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

From: Dekst
Subject: Re: [Discuss-gnuradio] Separate samples from 2 receive channels (Josh Blum)
Date: Fri, 9 Nov 2012 07:13:34 +0800 (CST)

Hi, Josh,

Thanks a lot! Yes, after reading the rx_multi_samples.cpp, I understand that each channel has a buffer and they are placed in a vector buff_ptrs.
For people who may want to use this example in the future, you need to add codes for setting frequency, gain, and antenna. Current example only sets sampling rate for ALL channels. If you want to tune the channel to a certain frequency, you need set_rx_freq(freq, chan) for EACH channel; otherwise you cannot receive what you want as I was stumped.


Message: 2
Date: Wed, 07 Nov 2012 09:55:34 -0800
From: Josh Blum <address@hidden>
To: address@hidden
Subject: Re: [Discuss-gnuradio] Separate samples from 2 receive
Message-ID: <address@hidden>
Content-Type: text/plain; charset=ISO-8859-1

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
> _______________________________________________
> Discuss-gnuradio mailing list
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> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio


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