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#!/usr/bin/env python
# $Id: gssm_usrp.py,v 1.2 2007-07-07 16:31:44 jl Exp $
from gnuradio import gr, usrp, db_dbs_rx, blks2
from gnuradio.blks2impl import gmsk
from usrpm import usrp_dbid
import gssm
import sys
# constant
gsm_rate = 1625000.0 / 6.0
# script constant
decim = 112
gain = 70
# bts channel
c0 = 875.4e6
# experimental constant
default_usrp_offset = 12e3
class gssm_flow_graph(gr.top_block):
def __init__(self, usrp_offset):
gr.top_block.__init__(self)
u = usrp.source_c(decim_rate = decim)
s = usrp.pick_subdev(u, (usrp_dbid.DBS_RX,))
u.set_mux(usrp.determine_rx_mux_value(u, s))
subdev = usrp.selected_subdev(u, s)
if subdev.dbid() != usrp_dbid.DBS_RX:
raise Exception('dbs daughterboard not detected!')
subdev.set_gain(gain)
sps = u.adc_freq() / u.decim_rate()
if sps < 2 * gsm_rate:
raise Exception('sample rate too low')
u.tune(0, subdev, c0 + usrp_offset)
xcf = 150e3
xtw = 50e3
xt = gr.firdes.low_pass(1.0, sps, xcf, xtw,
gr.firdes.WIN_HAMMING)
xf = gr.fir_filter_ccf(1, xt)
g = gssm.sink(sps)
self.connect(u, xf, g)
def main():
if len(sys.argv) == 2:
uo = float(sys.argv[1])
else:
uo = default_usrp_offset
g = gssm_flow_graph(uo)
g.run()
if __name__ == '__main__':
main()
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