Re: [Discuss-gnuradio] Help decoding Bell 202

[Albin Stigö]

For anyone working with APRS Stephen (wa8lmf) has put together a
downloadable cd image with a lot of test data. Not in quadrature, but
that's maybe something Hilbert can take care of.

http://wa8lmf.net/TNCtest/

# Get it with wget.
$ wget http://www.argentdata.com/files/tnc_test_cd_ver1.0.zip

# Convert the tracks to wave format with the bchunk utility (search
your packet manager or homebrew).
$ bchunk -w TNC_Test_Ver-1.1.bin TNC_Test_Ver-1.1.cue TNC_Test_Ver-1.1.iso


--Albin

On Mon, Dec 28, 2015 at 2:07 AM, En Shih <address@hidden> wrote:
> Thanks, Tim. That really clarified a lot of confusion that I had!
>
> I have uploaded the files here:
> https://drive.google.com/folderview?id=0B5T4PFVUKZgmcXlTWnV0VzZFQTg&usp=sharing
> <https://drive.google.com/folderview?id=0B5T4PFVUKZgmcXlTWnV0VzZFQTg&usp=sharing>
> -"bell202new.grc" is the current flow graph.
> -"dump" is how the input signal I'm trying to decode looks like.
> -"decoded" is the bytes of a successfully decoded signal, which was decoded
> previously using some hardware equipment. (some parts of the data may be
> corrupted)
> -"imet.pdf" explains the data packet.
> -"tcp.py" explains the data packet.
>
> As far as I know, at the physical layer the data is modulated using Bell
> 202. The data framing is not AX.25, but conforms to UART, although I'm
> unsure about the parity and stop bits. I tried looking for the data frames
> by looking for start/stop bits, the header. I've also tried flipping the
> bits. However, it still doesn't look quite right.
>
> Correct me if I'm wrong: your FSK demod block uses tone detection to
> demodulate, which is passing the signal through two band pass filters in
> parallel, and determine which comes through (as in p.9 of
> http://edge.rit.edu/edge/P09141/public/FSK.pdf)
>
> Regards,
> En Shih
>
>
>
>
> --
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> Sent from the GnuRadio mailing list archive at Nabble.com.
>
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