Re: [Discuss-gnuradio] Wideband Spectrum Analyzer

[Santix]

Hi everybody!

I have modified usrp_spectrum_sense.py to plot the results with gnuplot.
There are two files: widespectrum.py and plot.p
I would like everybody to test it and report me the errors and how can I
improve it.
I've used USRPv1 + Flex2400.

Thanks in advance!

Here it goes...

WIDESPECTRUM.PY:

#!/usr/bin/env python
#
# Copyright 2005,2007 Free Software Foundation, Inc.
#
# This file is part of GNU Radio
#
# GNU Radio is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3, or (at your option)
# any later version.
#
# GNU Radio is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with GNU Radio; see the file COPYING.  If not, write to
# the Free Software Foundation, Inc., 51 Franklin Street,
# Boston, MA 02110-1301, USA.
#

from gnuradio import gr, gru, eng_notation, optfir, window
from gnuradio import audio
from gnuradio import usrp
from gnuradio.eng_option import eng_option
from optparse import OptionParser
from usrpm import usrp_dbid
import sys
import math
import struct
import Gnuplot, Gnuplot.funcutils # Added to view the results

class tune(gr.feval_dd):
    """
    This class allows C++ code to callback into python.
    """
    def __init__(self, tb):
        gr.feval_dd.__init__(self)
        self.tb = tb

    def eval(self, ignore):
        """
        This method is called from gr.bin_statistics_f when it wants to
change
        the center frequency.  This method tunes the front end to the new
center
        frequency, and returns the new frequency as its result.
        """
        try:
            # We use this try block so that if something goes wrong from
here
            # down, at least we'll have a prayer of knowing what went wrong.
            # Without this, you get a very mysterious:
            #
            #   terminate called after throwing an instance of
'Swig::DirectorMethodException'
            #   Aborted
            #
            # message on stderr.  Not exactly helpful ;)

            new_freq = self.tb.set_next_freq()
            return new_freq

        except Exception, e:
            print "tune: Exception: ", e


class parse_msg(object):
    def __init__(self, msg):
        self.center_freq = msg.arg1()
        self.vlen = int(msg.arg2())
        assert(msg.length() == self.vlen * gr.sizeof_float)

        # FIXME consider using Numarray or NumPy vector
        t = msg.to_string()
        self.raw_data = t
        self.data = struct.unpack('%df' % (self.vlen,), t)


class my_top_block(gr.top_block):

    def __init__(self):
        gr.top_block.__init__(self)

        usage = "usage: %prog [options] min_freq max_freq"
    # Example:  ./widespectrum.py 2.23G 2.93G
    # that is the maximun range of the USRP Flex2400 device.
       
    parser = OptionParser(option_class=eng_option, usage=usage)
        parser.add_option("-R", "--rx-subdev-spec", type="subdev",
default=(0,0),
                          help="select USRP Rx side A or B (default=A)")
        parser.add_option("-g", "--gain", type="eng_float", default=None,
                          help="set gain in dB (default is midpoint)")
        parser.add_option("", "--tune-delay", type="eng_float",
default=1e-3, metavar="SECS",
                          help="time to delay (in seconds) after changing
frequency [default=%default]")
        parser.add_option("", "--dwell-delay", type="eng_float",
default=10e-3, metavar="SECS",
                          help="time to dwell (in seconds) at a given
frequncy [default=%default]")
        parser.add_option("-F", "--fft-size", type="int", default=256,
                          help="specify number of FFT bins
[default=%default]")
        parser.add_option("-d", "--decim", type="intx", default=64,
                          help="set decimation to DECIM [default=%default]")
        parser.add_option("", "--real-time", action="store_true",
default=False,
                          help="Attempt to enable real-time scheduling")
        parser.add_option("-B", "--fusb-block-size", type="int", default=0,
                          help="specify fast usb block size
[default=%default]")
        parser.add_option("-N", "--fusb-nblocks", type="int", default=0,
                          help="specify number of fast usb blocks
[default=%default]")

        (options, args) = parser.parse_args()
        if len(args) != 2:
            parser.print_help()
            sys.exit(1)

        self.min_freq = eng_notation.str_to_num(args[0])
        self.max_freq = eng_notation.str_to_num(args[1])

        if self.min_freq > self.max_freq:
            self.min_freq, self.max_freq = self.max_freq, self.min_freq   #
swap them
   
