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[Discuss-gnuradio] Bug in usrp_rx_cfile.py?

From: John Windish
Subject: [Discuss-gnuradio] Bug in usrp_rx_cfile.py?
Date: Thu, 30 Mar 2006 12:11:01 -0800 (PST)

I think I have found a bug in usrp_rx_cfile.py...

I created an m-file for matlab to format data files that are generated by usrp_rx_cfile.py (attached).  When I process a data file (sample file attached) there is a huge oscillation which occurs at about the 400th sample.

Noting that the data before the oscillation is moving slowly, it looks to me like usrp_rx_cfile.py begins to capture data BEFORE the new parameters for the capture are set-up.  (The capture I did prior to this one had a lower decimation rate, which given my hypothesis on the problem, would give the resultant data).  I'm guessing the huge oscillation occurs when the new parameters are put into effect, and after that, data is captured properly.

Looking through the code, I may be missing an easy way to correct this (if it is indeed the issue).  Has anybody else encoutered an issue similar to this one?

For reference, the data that I attached was captured with a decimation rate of 32 with 20k samples.  The previous capture was done with a decimation rate of 16 and 20k samples.

I'm running Fedora Core 4 on a Pentium based machine.

Thanks for any insight or help. 


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function [Idat, Qdat] = seperate(filenm)

fid = fopen(filenm,'r');
[data,count] = fread(fid,'single');
Idat = data(1:2:length(data));
Qdat = data(2:2:length(data));
subplot(2,1,1); plot(Idat); title('I');
subplot(2,1,2); plot(Qdat); title('Q');

Attachment: N20kD32.dat
Description: 3345016464-N20kD32.dat

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