# Capturing DMR (MOTOTRBO) data with gnuradio

**URL:** <https://www.ruby-forum.com/t/capturing-dmr-mototrbo-data-with-gnuradio/243137>\
**Category:** GNU Radio\
**Created:** [August 25, 2015, 8:15am UTC](https://www.ruby-forum.com/t/capturing-dmr-mototrbo-data-with-gnuradio/243137 "2015-08-25T08:15:35Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Rafa\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/958977/32.png) [@Rafa\_F](https://www.ruby-forum.com/u/Rafa_F)\
**Post date:** [August 25, 2015, 8:15am UTC](https://www.ruby-forum.com/t/capturing-dmr-mototrbo-data-with-gnuradio/243137/1 "2015-08-25T08:15:35Z")

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Hello there,

I am trying to capture DMR/MOTOTRBO data packets (not voice) with  
gnuradio.  
I have found gr-dsd block that successfully decodes the signal in  
question.  
Only problem is that gr-dsd does not “unpack” the data packets, it only  
outputs voice audio (float).

All I get from gr-dsd (apart from voice) is output like this (in  
terminal):  
…  
[slot0] slot1 Slot idle  
slot0 [slot1] CSBK  
[slot0] slot1 Slot idle  
slot0 [slot1] CSBK  
[slot0] slot1 Slot idle  
slot0 [slot1] RATE 1/2 DATA  
[slot0] slot1 Slot idle  
slot0 [slot1] CSBK  
[slot0] slot1 Slot idle  
slot0 [slot1] RATE 1/2 DATA  
…

The target system is Ubuntu 14.04LTS (if it makes any difference).  
Another option is not to use gr-dsd, but plainly demodulate the signal  
with  
C4FM/4FSK (for which I am yet to find a stand alone demodulator that  
works  
with current gnuradio), and then cut out the data in “post”.

I have looked at the gr-dsd source and it is way too complicated for my  
skill set to modify it to output data as byte stream.

I have tried to install gr-op25 (just so I can use 4FSK demod block),  
but  
it was way too “heavy” (way too many dependencies).  
I failed to install gr-fsk4 (  
[http://vk2lk.com/Wireless/Franks/GnuradioFourLevelFSK.html](http://vk2lk.com/Wireless/Franks/GnuradioFourLevelFSK.html)), it looks  
like  
it is incompatible with current gnuradio (it fails on missing  
gnuradio-core).

I suspect it is possible to come up with 4FSK demod with just using  
standard gnuradio blocks, my understanding of signal processing is very  
limited…

TL;DR: how can I extract the byte contents out of DMR data packets with  
gnuradio?

Thanks a lot!

Sergei.