mirror of https://github.com/gnss-sdr/gnss-sdr
440 lines
20 KiB
C++
440 lines
20 KiB
C++
/*!
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* \file gps_l1_ca_telemetry_decoder_cc.cc
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* \brief Implementation of a NAV message demodulator block based on
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* Kay Borre book MATLAB-based GPS receiver
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* \author Javier Arribas, 2011. jarribas(at)cttc.es
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*
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* -------------------------------------------------------------------------
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*
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* Copyright (C) 2010-2015 (see AUTHORS file for a list of contributors)
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*
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* GNSS-SDR is a software defined Global Navigation
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* Satellite Systems receiver
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*
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* This file is part of GNSS-SDR.
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*
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* GNSS-SDR 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 of the License, or
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* (at your option) any later version.
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*
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* GNSS-SDR 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 GNSS-SDR. If not, see <http://www.gnu.org/licenses/>.
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*
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* -------------------------------------------------------------------------
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*/
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#include "gps_l1_ca_telemetry_decoder_cc.h"
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#include <iostream>
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#include <boost/lexical_cast.hpp>
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#include <gnuradio/io_signature.h>
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#include <glog/logging.h>
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#include "control_message_factory.h"
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#ifndef _rotl
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#define _rotl(X,N) ((X << N) ^ (X >> (32-N))) // Used in the parity check algorithm
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#endif
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using google::LogMessage;
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gps_l1_ca_telemetry_decoder_cc_sptr
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gps_l1_ca_make_telemetry_decoder_cc(const Gnss_Satellite & satellite, bool dump)
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{
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return gps_l1_ca_telemetry_decoder_cc_sptr(new gps_l1_ca_telemetry_decoder_cc(satellite, dump));
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}
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gps_l1_ca_telemetry_decoder_cc::gps_l1_ca_telemetry_decoder_cc(
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const Gnss_Satellite & satellite,
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bool dump) :
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gr::block("gps_navigation_cc", gr::io_signature::make(1, 1, sizeof(Gnss_Synchro)),
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gr::io_signature::make(1, 1, sizeof(Gnss_Synchro)))
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{
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// Telemetry Bit transition synchronization port out
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this->message_port_register_out(pmt::mp("preamble_timestamp_s"));
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// Ephemeris data port out
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this->message_port_register_out(pmt::mp("telemetry"));
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// initialize internal vars
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d_dump = dump;
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d_satellite = Gnss_Satellite(satellite.get_system(), satellite.get_PRN());
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// set the preamble
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unsigned short int preambles_bits[GPS_CA_PREAMBLE_LENGTH_BITS] = GPS_PREAMBLE;
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//memcpy((unsigned short int*)this->d_preambles_bits, (unsigned short int*)preambles_bits, GPS_CA_PREAMBLE_LENGTH_BITS*sizeof(unsigned short int));
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// preamble bits to sampled symbols
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d_preambles_symbols = static_cast<signed int*>(malloc(sizeof(signed int) * GPS_CA_PREAMBLE_LENGTH_SYMBOLS));
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int n = 0;
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for (int i = 0; i < GPS_CA_PREAMBLE_LENGTH_BITS; i++)
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{
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for (unsigned int j = 0; j < GPS_CA_TELEMETRY_SYMBOLS_PER_BIT; j++)
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{
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if (preambles_bits[i] == 1)
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{
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d_preambles_symbols[n] = 1;
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}
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else
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{
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d_preambles_symbols[n] = -1;
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}
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n++;
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}
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}
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d_stat = 0;
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d_symbol_accumulator = 0;
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d_symbol_accumulator_counter = 0;
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d_frame_bit_index = 0;
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d_flag_frame_sync = false;
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d_GPS_frame_4bytes = 0;
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d_prev_GPS_frame_4bytes = 0;
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d_flag_parity = false;
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d_TOW_at_Preamble = 0;
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d_TOW_at_current_symbol = 0;
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flag_TOW_set = false;
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d_average_count = 0;
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d_flag_preamble = false;
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d_flag_new_tow_available = false;
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d_word_number = 0;
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d_decimation_output_factor = 1;
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d_channel = 0;
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flag_PLL_180_deg_phase_locked = false;
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d_preamble_time_samples = 0;
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}
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gps_l1_ca_telemetry_decoder_cc::~gps_l1_ca_telemetry_decoder_cc()
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{
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delete d_preambles_symbols;
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if(d_dump_file.is_open() == true)
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{
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try
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{
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d_dump_file.close();
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}
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catch(const std::exception & ex)
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{
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LOG(WARNING) << "Exception in destructor closing the dump file " << ex.what();
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}
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}
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}
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bool gps_l1_ca_telemetry_decoder_cc::gps_word_parityCheck(unsigned int gpsword)
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{
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unsigned int d1, d2, d3, d4, d5, d6, d7, t, parity;
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/* XOR as many bits in parallel as possible. The magic constants pick
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up bits which are to be XOR'ed together to implement the GPS parity
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check algorithm described in IS-GPS-200E. This avoids lengthy shift-
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and-xor loops. */
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d1 = gpsword & 0xFBFFBF00;
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d2 = _rotl(gpsword,1) & 0x07FFBF01;
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d3 = _rotl(gpsword,2) & 0xFC0F8100;
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d4 = _rotl(gpsword,3) & 0xF81FFE02;
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d5 = _rotl(gpsword,4) & 0xFC00000E;
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d6 = _rotl(gpsword,5) & 0x07F00001;
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d7 = _rotl(gpsword,6) & 0x00003000;
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t = d1 ^ d2 ^ d3 ^ d4 ^ d5 ^ d6 ^ d7;
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// Now XOR the 5 6-bit fields together to produce the 6-bit final result.
