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