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Re: [Discuss-gnuradio] trig function in grc variable

From: d.des
Subject: Re: [Discuss-gnuradio] trig function in grc variable
Date: Sun, 02 Jun 2019 16:04:27 +0000
User-agent: Evolution 3.32.2 (3.32.2-1.fc30)

On Sat, 2019-06-01 at 20:16 +0000, d.des wrote:
> I want to add a phase shift block to a grc flowgraph that is
> controlled
> by a scrollbar. Searching for "phase shift block" returns several
> suggestions from several years ago to use the "Multiply Const" block
> with the argument: "math.cos(angle), math.sin(angle)" in the "const"
> field. If I try that I get the error:
> Expression None is invalid for type 'complex'.
> I can enter fixed complex variables or references to other variables
> or
> parameters, I just can't do trig functions. I'm currently using the
> equation: "pow(10,snr/20.)" in a Noise Source block and it
> understands
> that just fine. Is there a way to do trig functions in a block
> field? 
> I'm currently using a clean install and build of gnuradio retrieved
> from git a few days ago, but this issue has been the case for the
> several versions I've retrieved and built over the past year or so. I
> ended up building a hier block with complex_to_magphase, add
> constant,
> and the magphase_to_complex but that seems very inefficient. The
> transcendental function seems to be oriented to streams rather than
> constants that rarely change. I also considered an OOT block but that
> also seems like overkill. Surely I'm missing something really simple.
> The expression should be:
> complex(math.cos(angle-in-radians),math.sin(angle-in-radians))
> >This is standard Python stuff, not specifically related to GRC or
> >Gnu Radio.
> >The assumption is that if you're going to be inserting Python
> >expressions that those expressions
>  > are correct Python expressions.

I completely missed the import block. I don't speak Python and with grc
I usually don't have to. Thanks!

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