# Asking help about gr-ieee802.11 **URL:** \ **Category:** GNU Radio\ **Created:** [July 6, 2015, 5:17am UTC](https://www.ruby-forum.com/t/asking-help-about-gr-ieee802-11/242591 "2015-07-06T05:17:30Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Detlef\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/58f4c7/32.png) [@Detlef\_R](https://www.ruby-forum.com/u/Detlef_R)\ **Post date:** [July 6, 2015, 5:17am UTC](https://www.ruby-forum.com/t/asking-help-about-gr-ieee802-11/242591/1 "2015-07-06T05:17:30Z")
hi. I am newbie of gnuradio.i try run wifi\_loopback.grc, all the port are connected.but when i run it comes out with this messege below: Generating: “/home/user/gr-ieee802-11/examples/wifi\_loopback.py” > > > Warning: This flow graph may not have flow control: no audio or RF hardware > > > blocks found. Add a Misc-\>Throttle block to your flow graph to avoid CPU > > > congestion. Executing: “/home/user/gr-ieee802-11/examples/wifi\_loopback.py” linux; GNU C++ version 4.8.2; Boost\_105400; UHD\_003.009.git-171-g51bc00ee Using Volk machine: avx\_64\_mmx\_orc OFDM MAPPER: encoding: 0 set\_min\_output\_buffer on block 31 to 96000 set\_min\_output\_buffer on block 33 to 96000 set\_min\_output\_buffer on block 35 to 96000 set\_min\_output\_buffer on block 36 to 96000 set\_min\_output\_buffer on block 39 to 96000 set\_min\_output\_buffer on block 50 to 96000 > > > Done (return code -11) below is my system info: user@userr-X455LDB:~$ python -V Python 2.7.6 user@userr-X455LDB:~$ gnuradio-config-info -v 3.7.7.1 user@userr-X455LDB:~$ uname -a Linux userr-X455LDB 3.13.0-53-generic #89-Ubuntu SMP Wed May 20 10:34:39 UTC 2015 x86\_64 x86\_64 x86\_64 GNU/Linux user@userr-X455LDB:~$ gcc --version gcc (Ubuntu 4.8.2-19ubuntu1) 4.8.2 Copyright © 2013 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. user@userr-X455LDB:~$ cat /etc/lsb-release DISTRIB\_ID=Ubuntu DISTRIB\_RELEASE=14.04 DISTRIB\_CODENAME=trusty DISTRIB\_DESCRIPTION=“Ubuntu 14.04.2 LTS” what can i do? i hope you can help me. thanks ---
**Author:** ![fie](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/f9ae1b/32.png) [@fie](https://www.ruby-forum.com/u/fie)\ **Post date:** [July 6, 2015, 6:23am UTC](https://www.ruby-forum.com/t/asking-help-about-gr-ieee802-11/242591/2 "2015-07-06T06:23:33Z")
Hi Nur, the actual error message is not shown in your output. I think you should run the flow graph in gdb with something like gbd python gdb-prompt\> run /home/user/gr-ieee802-11/examples/wifi\_loopback.py once you hit the error gdb-prompt\> bt Best, Bastian > set\_min\_output\_buffer on block 36 to 96000 > 3.7.7.1 > > Discuss-gnuradio mailing list > [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > [Discuss-gnuradio Info Page](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio) – Dipl.-Inform. Bastian B. Distributed Embedded Systems Group University of Paderborn, Germany > **[Home](https://www.bastibl.net/)** > > I'm Bastian Bloessl, a Research Group Leader at the Secure Mobile Networking Lab, TU Darmstadt. Checkout my blog, projects, publications, and resume; or connect on Github, Twitter, YouTube, or Facebook. ---
**Author:** ![fie](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/f9ae1b/32.png) [@fie](https://www.ruby-forum.com/u/fie)\ **Post date:** [July 6, 2015, 7:35am UTC](https://www.ruby-forum.com/t/asking-help-about-gr-ieee802-11/242591/3 "2015-07-06T07:35:47Z")
user@userr-X455LDB:~$ /home/user/gr-ieee802-11/examples/wifi\_loopback.py linux; GNU C++ version 4.8.2; Boost\_105400; UHD\_003.009.git-171-g51bc00ee Using Volk machine: avx\_64\_mmx\_orc OFDM MAPPER: encoding: 0 set\_min\_output\_buffer on block 31 to 96000 set\_min\_output\_buffer on block 33 to 96000 set\_min\_output\_buffer on block 35 to 96000 set\_min\_output\_buffer on block 36 to 96000 set\_min\_output\_buffer on block 39 to 96000 set\_min\_output\_buffer on block 50 to 96000 Segmentation fault (core dumped) ---
**Author:** ![fie](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/f9ae1b/32.png) [@fie](https://www.ruby-forum.com/u/fie)\ **Post date:** [July 6, 2015, 7:54am UTC](https://www.ruby-forum.com/t/asking-help-about-gr-ieee802-11/242591/4 "2015-07-06T07:54:41Z")
Dear Nur, it would be very helpful if you could wrap you console output into one or two sentences describing what you did. I have no idea where the error message comes from and would suggest you go to /home/user/gr-ieee802-11/ and do a git reset --hard then open examples/wifi\_phy\_hier.grc and build it. Then open examples/wifi\_loopback.grc and run it. Best, Bastian ---
**Author:** ![fie](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/f9ae1b/32.png) [@fie](https://www.ruby-forum.com/u/fie)\ **Post date:** [July 9, 2015, 4:28am UTC](https://www.ruby-forum.com/t/asking-help-about-gr-ieee802-11/242591/5 "2015-07-09T04:28:57Z")
(gdb) run /home/user/gr-ieee802-11/examples/wifi\_loopback.py Starting program: /home/user/gr-ieee802-11/examples/wifi\_loopback.py No executable file specified. Use the “file” or “exec-file” command. (gdb) bt No stack. what can i do?i hope you can help me. ---
**Author:** ![fie](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/f/f9ae1b/32.png) [@fie](https://www.ruby-forum.com/u/fie)\ **Post date:** [July 6, 2015, 8:38am UTC](https://www.ruby-forum.com/t/asking-help-about-gr-ieee802-11/242591/6 "2015-07-06T08:38:44Z")
Preferences file: /home/user/.grc Block paths: /usr/local/share/gnuradio/grc/blocks /home/user/.grc\_gnuradio Loading: “/home/user/gr-ieee802-11/examples/wifi\_phy\_hier.grc” > > > Done Showing: “/home/user/gr-ieee802-11/examples/wifi\_phy\_hier.grc” Generating: “/home/user/.grc\_gnuradio/wifi\_phy\_hier.py” Generating: “/home/user/.grc\_gnuradio/wifi\_phy\_hier.py” Executing: “/home/user/.grc\_gnuradio/wifi\_phy\_hier.py” > > > Done