Re: [Discuss-gnuradio] RDS decoding ?

[Kevin McQuiggin]

Hi Jean-Michel:

Certainly!  It took me a couple of months of reading, experimentation and 
head-scratching to figure the DSP side of RDS reception out.  I had a bit of 
help from a couple of people on the [discuss-gnuradio] list as well.

The GRC is at home, I will post it to the list (or a pointer to it) when I get 
back from my outing this morning.  I am a newbie though, so I am sure that the 
experts on the list will find several improvements.

Like hardware radio, I find it very interesting that there can be several “ways 
to do it” for a particular problem.

You will find that the next challenge, after you get the RDS data side working, 
is to write the program that does the group detection, then frame 
synchronization, error detection, and data extraction.  I wrote my program in 
C, and it is about 1000 lines of code.  I started small and built it up from 
there.  Currently it is working very well for several types of RDS frame.

I was in SE Asia on holiday for a few weeks with my wife and was able to use 
the time to develop most of this code.  That’s MY kind of vacation!

I use a TCP Sink in GRC to deliver the RDS data from the flowgraph to the C 
program.  The C program opens a socket and reads the data stream from it.  
Terminal output is through the ncurses package.

You will need to read about the RDS spec both for the flowgraph (physical 
layer) and for the data interpretation.  I used the official RDS/RBDS 
specification document to develop my code.  I will send you a link to it as 
well.

For this stage, I would recommend checking out the work done by Oona Räisänen.  
Her web site is http://www.windytan.com, and she has several informative posts 
about RDS.

Kevin

> On Jan 10, 2016, at 4:45 AM, Jean-Michel FRIEDT <address@hidden> wrote:
> 
> I have just read on the gnuradio mailing list that you completed RDS
> decoding. I too am stuck after extracting the 3*19 kHz carrier and mixing
> with the original WBFM output to get the RDS stream at baseband. I am not sure
> how to run the BPSK demodulator: would you mind sharing your grc graph so I
> can also complete the demodulation ?
> 
> Thanks, Jean-Michel
> 
> --
> JM Friedt, FEMTO-ST Time & Frequency/SENSeOR, 26 rue de l'Epitaphe, 25000 
> Besancon, France
> 
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