How to turn-off TX of UHD sink in gnuradio companion?

GNU Radio
1

Hi –

I just got my USRP B200. I’m able to receive and transmit with it. It is
very nice!
I have one issue. In gnuradio-companion I pipe an FM modulated signal
into
UHD sink with the TX/RX output.
I would like to have a button that turns the TX off to allow RX on the
same
port. I can not find a way to do that within gnuradio-companion. Anybody
has
an idea?

My workaround right now is to turn the transmit gain down, and change
the
center frequency of the transmit away while receiving in RX2 port. This
is a
“full duplex” mode, but I would really like a half-duplex on the RX/TX.

Thanks!

– Miki

–
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2

On Wed, Dec 4, 2013 at 3:37 AM, mlustig [email protected] wrote:

My workaround right now is to turn the transmit gain down, and change the
center frequency of the transmit away while receiving in RX2 port. This is a
“full duplex” mode, but I would really like a half-duplex on the RX/TX.

Thanks!

– Miki

One easy way is to use the mute block and have it controllable from a
check box GUI element.

Tom

3

On 12/04/2013 09:46 AM, Tom R. wrote:

One easy way is to use the mute block and have it controllable from a
check box GUI element.

Tom

Unless the mute block causes an EOB tag to be sent downstream to the UHD
sink, that won’t have the desired effect.

When doing half-duplex, sharing a common RF port, the USRP needs to know
when you’ve ended a “burst”, so that it can
switch the antenna port between the RX and TX. And again when you
start transmitting, it’ll need a SOB tag to cause
the TX state machine to wake-up.

The usual mode implemented by gr-uhd is continuous streaming on TX.

–
Marcus L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium

4

I see,…interesting.

So how do you send an SOB tag within gnu radio companion?
I’m new to this and could not find any documentation on grc that made
sense to me.

– Miki, KK6MRI, from mobile

5

On 12/04/2013 10:49 AM, Michael Lustig wrote:

I see,…interesting.

So how do you send an SOB tag within gnu radio companion?
I’m new to this and could not find any documentation on grc that made sense to
me.

– Miki, KK6MRI, from mobile
There’s a burst-tagger block:

http://gnuradio.org/doc/doxygen/classgr_1_1blocks_1_1burst__tagger.html

I can’t for the life of me remember how to form the SOB/EOB tags that
UHD needs. But perhaps someone who has actually used the EOB/SOB stuff
could chime in.

–
Marcus L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium

6

I tried the Burst Tagger block. Reading on-line it seems that the key
tags should be tx_eob and tx_sob

I implemented this way:

I can see the Tags in the stream using Tag debugger, but nothing is
happening to the UHD sink which keeps transmitting.

Anybody?

Thanks,

– Miki

On Dec 4, 2013, at 8:04 AM, Marcus D. Leech [via GnuRadio]
[email protected] wrote:

http://www.sbrac.org
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