op25-dev

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314 discussions

Control channel decoding
by Dmitry Medvedev 01 Aug '12

01 Aug '12

I'm writing multichannel p25 recorder. It mostly works (thanks to op25 team and other contributors). Is there any open documentation on control channel messages, especially TSBK frames? I did trellis decoding and CRC algorithm (reverse engineered the later, as I couldn't find parameters). I understand structure of some messages, for example "Group Voice Channel Grant Update" (opcode 02, manufacturer id 00), but many opcodes remain unknown. Do you have any leads on this? Also, I'm not very familiar with gnuradio, is there way to place some kind of "gate" in flowgraph so some parts of it can be switched on/off by external event? I want to use such feature to gate voice channels on/off and do not waste processor cycles on filtering channels that do not carry traffic at the moment. Best regards, Dmitry

4 3

question about frequency correction messages from fsk4 demo
by Stephen 23 Jun '12

23 Jun '12

Hi, I'm trying to do everything in c++ instead of using python. I've got it working. Mostly. Well, sort of. I have a couple of questions about what to do with the frequency correction messages coming from the fsk4demod block. I'm seeing a constant stream of frequency correction messages when there is no signal present. They quickly cause the channel selection filter I'm using to tune way off frequency. If I don't process those messages I get voice output so I know everything else is working. Some channels I tune to seem to work just fine with out needing any tuning. But other times I see transmissions where I don't get any voice output. I'm wondering if in those cases the tuning is needed ? In looking at the grc file it just subtracts the correction. When I look at the uhd_p25_rx_gl.py file it's doing a calculation with the correction and limiting it. Does one method work better than the other? So, does anyone have any suggestions or any idea why I would be getting a constant stream of the messages? thanks, Stephen

1 0

using op25 from c++
by Stephen 19 Jun '12

19 Jun '12

Hi, Is it possible to use the op25 block from c++? I have it built and working with GRC but now I would like to use it from a c++ program. I looked but I could not find a library anywhere? stephen

3 3

Segfault in software_imbe_decoder::decode_spectral_amplitudes
by argilo314 09 Jun '12

09 Jun '12

I was getting segmentation faults whenever starting to decode a P25 signal. (A stack trace is at the bottom of my message.) After a bit of investigating, I found that the value of the OldL variable in software_imbe_decoder was getting used before it was initialized. Adding OldL = 0 to the constructor got rid of the segfaults, but I don't understand the code well enough to know whether it's the correct fix. Regards, Clayton ---------- [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1". Core was generated by `python ./top_block.py'. Program terminated with signal 11, Segmentation fault. #0 0x00007f6e2bcb15a3 in software_imbe_decoder::decode_spectral_amplitudes (this=0x39fa940, Start3=<optimized out>, Start8=<optimized out>) at software_imbe_decoder.cc:1006 1006 for(ell = OldL + 1; ell <= L + 1; ell++) { log2Mu[ell][ Old] = log2Mu[OldL][ Old]; } (gdb) i stack #0 0x00007f6e2bcb15a3 in software_imbe_decoder::decode_spectral_amplitudes (this=0x39fa940, Start3=<optimized out>, Start8=<optimized out>) at software_imbe_decoder.cc:1006 #1 0x00007f6e2bcb305d in software_imbe_decoder::decode_audio (this=0x39fa940, A=<optimized out>) at software_imbe_decoder.cc:913 #2 0x00007f6e2bcb3747 in software_imbe_decoder::decode (this=0x39fa940, cw=...) at software_imbe_decoder.cc:810 #3 0x00007f6e2bc9ea7b in voice_data_unit::do_decode_audio (this=<optimized out>, frame_body=..., imbe=...) at voice_data_unit.cc:50 #4 0x00007f6e2bc98b01 in abstract_data_unit::decode_audio (this=0x7f6dc8000e10, imbe=...) at abstract_data_unit.cc:61 #5 0x00007f6e2bc9ec0a in voice_du_handler::handle (this=0x39fdee0, du=...) at voice_du_handler.cc:45 #6 0x00007f6e2bcad4f8 in op25_decoder_bf::receive_symbol (this=0x39fa4f0, d=2 '\002') at op25_decoder_bf.cc:214 #7 0x00007f6e2bcad980 in op25_decoder_bf::general_work (this=0x39fa4f0, nof_output_items=16, nof_input_items=..., input_items=..., output_items=...) at op25_decoder_bf.cc:86 #8 0x00007f6e31d09ae3 in gr_block_executor::run_one_iteration() () from /usr/local/lib/libgnuradio-core-3.6.1git.so.0.0.0 #9 0x00007f6e31d28d5d in gr_tpb_thread_body::gr_tpb_thread_body(boost::shared_ptr<gr_block>, int) () from /usr/local/lib/libgnuradio-core-3.6.1git.so.0.0.0 #10 0x00007f6e31d23996 in boost::detail::function::void_function_obj_invoker0<gruel::thread_body_wrapper<tpb_container>, void>::invoke(boost::detail::function::function_buffer&) () from /usr/local/lib/libgnuradio-core-3.6.1git.so.0.0.0 #11 0x00007f6e31548a9e in boost::detail::thread_data<boost::function0<void> >::run() () from /usr/local/lib/libgruel-3.6.1git.so.0.0.0 #12 0x00007f6e30eebce9 in thread_proxy () from /usr/lib/libboost_thread.so.1.46.1 #13 0x00007f6e340e2e9a in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0 #14 0x00007f6e32ed44bd in clone () from /lib/x86_64-linux-gnu/libc.so.6 #15 0x0000000000000000 in ?? ()

