Re: [Discuss-gnuradio] Asking info about the Interleaving of samples

[Eric Blossom]

On Thu, Mar 29, 2007 at 03:46:12PM +0100, eenrti wrote:
> Hello,
> I have used a sinusoidal signal generator to test my USRP output stream 
> using a single or even the teo inputs to the RX daughterboard.
> I suppose there are 4 channels at the end when I use both RX 
> daughterboard inputs, for I and Q so I tried to separate my output data 
> by using a 4 sample interleaving but it does not seem I can reconstruct 
> my input sinusoidal signal at all.
> 
> I have really a difficult time to decode the output data stream, I know 
> there is some kind of interleaving process, but I cannot speculate what 
> that is, can you please let me know of a reference or of a webpage or if 
> someone can tell me how to separate my output data for each channel?
> 
> Thank you
> 
> Rigas

Hi Rigas, 

I'm having a little bit of a problem understanding your question.

I think that you are using an external signal generator of some kind,
and then are trying to receive and process the signal using the USRP.

What daughterboard are you using?

Assuming that you are using a single Rx daughterboard, and that you
have connected a single output from your signal generator to that
daugtherboard, you can use the usrp_rx_cfile.py command to capture the
data and write it to a file.  The file will contain binary
complex<floats>.  That is, there will be an 32-bit float I, 32-bit
float Q, 32-bit float I, 32-bit float Q...

address@hidden usrp]$ ./usrp_rx_cfile.py --help
usage: usrp_rx_cfile.py: [options] output_filename

options:
  -h, --help            show this help message and exit
  -R RX_SUBDEV_SPEC, --rx-subdev-spec=RX_SUBDEV_SPEC
                        select USRP Rx side A or B (default=A)
  -d DECIM, --decim=DECIM
                        set fgpa decimation rate to DECIM [default=16]
  -f FREQ, --freq=FREQ  set frequency to FREQ
  -g GAIN, --gain=GAIN  set gain in dB (default is midpoint)
  -8, --width-8         Enable 8-bit samples across USB
  --no-hb               don't use halfband filter in usrp
  -s, --output-shorts   output interleaved shorts in stead of complex floats
  -N NSAMPLES, --nsamples=NSAMPLES
                        number of samples to collect [default=+inf]

For example,

address@hidden usrp]$ ./usrp_rx_cfile.py -R a -d 16 -f 2.41G -N 1M  complex.dat

Be sure to to specify a frequency with -f that matches the
capabilities of the daughterboard.  The signal at that center
frequency will end up at DC in the complex baseband output.

You can import the resulting data into octave or matlab by using the
read_complex_binary.m m-file in gnuradio-core/src/utils

Eric