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#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Copyright 2014 Piotr Krysik <ptrkrysik@gmail.com>
#
# 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):
gr.basic_block.__init__(self,
name="gsm_clock_offset_control",
in_sig=[],
out_sig=[])
self.fc = fc
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_estimate = -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_estimate-self.ppm_estimate) > 0.1:
msg_ppm = pmt.from_double(ppm)
self.message_port_pub(pmt.intern("ppm"), msg_ppm)
self.last_ppm_estimate = 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
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