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Re: [Discuss-gnuradio] Converting complex-short to complex-float with UH

From: Almohanad Fayez
Subject: Re: [Discuss-gnuradio] Converting complex-short to complex-float with UHD
Date: Mon, 12 Sep 2011 13:28:35 -0400 (EDT)

I want to use COMPLEX_INT16 in hopes of generating non-normalized fixed point data using UHD.  I ultimately want to send this data over to the DSP on the E100, if I receive the data as COMPLEX_FLOAT32 then UHD is performing

fixed-point -> floating point  and I will be performing floating-point -> fixed-point
-> floating-point feeding into the FPGA.  Ultimately I want

FPGA ->fixed-point -> DSP -> fixed-point -> FPGA

instead of

FPGA ->fixed-point -> floating-point -> fixed_point -> DSP -> fixed-point -> floating-point -> fixed-point -> FPGA

however in my flowgraph I want to be able to use gr.probe_avg_mag_sqrd() and a scalar multiples before feeding into the DSP and it fails when I use  COMPLEX_INT16 because of data type confusion

al fayez

-----Original Message-----
From: Josh Blum <address@hidden>
To: discuss-gnuradio <address@hidden>
Sent: Mon, Sep 12, 2011 1:18 pm
Subject: Re: [Discuss-gnuradio] Converting complex-short to complex-float with UHD

On 09/12/2011 10:00 AM, Almohanad Fayez wrote:
> I can't seem to find a direct way of typcasting COMPLEX_INT16 using
> gr-uhd as complex_float. It seems that gnuradio assumes that a
> complex type is composed of floats by default which causes issues
> when I'm using gr-uhd, is there a direct way to do complex_short to
> complex_float conversion or should I just make a custom block for
> that? thanks.

The output signature for COMPLEX_INT16 is a vector of shorts length 2.
You can covert this to complex float with a vector_to_stream block, and
then a ishort_to_complex block.

BTW, if you want complex floats, it makes way more sense to just use
COMPLEX_FLOAT32. The real use of COMPLEX_INT16 is if you have a block
that produces or consumes complex shorts. Otherwise its just extra overhead.


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