1 0

problem running usrp_p25_rx.py
by homernighthawk 29 May '12

29 May '12

Hi, I'm having a problem running usrp_p25_rx.py. I've never done anything with op25 before. I followed the build instructions on the wiki at op25.osmocom.org/wiki. I had the same issue that I saw a couple other people post about with adding an include of stddef.h to op25.cc. After that everything built as far as I can tell. I'm using ubuntu 12.04 x64 and gnuradio 3.6 If anyone has any idea what to look at it would be appreciated. thanks, When I try to run usrp_p25_rx.py I get the following error: Traceback (most recent call last): File "./usrp_p25_rx.py", line 727, in <module> app = stdgui2.stdapp(p25_rx_block, "APCO P25 Receiver", 3) File "/usr/local/lib/python2.7/dist-packages/gnuradio/wxgui/stdgui2.py", line 38, in __init__ wx.App.__init__ (self, redirect=False) File "/usr/lib/python2.7/dist-packages/wx-2.8-gtk2-unicode/wx/_core.py", line 7981, in __init__ self._BootstrapApp() File "/usr/lib/python2.7/dist-packages/wx-2.8-gtk2-unicode/wx/_core.py", line 7555, in _BootstrapApp return _core_.PyApp__BootstrapApp(*args, **kwargs) File "/usr/local/lib/python2.7/dist-packages/gnuradio/wxgui/stdgui2.py", line 42, in OnInit self._max_noutput_items) File "/usr/local/lib/python2.7/dist-packages/gnuradio/wxgui/stdgui2.py", line 64, in __init__ self.panel = stdpanel (self, self, top_block_maker, max_nouts) File "/usr/local/lib/python2.7/dist-packages/gnuradio/wxgui/stdgui2.py", line 86, in __init__ self.top_block = top_block_maker (frame, self, vbox, sys.argv) File "./usrp_p25_rx.py", line 75, in __init__ self.__init_gui(frame, panel, vbox) File "./usrp_p25_rx.py", line 252, in __init_gui self.spectrum_plotter = self.spectrum.win.plot AttributeError: 'fft_window' object has no attribute 'plot'

3 2

P25 symbol timing recovery: tone detection method
by ikj1234i 28 May '12

28 May '12

P25 signals modulated using the CQPSK format throw off a loud tone at 4,800 Hz, as shown by a plot of the power spectrum of the signal's magnitude. C4FM-modulated P25 signals do not appear to possess this interesting property. The file in samples 'prwn-d256.dat' appears to be a CQPSK signal with distinctive LSM characteristics. I've uploaded a simple python app which can be used to plot a complex capture sample file - magsq-psd.py. The one non-obvious arg (--calibration) must be used if/as necessary to bring the signal to near zero IF. Note that hardware FM discriminator-tapped receivers cannot be used here since a copy of the signal prior to demodulation is required. A receiver software implementation using the tone detection method can be done using a low-complexity setup such as a DSP CIC filter. Another nice thing is that a tone detection loop works well even when there is some frequency mismatch... Max

