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Re: [Discuss-gnuradio] Separate samples from 2 receive channels

From: Josh Blum
Subject: Re: [Discuss-gnuradio] Separate samples from 2 receive channels
Date: Wed, 07 Nov 2012 09:55:34 -0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121028 Thunderbird/16.0.2

On 11/06/2012 11:15 PM, Dekst wrote:
> Hi, All,
> Can I use one USRP1 and two WBX daughterboards to create 2 concurrent complex 
> receive channels so that I can compare them?
> If I use the rx_multi_samples.cpp example in uhd to receive samples from 2 
> channels (--subdev="A:0 B:0"), and add several lines from 
> rx_samples_to_file.cpp like
>  outfile.write((const char*)&buff.front(), num_rx_samps*sizeof(samp_type));
> to record samples in a file, how can I tell which channel a sample is from?
> Because we have 2 complex receive channels, so the sample order is I_0, Q_0, 
> I_1, Q_1, I_0, Q_0, I_1, Q_1 .... Is this correct?
> If I read the binary file as complex numbers, then odd complex samples are 
> from channel 0 and even complex samples are from channel 1.
> Is my assumption correct?

You might want to look at rx_multi_samples.cpp as an example of a
streamer w/ multiple channels. Basically, the recv() call will fill 2
buffers in this case, not one. In other words, the data is not interleaved.

I also recommend using the gnuradio companion. You can make a simple
flow graph with a USRP source with two output stream and simply connect
2 file sinks.


> Thanks,
> Pei
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> Discuss-gnuradio mailing list
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