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RE: [Discuss-gnuradio] Trouble with gr_costas_loop_cc

From: Tom Rondeau
Subject: RE: [Discuss-gnuradio] Trouble with gr_costas_loop_cc
Date: Tue, 15 Aug 2006 13:52:17 -0400

That's probably mostly due to a versioning problem. The reference phase
argument is no longer used. What the Costas loop is expecting, instead, is
(alpha, beta, max_freq, min_freq, order). The order is the order of the
Costas loop. Use 2 for BPSK and 4 for QPSK. This determines how the slicer
behaves on the incoming data (whether to lock to 2 phase reference points or

Look at the examples in gnuradio-examples/python/gmsk2, specifically the
benchmark_mpsk_tx.py, or more specifically, bpsk.py.

Speaking of which, the [d]<m>psk.py files are pretty stable as they are now
(though they need a bit more work) and can probably be placed in the core
code with gmsk.py.


> -----Original Message-----
> From: address@hidden [mailto:discuss-
> address@hidden On Behalf Of
> address@hidden
> Sent: Tuesday, August 15, 2006 1:25 PM
> To: address@hidden
> Subject: [Discuss-gnuradio] Trouble with gr_costas_loop_cc
> Hello,
> I am working on demodulating a BPSK signal (a manchester coded stream of
> pseudorandom bits.)  I'd like to use a gr_costas_loop_cc block to recover
> the carrier.  However, when I try to create the block with all five args
> (alpha, beta, max_freq, min_freq, and ref_phase) as floats, python returns
> the following:
> " TypeError: argument number 5: a 'long' is expected, 'float(0.1)' is
> received "
> where 0.1 is the value assigned to ref_phase, the fifth parameter.
> If I make ref_phase=0, then the error returned by python is:
> " RuntimeError: std::invalid_argument "
> In both cases, error appears to originate from costas_loop_cc in
> gnuradio_swig_python.py.  Source code for gr_costas_loop_cc indicates that
> it definately wants all floats, so why is expecting a long for the fifth
> parameter?
> Any feedback on this would be greatly appreciated!
> Best regards,
> Jon
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