# Separate samples from 2 receive channels **URL:** \ **Category:** GNU Radio\ **Created:** [November 7, 2012, 8:16am UTC](https://www.ruby-forum.com/t/separate-samples-from-2-receive-channels/224298 "2012-11-07T08:16:38Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![aris](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/258eb7/32.png) [@aris](https://www.ruby-forum.com/u/aris)\ **Post date:** [November 7, 2012, 8:16am UTC](https://www.ruby-forum.com/t/separate-samples-from-2-receive-channels/224298/1 "2012-11-07T08:16:38Z")
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? Thanks, Pei ---
**Author:** ![casper\_the\_ghost](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/58956e/32.png) [@casper\_the\_ghost](https://www.ruby-forum.com/u/casper_the_ghost)\ **Post date:** [November 7, 2012, 6:56pm UTC](https://www.ruby-forum.com/t/separate-samples-from-2-receive-channels/224298/2 "2012-11-07T18:56:25Z")
On 11/06/2012 11:15 PM, Dekst wrote: > 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. -josh