Re: [Discuss-gnuradio] Decoding FSK modulated signal

[Michael Ossmann]

On Mon, Apr 14, 2014 at 01:25:48PM +0200, Andre Puschmann wrote:
>
> Attached is a screenshot of a GRC waveform I used to capture the
> preamble of a single packet. Channel 2 is simply the output of a
> quadrature demod block connected to a scope GUI block. I'd like to
> decode that into a sequence of bits to run preamble detection etc.
> 
> I've seen a few OOT modules that do similar stuff but was wondering if
> there is a GR'ish way to this, maybe a set of generic blocks that
> could be used for that?

It looks like you are on the right track!  For the next steps, I
recommend a low pass filter (with perhaps 20 kHz cut-off) followed by
M&M clock recovery and binary slicer.  Check out the recent "ASK
demodulation help" thread for more details.  Try setting the decimation
of the LPF to something that gives you 2 to 5 samples per symbol.

Your graph looks like the preamble is at about 1.92 kbps, not 19.2 kbps,
so I suspect that you have an error somewhere in your sample rate
configuration.

Mike