-duplex flow
management, using tagging to tell UHD to turn on/off the TX
side.
Josh probably has better words of wisdom on this than I.
Hi Marcus,
I'm working with Apurv, so I'm going to chime in here :)
I tried doing some searching on the mailing list, but I
wasn't really able to find much on this. I also thought that
auto tr would handle this. I found a post from Josh on the
mailing list that said Auto TR is always enabled in UHD.
Yes, it is enabled in UHD. But since Gnu Radio is a *streaming*
model, you need to take special measures to control TX from within a
Gnu Radio flow-graph. YOu need to insert a tag in the stream to
control the transmitter, otherwise, you'll be continuously
streaming.
What you do is insert a burst-tagger into your stream, and set it to
send the appropriate tags for UHD into the stream using the trigger
input. I just can't off the top of my head, remember what those
stream tags are at the moment. But the basic issue is that Gnu
Radio
uses a streaming model, and while UHD itself (at the C++ level)
has fine-grianed control over transmitter functions, etc, gr-uhd
doesn't
directly expose any of that, because there's just not mechanism
within Gnu Radio to expose that stuff. The stream tagging, however,
does allow you to control the transmitter state. In the
particular case of the XCVR2450, the hardware is physically
incapable of
TX and RX at the same time.
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org