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#!/usr/bin/env python
from gnuradio import gr, gru, usrp, optfir, eng_notation, blks, pager
from gnuradio.eng_option import eng_option
from optparse import OptionParser
import time, os, sys
from string import split, join
"""
This example application demonstrates receiving and demodulating the
FLEX pager protocol.
A receive chain is built up of the following signal processing
blocks:
USRP - Daughter board source generating complex baseband signal.
CHAN - Low pass filter to select channel bandwidth
AGC - Automatic gain control leveling signal at [-1.0, +1.0]
FLEX - FLEX pager protocol decoder
The following are required command line parameters:
-f FREQ USRP receive frequency
The following are optional command line parameters:
-R SUBDEV Daughter board specification, defaults to first found
-c FREQ Calibration offset. Gets added to receive frequency.
Defaults to 0.0 Hz.
-g GAIN Daughterboard gain setting. Defaults to mid-range.
-r RFSQL RF squelch in db. Defaults to -50.0.
Once the program is running, ctrl-break (Ctrl-C) stops operation.
"""
class usrp_source_c(gr.hier_block):
"""
Create a USRP source object supplying complex floats.
Selects user supplied subdevice or chooses first available one.
Calibration value is the offset from the tuned frequency to
the actual frequency.
"""
def __init__(self, fg, subdev_spec, decim, gain=None, calibration=0.0):
self._decim = decim
self._src = usrp.source_c()
if subdev_spec is None:
subdev_spec = usrp.pick_rx_subdevice(self._src)
self._subdev = usrp.selected_subdev(self._src, subdev_spec)
self._src.set_mux(usrp.determine_rx_mux_value(self._src, subdev_spec))
self._src.set_decim_rate(self._decim)
# If no gain specified, set to midrange
if gain is None:
g = self._subdev.gain_range()
gain = (g[0]+g[1])/2.0
self._subdev.set_gain(gain)
self._cal = calibration
gr.hier_block.__init__(self, fg, self._src, self._src)
def tune(self, freq):
result = usrp.tune(self._src, 0, self._subdev, freq+self._cal)
# TODO: deal with residual
def rate(self):
return self._src.adc_rate()/self._decim
class app_flow_graph(gr.flow_graph):
def __init__(self, options, args, queue):
gr.flow_graph.__init__(self)
self.options = options
self.args = args
USRP = usrp_source_c(self, # Flow graph
options.rx_subdev_spec, # Daugherboard spec
256, # IF decimation ratio gets 250K if_rate
options.gain, # Receiver gain
options.calibration) # Frequency offset
USRP.tune(options.frequency)
if_rate = USRP.rate()
channel_rate = 25000
channel_decim = int(if_rate / channel_rate)
CHAN_taps = optfir.low_pass(1.0, # Filter gain
if_rate, # Sample rate
8000, # One sided modulation bandwidth
10000, # One sided channel bandwidth
0.1, # Passband ripple
60) # Stopband attenuation
CHAN = gr.freq_xlating_fir_filter_ccf(channel_decim, # Decimation rate
CHAN_taps, # Filter taps
0.0, # Offset frequency
if_rate) # Sample rate
AGC = gr.agc_cc(1.0/channel_rate, # Time constant
1.0, # Reference power
1.0, # Initial gain
1.0) # Maximum gain
FLEX = pager.flex_demod(self, 25000, queue)
self.connect(USRP, CHAN, AGC, FLEX.INPUT)
def main():
parser = OptionParser(option_class=eng_option)
parser.add_option("-f", "--frequency", type="eng_float",
help="set receive frequency to Hz", metavar="Hz")
parser.add_option("-R", "--rx-subdev-spec", type="subdev",
help="select USRP Rx side A or B", metavar="SUBDEV")
parser.add_option("-c", "--calibration", type="eng_float", default=0.0,
help="set frequency offset to Hz", metavar="Hz")
parser.add_option("-g", "--gain", type="int", default=None,
help="set RF gain", metavar="dB")
(options, args) = parser.parse_args()
if options.frequency < 1e6:
options.frequency *= 1e6
queue = gr.msg_queue()
fg = app_flow_graph(options, args, queue)
try:
fg.start()
while 1:
msg = queue.delete_head() # Blocking read
fields = split(msg.to_string(), chr(128))
print join(fields, '|')
except KeyboardInterrupt:
fg.stop()
if __name__ == "__main__":
main()
|