2 1

OP25 GRC - Almost but not quite working
by Andy Knitt 21 May '12

21 May '12

I have the OP25 GRC demo that Balint provided up and running. Everything seems to working except I'm not getting any audio out of the OP25 block. I'm getting the "four line" output from the dibit output port when there is traffic on the channel, and the autotune output is outputting data. However, no audio. I put a scope on the audio output and it's a flat line at zero, even when the dibit output is "four lines". Any tips on how to further troubleshoot? Thanks, Andy

12 40

IRC Channel
by Steve Glass 19 May '12

19 May '12

Its been suggested that we start a channel on IRC so we can discuss OP25 and Osmocom stuff. Anybody here an IRC guru? Do we want a channel just for OP25 (which may not have many people in it) or perhaps take part in a potentially larger Osmocom one? What do people think?

3 4

GRC blocks for OP25 and 4FSK missing
by mungewell 15 May '12

15 May '12

Hi all, Just getting started with GnuRadio and RTL2832 so might be missing some details, by following the instructions here: http://op25.osmocom.org/wiki/wiki/BuildInstructionsPage I was able (with a couple of hacks) to built OP25, IMBE and 4FSK - however these did not appear as selectable blocks in GRC. After some time I was able to figure out that they are missing 'xml' definitions in '/usr/local/share/gnuradio/blocks'. Creating a quick/fake '4fsk.xml' made it/something appear. So should these exist? Does anyone have examples of what they should be....? BTW the OP25 which did appear, seems to be from Baz install, not the above instructions. I also experienced problems with build against latest GnuRadio git (seems that 'gruel_common.i' has moved) and the include files are not being installed... other than that things are 'peachy' :-) -- libtool: compile: g++ -DHAVE_CONFIG_H -I. -I../.. -I/usr/local/include/gnuradio -I/usr/local/include -I/usr/include/python2.7 -I ../../../imbe_vocoder/src/lib -g -O2 -Wall -Woverloaded-virtual -pthread -MT _repeater_la-repeater.lo -MD -MP -MF .deps/_repeater_la-repeater.Tpo -c repeater.cc -fPIC -DPIC -o .libs/_repeater_la-repeater.o In file included from repeater.cc:3862:0: rs.h:8:29: fatal error: op25_imbe_frame.h: No such file or directory compilation terminated. make[4]: *** [_repeater_la-repeater.lo] Error 1 make[4]: Leaving directory `/home/simon/op25/repeater/src/lib' make[3]: *** [all] Error 2 make[3]: Leaving directory `/home/simon/op25/repeater/src/lib' make[2]: *** [all-recursive] Error 1 make[2]: Leaving directory `/home/simon/op25/repeater/src' make[1]: *** [all-recursive] Error 1 make[1]: Leaving directory `/home/simon/op25/repeater' make: *** [all] Error 2 simon@drifter:~/op25/repeater$ find .. -name 'op25_imbe_frame.h' ../blocks/src/lib/op25_imbe_frame.h simon@drifter:~/op25/repeater$ find /usr/local/include/ -name 'op25_imbe_frame.h' simon@drifter:~/op25/repeater$ -- Simon

7 10

Building under Ubuntu 12.04 - blocks gives error "op25.cc:3115:13: error: 'ptrdiff_t' does not name a type"
by Richard Clarke 10 May '12

10 May '12

OK I've just upgraded my Ubuntu box to 12.04, from 11.04 (couldn't help myself). I'm trying to rebuild op25 but I'm getting the following error, followed by a string of relate ones (I'm guessing) Compiling blocks: op25.cc:3115:13: error: 'ptrdiff_t' does not name a type A Google search for this kind of error seems to be pointing to stricter typedef requirements by gcc 4.6 with the solution being to include an additional system header file cstddef. However I'm not sure where to include this in the op25 source. I tried putting it in the op25.i swig interface file so that it ends up in the generated op25.cc file however that doesn't appear to have worked. Anyone already solved this or can provide some guidance? Ubuntu 12.04 appears to be using gcc 4.6.3 Thanks Cheers Richard

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