    # FIXME We set MANUALLY the physical limits of the device. In this case
the USRP Flex2400 limits.

    if self.min_freq < 2222000000:
        print ("The minimum frequency of this device is 2.222GHz")       
        self.min_freq = 2222000000
   
    if self.max_freq <  2222000000:
        print ("The minimum frequency of this device is 2.222GHz")       
        self.max_freq = 2222000000

    if self.min_freq > 2937000000:
        print ("The maximun frequency of this device is 2.937GHz")
        self.min_freq = 2937000000
   
    if self.max_freq > 2937000000:
        print ("The maximun frequency of this device is 2.937GHz")
        self.max_freq = 2937000000

    if self.min_freq == self.max_freq:
        print ("Do not use this program for a single frecuency analysis
please")
        exit()


    self.fft_size = options.fft_size


        if not options.real_time:
            realtime = False
        else:
            # Attempt to enable realtime scheduling
            r = gr.enable_realtime_scheduling()
            if r == gr.RT_OK:
                realtime = True
            else:
                realtime = False
                print "Note: failed to enable realtime scheduling"

        # If the user hasn't set the fusb_* parameters on the command line,
        # pick some values that will reduce latency.

        if 1:
            if options.fusb_block_size == 0 and options.fusb_nblocks == 0:
                if realtime:                        # be more aggressive
                    options.fusb_block_size = gr.prefs().get_long('fusb',
'rt_block_size', 1024)
                    options.fusb_nblocks    = gr.prefs().get_long('fusb',
'rt_nblocks', 16)
                else:
                    options.fusb_block_size = gr.prefs().get_long('fusb',
'block_size', 4096)
                    options.fusb_nblocks    = gr.prefs().get_long('fusb',
'nblocks', 16)
   
        #print "fusb_block_size =", options.fusb_block_size
    #print "fusb_nblocks    =", options.fusb_nblocks

        # build graph
       
        self.u = usrp.source_c(fusb_block_size=options.fusb_block_size,
                               fusb_nblocks=options.fusb_nblocks)


        adc_rate = self.u.adc_rate()                # 64 MS/s
        usrp_decim = options.decim
        self.u.set_decim_rate(usrp_decim)
        usrp_rate = adc_rate / usrp_decim

        self.u.set_mux(usrp.determine_rx_mux_value(self.u,
options.rx_subdev_spec))
        self.subdev = usrp.selected_subdev(self.u, options.rx_subdev_spec)
        print "Using RX d'board %s" % (self.subdev.side_and_name(),)


    s2v = gr.stream_to_vector(gr.sizeof_gr_complex, self.fft_size)

        mywindow = window.blackmanharris(self.fft_size)
        fft = gr.fft_vcc(self.fft_size, True, mywindow)
        power = 0
        for tap in mywindow:
            power += tap*tap
           
        c2mag = gr.complex_to_mag_squared(self.fft_size)

        # FIXME the log10 primitive is dog slow
        log = gr.nlog10_ff(10, self.fft_size,
                          
-20*math.log10(self.fft_size)-10*math.log10(power/self.fft_size))
       
        # Set the freq_step to 75% of the actual data throughput.
        # This allows us to discard the bins on both ends of the spectrum.
   
   

    self.freq_step = 0.75 * usrp_rate
        self.min_center_freq = self.min_freq + self.freq_step/2
        nsteps = math.ceil((self.max_freq - self.min_freq) / self.freq_step)
        self.max_center_freq = self.min_center_freq + (nsteps *
self.freq_step)

        self.next_freq = self.min_center_freq

    # We define the minimum, maximum and frequency step in a global
statement to use them later.

    global min_center_freq, max_center_freq, freq_step       
    min_center_freq = self.min_center_freq
    max_center_freq = self.max_center_freq
    freq_step = self.freq_step
   
   
        tune_delay  = max(0, int(round(options.tune_delay * usrp_rate /
self.fft_size)))  # in fft_frames
        dwell_delay = max(1, int(round(options.dwell_delay * usrp_rate /
self.fft_size))) # in fft_frames

        self.msgq = gr.msg_queue(16)
        self._tune_callback = tune(self)        # hang on to this to keep it
from being GC'd
        stats = gr.bin_statistics_f(self.fft_size, self.msgq,
                                    self._tune_callback, tune_delay,
dwell_delay)

