Re: [Discuss-gnuradio] How to capture the Rx data using uhd_rx_cfile and agree with the uhd_fft Scope mode data

[Josh Blum]

On 09/25/2012 07:29 PM, LD Zhang wrote:
> Hello community,
> 
> I am trying to use the uhd_rx_cfile command to capture some rx samples in
> the hope of recovering what I see as streaming samples in the uhd_fft Scope
> mode display. Since I am really new to GR+USRP, I have a couple of
> difficulties:
> 
> 1. The uhd_rx_cfile command help menu does not provide a BW option
> 2. When using the uhd_rx_cfile command and specifying a frequency, it seems
> to record a sinusoid, again possibly a bw issue. However, I am not quite
> sure whether I am looking at the same signal port input. I intend to look
> at LFRX daughter board port B input.
> 3. I have not been able to reproduce what I saw in the uhd_fft Scope mode
> streaming data. Without any gain, I am seeing streaming data at a level of
> +/- 200 units, which may be reasonable noise. How do I capture the same
> data into a file. Since my difficulty with "uhd_rx_cfile" command, hence
> this question. I have also experimented with the "rx_samples_to_file"
> command with worse experience.
> 
> I could go directly to GRC GUI directly and try to learn to do everything
> there. But I think there is value in being able to do this simple thing
> from the command line. Your help and suggestions are appreciated.
> 

I will second this motion.

All of the hooks are available in the USRP source block, most of which
can be changed at runtime with a simple variable widget. Its nice to
change setting at runtime to see the effect.

Also, you can easily attach a file sink and a scope sink and an fft
sink. That way you know that you have captured to file the same thing
you are observing.

Also, be careful with the format of the file data. Its a binary array of
std::complex<float>, not float, not double, etc...

-josh

> LD Zhang
> 
> 
> 
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