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parity = t ^ _rotl(t,6) ^ _rotl(t,12) ^ _rotl(t,18) ^ _rotl(t,24);
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parity = parity & 0x3F;
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if (parity == (gpsword & 0x3F)) return(true);
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else return(false);
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}
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int gps_l1_ca_telemetry_decoder_cc::general_work (int noutput_items __attribute__((unused)), gr_vector_int &ninput_items __attribute__((unused)),
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gr_vector_const_void_star &input_items, gr_vector_void_star &output_items)
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{
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int corr_value = 0;
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int preamble_diff_ms = 0;
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Gnss_Synchro **out = reinterpret_cast<Gnss_Synchro **>(&output_items[0]); // Get the output buffer pointer
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const Gnss_Synchro **in = reinterpret_cast<const Gnss_Synchro **>(&input_items[0]); // Get the input buffer pointer
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Gnss_Synchro current_symbol; //structure to save the synchronization information and send the output object to the next block
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//1. Copy the current tracking output
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current_symbol = in[0][0];
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d_symbol_history.push_back(current_symbol); //add new symbol to the symbol queue
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consume_each(1);
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unsigned int required_symbols = GPS_CA_PREAMBLE_LENGTH_SYMBOLS;
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d_flag_preamble = false;
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if (d_symbol_history.size()>required_symbols)
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{
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//******* preamble correlation ********
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for (unsigned int i = 0; i < GPS_CA_PREAMBLE_LENGTH_SYMBOLS; i++)
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{
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if (d_symbol_history.at(i).Flag_valid_symbol_output == true)
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{
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if (d_symbol_history.at(i).Prompt_I < 0) // symbols clipping
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{
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corr_value -= d_preambles_symbols[i] * d_symbol_history.at(i).correlation_length_ms;
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}
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else
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{
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corr_value += d_preambles_symbols[i] * d_symbol_history.at(i).correlation_length_ms;
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}
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}
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if (corr_value >= GPS_CA_PREAMBLE_LENGTH_SYMBOLS) break;
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}
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}
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//******* frame sync ******************
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if (abs(corr_value) == GPS_CA_PREAMBLE_LENGTH_SYMBOLS)
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{
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//TODO: Rewrite with state machine
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if (d_stat == 0)
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{
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d_GPS_FSM.Event_gps_word_preamble();
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//record the preamble sample stamp
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d_preamble_time_samples = d_symbol_history.at(0).Tracking_sample_counter; // record the preamble sample stamp
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DLOG(INFO) << "Preamble detection for SAT " << this->d_satellite << "d_symbol_history.at(0).Tracking_sample_counter=" << d_symbol_history.at(0).Tracking_sample_counter;
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//sync the symbol to bits integrator
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d_symbol_accumulator = 0;
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d_symbol_accumulator_counter = 0;
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d_frame_bit_index = 0;
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d_stat = 1; // enter into frame pre-detection status
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}
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else if (d_stat == 1) //check 6 seconds of preamble separation
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{
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preamble_diff_ms = round(((static_cast<double>(d_symbol_history.at(0).Tracking_sample_counter) - d_preamble_time_samples) / static_cast<double>(d_symbol_history.at(0).fs)) * 1000.0);
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if (abs(preamble_diff_ms - GPS_SUBFRAME_MS) < 1)
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{
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DLOG(INFO) << "Preamble confirmation for SAT " << this->d_satellite;
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d_GPS_FSM.Event_gps_word_preamble();
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d_flag_preamble = true;
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d_preamble_time_samples = d_symbol_history.at(0).Tracking_sample_counter; // record the PRN start sample index associated to the preamble
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if (!d_flag_frame_sync)
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{
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// send asynchronous message to tracking to inform of frame sync and extend correlation time
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pmt::pmt_t value = pmt::from_double(static_cast<double>(d_preamble_time_samples) / static_cast<double>(d_symbol_history.at(0).fs) - 0.001);
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this->message_port_pub(pmt::mp("preamble_timestamp_s"), value);
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d_flag_frame_sync = true;
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if (corr_value < 0)
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{
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flag_PLL_180_deg_phase_locked = true; // PLL is locked to opposite phase!
