[op25-dev] Re: GRC blocks for OP25 and 4FSK missing

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rrgsti bobrich at gmail.com
Thu May 10 15:50:35 UTC 2012

Hi there,

AFAIK, the OP25 components do not show up in GRC.  As you've found, gr-baz includes an OP25 block for GRC that encapsulates OP25 functionality.  Balint also provided an example flowgraph that uses it, so you generally just need to tweak the frequency. 

I'm having difficulty successfully decoding P25 with my RTL2832, so I'm very interested in your results.  If you get no audio output whatsoever, take a look at the 'not quite' thread in here as well.  I modified data_unit.cc to force all frames to be detected as LDU1 (voice), which is 100% broken, but I do get chunks of audio.

I also ran into the same issue with compilation.  If you punch 'op25_imbe_frame.h' into the search function in this group you'll find a couple threads with fixes.

Last but not least, there is a discussion today on the rtlsdr subreddit about sampling rates.  In short, ensure that your sampling rate is an even divisor of 28.8, such as 2.4 or 1.8msps, or you may get some artifacts in the signal.

Good luck!

--- In op25-dev at yahoogroups.com, "mungewell" <simon at ...> wrote:
> 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 at drifter:~/op25/repeater$ find .. -name 'op25_imbe_frame.h'
> ../blocks/src/lib/op25_imbe_frame.h
> simon at drifter:~/op25/repeater$ find /usr/local/include/ -name
> 'op25_imbe_frame.h'
> simon at drifter:~/op25/repeater$
> --
> Simon

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