# How to use constellation decoder

**URL:** <https://www.ruby-forum.com/t/how-to-use-constellation-decoder/235502>\
**Category:** GNU Radio\
**Created:** [June 25, 2013, 9:46pm UTC](https://www.ruby-forum.com/t/how-to-use-constellation-decoder/235502 "2013-06-25T21:46:07Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![alcina](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/a587f6/32.png) [@alcina](https://www.ruby-forum.com/u/alcina)\
**Post date:** [June 25, 2013, 9:46pm UTC](https://www.ruby-forum.com/t/how-to-use-constellation-decoder/235502/1 "2013-06-25T21:46:07Z")

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Hi,

I am struggling to use the constellation decoder. I saw this post, but  
it  
does not work for me.

[http://gnuradio.4.n7.nabble.com/Constellation-Decoder-GRC-Help-td36508.html#a34137043](http://gnuradio.4.n7.nabble.com/Constellation-Decoder-GRC-Help-td36508.html#a34137043)

> > > from gnuradio import digital  
> > > digital.constellation\_decoder\_cb(digital.constellation\_bpsk())  
> > > Traceback (most recent call last):  
> > > File “”, line 1, in   
> > > File  
> > > “/usr/local/lib/python2.7/dist-packages/gnuradio/digital/digital\_swig.py”,  
> > > line 4864, in constellation\_decoder\_cb  
> > > return \_digital\_swig.constellation\_decoder\_cb(\*args, \*\*kwargs)  
> > > TypeError: in method ‘constellation\_decoder\_cb’, argument 1 of type  
> > > ‘digital\_constellation\_sptr’

Any help would be appreciated, I am using GNURadio 3.6.5.

Regards,

Stephen

---

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**Author:** ![Stephen\_Harrison](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/45deac/32.png) [@Stephen\_Harrison](https://www.ruby-forum.com/u/Stephen_Harrison)\
**Post date:** [June 25, 2013, 11:15pm UTC](https://www.ruby-forum.com/t/how-to-use-constellation-decoder/235502/2 "2013-06-25T23:15:32Z")

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On Tue, Jun 25, 2013 at 3:44 PM, Stephen Harrison  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> File “”, line 1, in
> 
> Stephen

Try this

python\> from gnuradio import digital  
python\>  
digital.constellation\_decoder\_cb(digital.constellation\_bpsk().base() )

The base method returns the digital\_constellation\_sptr that  
constellation\_decoder\_cb is expecting.

-Nathan