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#!/usr/bin/env python
import random
from gnuradio import gr, gru, usrp
default_access_code = '\xAC\xDD\xA4\xE2\xF2\x8C\x20\xFC'
def string_to_1_0_list(s):
r = []
for ch in s:
x = ord(ch)
for i in range(8):
t = (x >> i) & 0x1
r.append(t)
return r
def to_1_0_string(L):
return ''.join(map(lambda x: chr(x + ord('0')), L))
code = string_to_1_0_list(default_access_code)
access_code = to_1_0_string(code)
def main():
fg = gr.flow_graph()
f_rf = 5e6
fs = 400e3
sr = 100e3
alpha = 0.5
M = 4
k = int(gru.log2(M))
# Source
src = usrp.source_c ()
adc_rate = src.adc_rate()
usrp_decim = int(adc_rate / fs)
src.set_decim_rate(usrp_decim)
subdev_spec = usrp.pick_rx_subdevice(src)
subdev = usrp.selected_subdev(src, subdev_spec)
print "Using RX d'board %s" % (subdev.side_and_name(),)
src.set_mux(usrp.determine_rx_mux_value(src, subdev_spec))
src.tune(0, subdev, f_rf)
g = subdev.gain_range()
subdev.set_gain(g[1])
subdev.set_auto_tr(True)
print "USRP Decimation Rate = %d" % usrp_decim
print "RF Frequency = %d" % f_rf
agc = gr.multiply_const_cc(0.0025)
# Downconverter
costas_alpha=0.005
beta = costas_alpha*costas_alpha*0.25
sync_loop = gr.costas_loop_cc(costas_alpha, beta, 0.05, -0.05, 0)
# Stage 2
# fs2 = 200e3
# D = int(fs / fs2)
# decimator = gr.keep_one_in_n(gr.sizeof_gr_complex, D)
# print "D = %d\nAfter decimator fs = %f" % (D, fs2)
# Demodulator
taps = gr.firdes.root_raised_cosine(1, fs, sr, alpha, 45)
rrc = gr.fir_filter_ccf(1, taps)
# Sampler
mu = 0.01
omega = 4.3
gain_mu = 0.05
gain_omega = 0.25*gain_mu*gain_mu
omega_rel_limit = 0.5
clock_sync = gr.clock_recovery_mm_cc(omega, gain_omega, mu,
gain_mu, omega_rel_limit)
clock_sync.set_verbose(False)
diff_phasor = gr.diff_phasor_cc()
threshold = 12
constellation = (1+0j, 0+1j, -1+0j, 0-1j)
slicer = gr.constellation_decoder_cb((constellation), (0,1,2,3))
unpack = gr.unpack_k_bits_bb(k)
access = gr.correlate_access_code_bb(access_code,threshold)
test = gr.file_sink(gr.sizeof_gr_complex, 'test.dat')
sink = gr.file_sink(gr.sizeof_char, 'output.dat')
fg.connect(src, agc, sync_loop, rrc, clock_sync)
fg.connect(clock_sync, diff_phasor, slicer, unpack, access, sink)
fg.connect(slicer, gr.file_sink(gr.sizeof_char, 'chunks.dat'))
fg.connect(unpack, gr.file_sink(gr.sizeof_char, 'unpack.dat'))
fg.connect(clock_sync, gr.file_sink(gr.sizeof_gr_complex, 'phasor.dat'))
fg.start()
fg.wait()
if __name__ == "__main__":
main()
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