        # FIXME leave out the log10 until we speed it up
    self.connect(self.u, s2v, fft, c2mag, log, stats)
    #self.connect(self.u, s2v, fft, c2mag, stats)

        if options.gain is None:
            # if no gain was specified, use the mid-point in dB
            g = self.subdev.gain_range()
            options.gain = float(g[0]+g[1])/2

        self.set_gain(options.gain)
    print "gain =", options.gain


    def set_next_freq(self):
        target_freq = self.next_freq
        self.next_freq = self.next_freq + self.freq_step
        if self.next_freq >= self.max_center_freq:
            self.next_freq = self.min_center_freq
   
        if not self.set_freq(target_freq):
            print "Failed to set frequency to", target_freq

        return target_freq
                         

    def set_freq(self, target_freq):
        """
        Set the center frequency we're interested in.

        @param target_freq: frequency in Hz
        @rypte: bool

        Tuning is a two step process.  First we ask the front-end to
        tune as close to the desired frequency as it can.  Then we use
        the result of that operation and our target_frequency to
        determine the value for the digital down converter.
        """
        return self.u.tune(0, self.subdev, target_freq)


    def set_gain(self, gain):
        self.subdev.set_gain(gain)

def mean(data):                # Returns the arithmetic mean of a numeric
list
   return sum(data) / len(data)


def main_loop(tb):
   
    # We give basic information about the Spectrum Analysis

    print "The start frequency is %s Hz" % min_center_freq
    print "The final frequency is %s Hz" % max_center_freq
    print "The frequency step is %s Hz" % freq_step
    g = Gnuplot.Gnuplot(debug=1)
   
    while 1:

        # Get the next message sent from the C++ code (blocking call).
        # It contains the center frequency and the mag squared of the fft
        m = parse_msg(tb.msgq.delete_head())

        # Print center freq so we know that something is happening...
        #print (m.center_freq)
   
    # FIXME do something useful with the data...


    # Mechanism to save in a file (power.dat) 2 columns, one for the
frequencies and the other for the mean of the FFT_SIZE points of m.data
   
    if m.center_freq == min_center_freq:    # If we get the minimum
frequency, it'll reset the power.dat file
        power=open("power.dat", "w")    # It will overwrite the power.dat
file
   
    power=open("power.dat", "a")        # Each loop, it adds a dataline
(append)
    p=str(m.center_freq)            # with a frequency and the mean of the
256 FFT samples (Power in dB)
    media=str(mean(m.data))            #
    todo= p + "    " + media + '\n'        #
    power.write(todo)            #
   
   
    if m.center_freq == (max_center_freq-freq_step):    # If it gets the
final frecuency
                               
        p=str(m.center_freq)                # It'll write the last frecuency
with its Power in the power.dat file
        media=str(mean(m.data))                #
        todo= p + "    " + media + '\n'            #
        power.write(todo)                #      
        g.load("plot.p")                # Load the plot with the data
obtained from URSP
        power=open("power.dat", "a")            # Without this line, the
file will start with the last frecuency
        #g.hardcopy('spectrum.ps', enhanced=1, color=1)        # It does a
plot copy to the hard disk (I think there's not enough time to do it)
                    

    # m.data in 'w' mode: only write, if it exist a file with the same name,
it'll be overwrite.
    #           'a' to append
    #        'r+' for read and write

        # m.data are the mag_squared of the fft output (they are in the
        # standard order.  I.e., bin 0 == DC.)
        # You'll probably want to do the equivalent of "fftshift" on them
   
    # m.raw_data is a string that contains the binary floats.
        # You could write this as binary to a file.

   
if __name__ == '__main__':
    tb = my_top_block()
    try:
        tb.start()              # start executing flow graph in another
thread...
        main_loop(tb)
           
    except KeyboardInterrupt:
        pass


PLOT.P

set autoscale
unset logscale
unset label
set xtic auto
set ytic auto
set title "Wideband Spectrum Analyzer"
set xlabel "Frecuency"
set ylabel "Power (dB)"
set grid
plot "power.dat" using 1:2 title 'Mean power' with linespoints
-- 
View this message in context: 
http://www.nabble.com/Wideband-Spectrum-Analyzer-tp19974701p20343196.html
Sent from the GnuRadio mailing list archive at Nabble.com.