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Re: [Discuss-gnuradio] GSoC: Filter design enhancements progress


From: John Malsbury
Subject: Re: [Discuss-gnuradio] GSoC: Filter design enhancements progress
Date: Tue, 26 Jun 2012 10:49:51 -0700
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.27) Gecko/20120216 Thunderbird/3.1.19

Yes, I know.  Speaking from the standpoint of design flow, it would be helpful if the user doesn't need to touch those lines of code if they'd like to take advantage of the filter designer.

For example, if you could output the co-efficients to a file, and your code calls:

    coeffs = get_coeffs_from_file(my_coeffs_file.csv)

you'd be able to take advantage of the analytical features of the filter designer without modifying your code.  And lets say someday you had a FIR filter hardware.  A custom script might generate a file of a specified format, and the device driver could pick up the file and poke the coefficients.  In short, having the ability to call a custom script allows the user to produce a file of arbitrary format, or do any other arbitrary operation with the coeffecients.

-John



On 06/26/2012 10:27 AM, address@hidden wrote:

John:

Well, there's already gr.firdes, which can be called directly from python, and produce coefficients that can be easily transformed into whatever you need.

Granted, that's only for relatively-simple filters.

from gnuradio import gr

coeffs=gr.firdes.low_pass(1.0,samp_rate,corner_freq,transition_width,widnow,beta)

And then do whatever you want with the resulting coefffs (like scaling to fixed-point 16-bit values, for example)

-Marcus

 

On 26 Jun 2012 13:21, John Malsbury wrote:

That is pretty awesome, Sreeraj.  Is the output of the program a set of co-efficients to be copy-pasted, a compilable block, or something else?  It might be useful to have a feature where the user can call a custom python script with the co-efficients passed as arguments.  This would allow users to easily generate formatted files, like those used by Xilinx coregen or some custom format that might be poked to the FPGA, for example.  It would be neat to make some updates to GRC to allow the user to open the utility and re-generate co-efficients as they do in MATLAB.

This is making me think of some other potential projects, like a similar 'digital modulation designer'.  For example, we might use a single block for all modulation types, select the modulation type and parameters, run simulations to determine BER vs. Eb/N0, theoretical discrete constellations, ACPR, PAR, etc.  Or perhaps, a "packet designer" where you can graphically configure FEC, interleaving, sync words, etc.  Obviously, the complexity on this one could grow real fast.

Just ideas... Hopefully you'll have a chance to present your approach to this at the GNU Radio conference.

-John



On 06/26/2012 09:35 AM, Ben Hilburn wrote:
Sreeraj -
 
I just wanted to echo Tom's thoughts that this look really, really great!  I can't wait to see the final version!  This will really be a significant contribution to the capabilities of GNU Radio, in my opinion.
 
Cheers,
Ben

On Sun, Jun 24, 2012 at 7:05 AM, sreeraj r <address@hidden> wrote:
Hi all,
During the initial phase of SoC, I was concentrating on improving the GUI for filter designing. A brief list of some of the major features added to the filter design tool (gr_filter_design) is given below

--Support for multiple views (grid and old tabbed view)
--Stop-band attenuation configuration via Band-diagram
--Editable pole-zero plots with conjugate movement support
--Impulse, Step responses, phase delay plots 
--Overlay plots

A complete update history along with the code can be found in the github repository(https://github.com/zeroXzero/gr-filtdes). A small video on the current status of the tool can be found here http://www.youtube.com/watch?v=Oi6PTrht1F8&feature=plcp
 
The tool is not completely tested as some more bugs need to be patched. A few more feature additions like add/delete buttons for poles and zeros, alignment of band-diagram, addition of button icons etc are still pending. All these additions will be done with in a few days. In the meantime it would be really helpful if the community can provide feedback in terms of feature additions or bugs so that I can improve the design.
 
After finishing this work I will start working on the actual IIR filter designs as gr-filter has already been merged to the master.
 
---
Regards
Sreeraj Rajendran
http://home.iitb.ac.in/~rsreeraj

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