Re: [Discuss-gnuradio] need help for digital.constellation_decoder_cb in release 3.5.0

[Ben Reynwar]

On Thu, Dec 8, 2011 at 5:33 PM, Arturo Rinaldi <address@hidden> wrote:
> I noticed dramatic changes in the 3.5.0 release in the generation of the
> constellation points of digital modulations. So, if the easy part is to
> again modify the source code to match my needs, i need some help in using
> the new block :
>
> digital.constellation_decoder_cb(arg1)
>
> instead of
>
> gr.constellation_decoder(arg1,arg2)
>
> I usually used the last one where arg1 is a list containing the complex
> values of a generic digital modulation and arg2 is the symbol mapping (Gray
> Coding for instance). Which blocks do i need to put together to get the same
> result ?
>
> Regards, Arturo
>
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Simplest solution is probably:

constell = digital.digital_constellation(list_of_complex_points, [], 1, 1)
decoder = digital.constellation_decoder_cb(constell)

To get the symbol mapping you want, just choose the appropriate order
of the complex points in the list.

The 2nd, 3rd and 4th arguments to the constellation constructor while
not relevant to this example are:
 - a mapping to be applied before differential encoding.
 - the rotational-symmetry of the constellation
 - the dimensionality of the constellation (i.e. number of complex
points that together map to one symbol)

Functions to simplify the creation of commonly used constellations can
be found in digital.bpsk, digital.qpsk, digital.psk, and digital.qam.

Ben