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Re: [Discuss-gnuradio] Some Basic USRP questions

From: satarkar
Subject: Re: [Discuss-gnuradio] Some Basic USRP questions
Date: Fri, 10 Apr 2009 17:03:58 -0400 (EDT)
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>>>> 1) When I run my scripts I sometimes get "uOuOuO" message. I read in
>>>> the
>>>> archives that I need to increase the decimation rate but I have
>>>> already
>>>> set it to the maximum limit of 256. What should I do? Also, why do I
>>>> not
>>>> get the message all the time?
> Hi,
> A problem I had a while ago was that my operating system (Ubuntu 8.10)
> was throttling my CPU down
> to 800MHz. Have a look in /proc/cpuinfo (or similar) to see your current
> working clock- speed.
> //Mattias
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio

the cpuinfo denotes the speed as 993 MHz.
I am currently following this formula for calculating the interpolation
and decimation rates.

r_tx = r_dac / interp / sps
r_rx = r_adc / decim / sps

Where r_dac is the DAC rate, r_adc is the ADC rate, interp is the
interpolation rate, decim is the decimation rate, and sps is the
samples per symbol. With the values sps = 8, r_dac  = 128e6, r_adc = 64e6
and r_tx = r_rx = 32e3 bps, I get interp = 500, and decim = 250. I use
these interp and decim values when initializing the USRP. I was earlier
using additional software interpolation using a low pass filter, but I
have now removed it.

Can someone please tell me why I still get "uOuOuO" message on both Tx and
Rx ? I am trying to transmit a file and I believe this is the reason it is
not getting received properly.

thanks and regards,

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