[Discuss-gnuradio] question using signals in flowgraphs

[Steve Mcmahon]

Hello:

I have a USRP2 + WBX running with GNU Radio 3.3.0 on openSUSE 11.2.

I created a simple flowgraph using GRC, a Signal Source connected into a USRP2 
Sink, used to generate a tone. I'm trying to setup a timer in the flowgraph so 
that every 2 seconds, the tone flip-flops between 3 kHz and 6 kHz. When I run 
it, I get a tone at 1 kHz that never changes (the default tone freq from the 
parameter list). It seems that my signal handler is never getting called. I 
copied my code below. Could anyone tell me why is my signal handler never 
getting called? What am I doing wrong here? 

Thanks for your help.



#!/usr/bin/env python
##################################################
# Gnuradio Python Flow Graph
# Title: Tst Generate Tone
# Generated: Mon Dec  6 01:19:50 2010
##################################################

from gnuradio import eng_notation
from gnuradio import gr
from gnuradio import usrp2
from gnuradio.eng_option import eng_option
from gnuradio.gr import firdes
from grc_gnuradio import wxgui as grc_wxgui
from optparse import OptionParser
import wx

import signal
import time
import datetime
timer_tick_cnt = 0
timer_interval = 2.0

class tst_generate_tone(grc_wxgui.top_block_gui):

        def __init__(self, p_eth="eth1", p_freq_carrier=900.0e6, 
p_freq_tone=1.0e3, p_interp=500):
                grc_wxgui.top_block_gui.__init__(self, title="Tst Generate 
Tone")

                ##################################################
                # Parameters
                ##################################################
                self.p_eth = p_eth
                self.p_freq_carrier = p_freq_carrier
                self.p_freq_tone = p_freq_tone
                self.p_interp = p_interp

                ##################################################
                # Variables
                ##################################################
                self.samp_rate = samp_rate = 100000000/p_interp

                ##################################################
                # Blocks
                ##################################################
                self.gr_sig_source_x_0 = gr.sig_source_c(samp_rate, 
gr.GR_COS_WAVE, p_freq_tone, 0.4, 0)
                self.usrp2_sink_xxxx_0 = usrp2.sink_32fc(p_eth)
                self.usrp2_sink_xxxx_0.set_interp(p_interp)
                self.usrp2_sink_xxxx_0.set_center_freq(p_freq_carrier)
                self.usrp2_sink_xxxx_0.set_gain(0)
                self.usrp2_sink_xxxx_0.config_mimo(usrp2.MC_WE_LOCK_TO_SMA)

                ##################################################
                # Connections
                ##################################################
                self.connect((self.gr_sig_source_x_0, 0), 
(self.usrp2_sink_xxxx_0, 0))

        def set_p_eth(self, p_eth):
                self.p_eth = p_eth

        def set_p_freq_carrier(self, p_freq_carrier):
                self.p_freq_carrier = p_freq_carrier
                self.usrp2_sink_xxxx_0.set_center_freq(self.p_freq_carrier)

        def set_p_freq_tone(self, p_freq_tone):
                self.p_freq_tone = p_freq_tone
                self.gr_sig_source_x_0.set_frequency(self.p_freq_tone)

        def set_p_interp(self, p_interp):
                self.p_interp = p_interp
                self.set_samp_rate(100000000/self.p_interp)
                self.usrp2_sink_xxxx_0.set_interp(self.p_interp)

        def set_samp_rate(self, samp_rate):
                self.samp_rate = samp_rate
                self.gr_sig_source_x_0.set_sampling_freq(self.samp_rate)

def alarm_handler(signo, frame):
        global timer_tick_cnt
        print "timer tick count is ", timer_tick_cnt
        timer_tick_cnt = timer_tick_cnt + 1
        new_freq = ((timer_tick_cnt % 2) + 1) * 3000.0
        tst_generate_tone.gr_sig_source_x_0.set_ffrequency(new_freq)

if __name__ == '__main__':
        parser = OptionParser(option_class=eng_option, usage="%prog: [options]")
        parser.add_option("", "--p-eth", dest="p_eth", type="string", 
default="eth1",
                help="Set p_eth [default=%default]")
        parser.add_option("", "--p-freq-carrier", dest="p_freq_carrier", 
type="eng_float", default=eng_notation.num_to_str(900.0e6),
                help="Set p_freq_carrier [default=%default]")
        parser.add_option("", "--p-freq-tone", dest="p_freq_tone", 
type="eng_float", default=eng_notation.num_to_str(1.0e3),
                help="Set p_freq_tone [default=%default]")
        parser.add_option("", "--p-interp", dest="p_interp", type="intx", 
default=500,
                help="Set p_interp [default=%default]")
        (options, args) = parser.parse_args()
        if gr.enable_realtime_scheduling() != gr.RT_OK:
                print "Error: failed to enable realtime scheduling."

        signal.signal(signal.SIGALRM, alarm_handler)
        signal.setitimer(signal.ITIMER_REAL, timer_interval, timer_interval)

        tb = tst_generate_tone(p_eth=options.p_eth, 
p_freq_carrier=options.p_freq_carrier, p_freq_tone=options.p_freq_tone, 
p_interp=options.p_interp)
        tb.Run(True)