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Diffstat (limited to 'python/receiver/clock_offset_control.py')
| -rw-r--r-- | python/receiver/clock_offset_control.py | 102 |
1 files changed, 102 insertions, 0 deletions
diff --git a/python/receiver/clock_offset_control.py b/python/receiver/clock_offset_control.py new file mode 100644 index 0000000..506b0fd --- /dev/null +++ b/python/receiver/clock_offset_control.py @@ -0,0 +1,102 @@ +#!/usr/bin/env python +# -*- coding: utf-8 -*- +# +# Copyright 2014 <+YOU OR YOUR COMPANY+>. +# +# This is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 3, or (at your option) +# any later version. +# +# This software is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this software; see the file COPYING. If not, write to +# the Free Software Foundation, Inc., 51 Franklin Street, +# Boston, MA 02110-1301, USA. +# + +from numpy import * +from gnuradio import gr +import pmt +from threading import Timer + +class clock_offset_control(gr.basic_block): + """ + docstring for block clock_offset_control + """ + def __init__(self, fc, samp_rate): + gr.basic_block.__init__(self, + name="gsm_clock_offset_control", + in_sig=[], + out_sig=[]) + self.fc = fc + self.samp_rate = samp_rate + self.message_port_register_in(pmt.intern("measurements")) + self.set_msg_handler(pmt.intern("measurements"), self.process_measurement) + self.message_port_register_out(pmt.intern("ppm")) + self.alfa = 0.3 + self.ppm_estimate = -1e6 + self.first_measurement = True + self.counter = 0 + self.last_state = "" + self.timer = Timer(0.5, self.timed_reset) + self.last_ppm = -1e6 + + def process_measurement(self,msg): + if pmt.is_tuple(msg): + key = pmt.symbol_to_string(pmt.tuple_ref(msg,0)) + if key == "freq_offset": + freq_offset = pmt.to_double(pmt.tuple_ref(msg,1)) + ppm = -freq_offset/self.fc*1.0e6 + state = pmt.symbol_to_string(pmt.tuple_ref(msg,2)) + + self.last_state = state + + if abs(ppm) > 100: #safeguard against flawed measurements + ppm = 0 + self.reset() + + if state == "fcch_search": + msg_ppm = pmt.from_double(ppm) + self.message_port_pub(pmt.intern("ppm"), msg_ppm) + self.timer.cancel() + self.timer = Timer(0.5, self.timed_reset) + self.timer.start() + elif state == "synchronized": + self.timer.cancel() + if self.first_measurement: + self.ppm_estimate = ppm + self.first_measurement = False + else: + self.ppm_estimate = (1-self.alfa)*self.ppm_estimate+self.alfa*ppm + + if self.counter == 5: + self.counter = 0 + if abs(self.last_ppm-self.ppm_estimate) > 0.1: + msg_ppm = pmt.from_double(ppm) + self.message_port_pub(pmt.intern("ppm"), msg_ppm) + self.last_ppm = self.ppm_estimate + else: + self.counter=self.counter+1 + elif state == "sync_loss": + self.reset() + msg_ppm = pmt.from_double(0.0) + self.message_port_pub(pmt.intern("ppm"), msg_ppm) + + + def timed_reset(self): + if self.last_state != "synchronized": +# print "conditional reset" + self.reset() + msg_ppm = pmt.from_double(0.0) + self.message_port_pub(pmt.intern("ppm"), msg_ppm) + + def reset(self): + self.ppm_estimate = -1e6 + self.counter = 0 + self.first_measurement = True + |