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RE: [Discuss-gnuradio] Re: FSK now (really) working at 100kbit/sec

From: Deqiang chen
Subject: RE: [Discuss-gnuradio] Re: FSK now (really) working at 100kbit/sec
Date: Fri, 15 Apr 2005 19:38:32 +0000

Thanks, guys!
Now I have another problem about how to use split the dat stream.
I would like to split a data stream, put it into parallel streams and show these streams on screen. Note that I would like to show these data streams together in a single window.
Could any one give me a hint about how I could do that ?
I actually notice there is gr.serial_to_parallel, but the following code


sink, win = scopesink.make_scope_sink_f (self, panel, "Rx Data", input_rate)
       vbox.Add (win, 1, wx.EXPAND)

       self.connect (u,c2f_1)
        self.connect( c2f_1, sp)

produce an error , i.e.,

File "/usr/local/lib/python2.3/site-packages/gnuradio/gr/basic_flow_graph.py", line 114, in connect
   self._connect (points[i-1], points[i])
File "/usr/local/lib/python2.3/site-packages/gnuradio/gr/basic_flow_graph.py", line 119, in _connect
   self._connect_prim (s, d)
File "/usr/local/lib/python2.3/site-packages/gnuradio/gr/basic_flow_graph.py", line 127, in _connect_prim
   self._check_type_match (src_endpoint, dst_endpoint)
File "/usr/local/lib/python2.3/site-packages/gnuradio/gr/basic_flow_graph.py", line 238, in _check_type_match
   raise ValueError, 'source and destination data sizes are different'
ValueError: source and destination data sizes are different

what is wrong with the code ?


From: Eric Blossom <address@hidden>
To: Deqiang chen <address@hidden>
CC: address@hidden
Subject: [Discuss-gnuradio] Re: FSK now (really) working at 100kbit/sec
Date: Fri, 15 Apr 2005 10:41:42 -0700

On Fri, Apr 15, 2005 at 03:37:27PM +0000, Deqiang chen wrote:
> hello, Eric,
> I remembered there is an annoucement that FSK can work at 100kbps.
> So I dig it out and take a look at the source code for the FSK (
> fsk_rx.py) . I am a little surprised
> that there are no time recovery there.

> My understanding is that for fsk, if you use noncoherent
> demodulation, you would not need the phase information.  However,
> you still need to know the timing in order to correctly sampling the
> output of correlator or matched filter.  Could you give a hint of
> what is going on here ?

> david

The output rate of gr.quadrature_demod_cf is 8 times the symbol rate.
The selection of the center of the bit is done in gr.simple_correlator.
It watches for a pseudo random sync pattern at the beginning of
each packet and uses this to figure out which of the possible alignments
is best.  A similar technique is used in Bluetooth.


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