Hi,

I have an interesting observation to share, and I want to see if

anybody

can help me shed some light. When I measure time in python in the

following

way:

t1 = datetime.now()

self.start()

t2=datetime.now()

diff = t2.microsecond - t1.microsecond

print “Difference %d”, diff

I get very different time benchmarks…it goes from 309 microseconds

(minimum) to all the way 1 second(max). Do you know why this thread

spawning

is taking such a variety of time after flowgraph start()??

====Code Below=====

#!/usr/bin/env python

from gnuradio import gr, gru, modulation_utils

from gnuradio import usrp

from gnuradio.eng_option import eng_option

from gnuradio import eng_notation

from optparse import OptionParser

from datetime import datetime

import sys

class my_top_block(gr.top_block):

def **init**(self):

gr.top_block.**init**(self)

self.interp = 64

self.waveform_type = gr.GR_GAUSSIAN

self.waveform_ampl = 32000

self.waveform_freq = 2.5e9

self.waveform_offset = 0

self.nsamples = 0

self._instantiate_blocks ()

self.set_waveform_type (self.waveform_type)

```
def usb_freq (self):
return self.u.dac_freq() / self.interp
def usb_throughput (self):
return self.usb_freq () * 4
def set_waveform_type (self, type):
self._configure_graph (type)
self.waveform_type = type
def set_waveform_ampl (self, ampl):
self.waveform_ampl = ampl
self.siggen.set_amplitude (ampl)
self.noisegen.set_amplitude (ampl)
def set_waveform_freq (self, freq):
self.waveform_freq = freq
self.siggen.set_frequency (freq)
def set_waveform_offset (self, offset):
self.waveform_offset = offset
self.siggen.set_offset (offset)
def set_interpolator (self, interp):
self.interp = interp
self.siggen.set_sampling_freq (self.usb_freq ())
self.u.set_interp_rate (interp)
def _instantiate_blocks (self):
self.src = None
self.u = usrp.sink_c (0, self.interp)
self.noisegen = gr.noise_source_c (gr.GR_GAUSSIAN,
self.waveform_ampl)
self.head = None
if self.nsamples > 0:
self.head = gr.head(gr.sizeof_gr_complex,
```

int(self.nsamples))

```
def _configure_graph (self, type):
try:
self.lock()
self.disconnect_all ()
if self.head:
self.connect(self.head, self.u)
tail = self.head
else:
tail = self.u
if type == gr.GR_UNIFORM or type == gr.GR_GAUSSIAN:
self.connect (self.noisegen, tail)
self.noisegen.set_type (type)
self.src = self.noisegen
else:
raise ValueError, type
finally:
self.unlock()
def set_freq(self, target_freq):
r = self.u.tune(self.subdev.which(),self.subdev,2.5e9)
if r:
#print "r.baseband_freq =",
```

eng_notation.num_to_str(r.baseband_freq)

#print “r.dxc_freq =”,

eng_notation.num_to_str(r.dxc_freq)

#print “r.residual_freq =”,

eng_notation.num_to_str(r.residual_freq)

#print “r.inverted =”, r.inverted

return True

```
return False
def build_graph(self):
demods = modulation_utils.type_1_demods()
parser = OptionParser (option_class=eng_option)
parser.add_option ("-T", "--tx-subdev-spec", type="subdev",
```

default=(0, 0),

help=“select USRP Tx side A or B”)

parser.add_option ("-f", “–rf-freq”, type=“eng_float”,

default=None,

help=“set RF center frequency to FREQ”)

parser.add_option ("-i", “–interp”, type=“int”, default=64,

help=“set fgpa interpolation rate to INTERP

[default=%default]”)

parser.add_option ("-d", “–decim”, type=“int”, default=32,

help=“set fgpa decimation rate to DECIM

[default=%default]”)

parser.add_option ("–sine", dest=“type”, action=“store_const”,

const=gr.GR_SIN_WAVE,

help=“generate a complex sinusoid [default]”,

default=gr.GR_SIN_WAVE)

parser.add_option ("–const", dest=“type”, action=“store_const”,

const=gr.GR_CONST_WAVE,

help=“generate a constant output”)

parser.add_option ("–gaussian", dest=“type”,

action=“store_const”,

const=gr.GR_GAUSSIAN,

help=“generate Gaussian random output”)

parser.add_option ("–uniform", dest=“type”, action=“store_const”,

const=gr.GR_UNIFORM,

help=“generate Uniform random output”)

```
parser.add_option ("-w", "--waveform-freq", type="eng_float",
```

default=0,

help=“set waveform frequency to FREQ

[default=%default]”)

parser.add_option ("-a", “–amplitude”, type=“eng_float”,

default=16e3,

help=“set waveform amplitude to AMPLITUDE

[default=%default]”, metavar=“AMPL”)

parser.add_option ("-g", “–gain”, type=“eng_float”, default=None,

help=“set output gain to GAIN

[default=%default]”)

parser.add_option ("-o", “–offset”, type=“eng_float”, default=0,

help=“set waveform offset to OFFSET

[default=%default]”)

parser.add_option ("-N", “–nsamples”, type=“eng_float”,

default=0,

help=“set number of samples to transmit

[default=+inf]”)

(options, args) = parser.parse_args ()

```
if len(args) != 0:
parser.print_help()
raise SystemExit
if options.rf_freq is None:
sys.stderr.write("usrp_siggen: must specify RF center
```

frequency

with -f RF_FREQ\n")

parser.print_help()

raise SystemExit

```
if options.tx_subdev_spec is None:
options.tx_subdev_spec = usrp.pick_tx_subdevice(self.u)
m = usrp.determine_tx_mux_value(self.u, options.tx_subdev_spec)
print "mux = %#04x" % (m,)
self.u.set_mux(m)
self.subdev = usrp.selected_subdev(self.u, options.tx_subdev_spec)
print "Using TX d'board %s" % (self.subdev.side_and_name(),)
if options.gain is None:
self.subdev.set_gain(self.subdev.gain_range()[1]) # set max
```

Tx

gain

else:

self.subdev.set_gain(options.gain) # set max Tx gain

```
if not self.set_freq(options.rf_freq):
sys.stderr.write('Failed to set RF frequency\n')
raise SystemExit
self.subdev.set_enable(True) # enable
```

transmitter

- def start_graph(self):

t1 = datetime.now()

self.start()

t2 = datetime.now()

diff = t2.microsecond - t1.microsecond

print “Time it takes to start the flowgraph%d” % diff*

```
def stop_graph(self):
self.subdev.set_enable(False)
self.stop()
```