USRP2 printing of character "S" bothersome!

Hello,
I am using USRP2 version of BBN code to look at AP beacons as seen by
the
USRP2 host. There is lots of “S” printing going on, which keeps me from
reading AP beacon information from STDOUT (unless I save the output to a
file, which I prefer not to). Is there anyway to enforce the printing of
“S”
character to go away. Here is my node’s specification:

My ubuntu version = 10.04
GNuradio version = 3.3.0

Thank you in advance for your help.

cd <gnuradio_repo>/usrp2
find -name “*.cc” | xargs grep ‘“S”’
edit & recompile

-Josh

On 11/11/2010 04:57 PM, Bishal T. wrote:

  • CPU: Intel® Core™ 2 CPU E8400 @ 3GHz
  • Memory: 4GB
  • Hard Disk: 1TB

My ubuntu version = 10.04
GNuradio version = 3.3.0

Keep in mind, though, that those ‘S’ indicate that your host is being
overrun by the USRP2.
An occasional one isn’t a problem, but if you’re getting a lot of
them, it will affect your
Rx performance quite a bit.

I think of an occasional ‘S’ as the same as an occasional “RFI hit” on
the channel. But when
the rate of them gets to the point where you’re losing a significant
amount of Rx data, it’s
a problem.

On Thu, Nov 11, 2010 at 04:57:56PM -0500, Bishal T. wrote:

  • CPU: Intel® Core™ 2 CPU E8400 @ 3GHz
  • Memory: 4GB
  • Hard Disk: 1TB

My ubuntu version = 10.04
GNuradio version = 3.3.0

Thank you in advance for your help.

One of the joys of Free Software is you have the freedom to study how
the program works, and change it to make it do what you wish. We
provide the source code to enable this freedom.

The “S” is written out on line 454 of usrp2_impl.cc

FWIW, it’s written to stderr, not stdout, so you could just shunt
stderr into /dev/null:

$ my-program 2>/dev/null

Eric

On 11/11/2010 05:59 PM, Bishal T. wrote:

“sudo ./bbn_80211b_rx-B.py -f 2.442G -b”
On Thu, Nov 11, 2010 at 04:57:56PM -0500, Bishal T. wrote:
>
>
stderr into /dev/null:
Discuss-gnuradio Info Page

I don’t know anything about the BBN code, but simply switching channels
(frequencies) should have
zero effect on the amount of overruns you are seeing, unless the BBN
code is doing something
different, depending on which channel you’re using, which is possible,
but I don’t know what
it does internally.

Thank you Eric, Josh and Marcus,
I had edited it to print “” nothing. Now, I am shunting it to
/dev/null.

My main reason to ask this question was exactly was Marcus pointed out.
I am
seeing lots and lots of “S”. When I switch channels to 7 or 3, I do see
fewer compared to 6 or 11.
However, I believe something is wrong here.

here is my bbn_80211_rx.py command execution:

“sudo ./bbn_80211b_rx-B.py -f 2.442G -b”

this should mean using barker code and default decimation rate (of 4)
and
samples per baud (25). I am worried now? Could it be just that there are
lots of APs broadcasting few too many beacons?

Thank you once again.