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DLOG(INFO) << " PLL in opposite phase for Sat "<< this->d_satellite.get_PRN();
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}
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else
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{
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flag_PLL_180_deg_phase_locked = false;
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}
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DLOG(INFO) << " Frame sync SAT " << this->d_satellite << " with preamble start at "
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<< static_cast<double>(d_preamble_time_samples) / static_cast<double>(d_symbol_history.at(0).fs) << " [s]";
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}
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}
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}
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}
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else
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{
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if (d_stat == 1)
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{
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preamble_diff_ms = round(((static_cast<double>(d_symbol_history.at(0).Tracking_sample_counter) - static_cast<double>(d_preamble_time_samples)) / static_cast<double>(d_symbol_history.at(0).fs)) * 1000.0);
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if (preamble_diff_ms > GPS_SUBFRAME_MS + 1)
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{
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DLOG(INFO) << "Lost of frame sync SAT " << this->d_satellite << " preamble_diff= " << preamble_diff_ms;
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d_stat = 0; //lost of frame sync
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d_flag_frame_sync = false;
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flag_TOW_set = false;
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}
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}
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}
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//******* SYMBOL TO BIT *******
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if (d_symbol_history.at(0).Flag_valid_symbol_output == true)
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{
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// extended correlation to bit period is enabled in tracking!
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d_symbol_accumulator += d_symbol_history.at(0).Prompt_I; // accumulate the input value in d_symbol_accumulator
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d_symbol_accumulator_counter += d_symbol_history.at(0).correlation_length_ms;
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}
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if (d_symbol_accumulator_counter >= 20)
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{
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if (d_symbol_accumulator > 0)
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{ //symbol to bit
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d_GPS_frame_4bytes += 1; //insert the telemetry bit in LSB
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}
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d_symbol_accumulator = 0;
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d_symbol_accumulator_counter = 0;
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//******* bits to words ******
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d_frame_bit_index++;
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if (d_frame_bit_index == 30)
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{
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d_frame_bit_index = 0;
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// parity check
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// Each word in wordbuff is composed of:
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// Bits 0 to 29 = the GPS data word
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// Bits 30 to 31 = 2 LSBs of the GPS word ahead.
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// prepare the extended frame [-2 -1 0 ... 30]
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if (d_prev_GPS_frame_4bytes & 0x00000001)
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{
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d_GPS_frame_4bytes = d_GPS_frame_4bytes | 0x40000000;
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}
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if (d_prev_GPS_frame_4bytes & 0x00000002)
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{
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d_GPS_frame_4bytes = d_GPS_frame_4bytes | 0x80000000;
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}
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/* Check that the 2 most recently logged words pass parity. Have to first
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invert the data bits according to bit 30 of the previous word. */
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if(d_GPS_frame_4bytes & 0x40000000)
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{
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d_GPS_frame_4bytes ^= 0x3FFFFFC0; // invert the data bits (using XOR)
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}
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if (gps_l1_ca_telemetry_decoder_cc::gps_word_parityCheck(d_GPS_frame_4bytes))
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{
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memcpy(&d_GPS_FSM.d_GPS_frame_4bytes, &d_GPS_frame_4bytes, sizeof(char)*4);
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//d_GPS_FSM.d_preamble_time_ms = d_preamble_time_seconds * 1000.0;
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d_GPS_FSM.Event_gps_word_valid();
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// send TLM data to PVT using asynchronous message queues
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if (d_GPS_FSM.d_flag_new_subframe == true)
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{
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switch (d_GPS_FSM.d_subframe_ID)
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{
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case 3: //we have a new set of ephemeris data for the current SV
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if (d_GPS_FSM.d_nav.satellite_validation() == true)
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{
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// get ephemeris object for this SV (mandatory)
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std::shared_ptr<Gps_Ephemeris> tmp_obj = std::make_shared<Gps_Ephemeris>(d_GPS_FSM.d_nav.get_ephemeris());
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this->message_port_pub(pmt::mp("telemetry"), pmt::make_any(tmp_obj));
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}
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break;
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case 4: // Possible IONOSPHERE and UTC model update (page 18)
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if (d_GPS_FSM.d_nav.flag_iono_valid == true)
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{
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std::shared_ptr<Gps_Iono> tmp_obj = std::make_shared<Gps_Iono>( d_GPS_FSM.d_nav.get_iono());
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this->message_port_pub(pmt::mp("telemetry"), pmt::make_any(tmp_obj));
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}
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if (d_GPS_FSM.d_nav.flag_utc_model_valid == true)
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{
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std::shared_ptr<Gps_Utc_Model> tmp_obj = std::make_shared<Gps_Utc_Model>(d_GPS_FSM.d_nav.get_utc_model());
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this->message_port_pub(pmt::mp("telemetry"), pmt::make_any(tmp_obj));
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}
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break;
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case 5:
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// get almanac (if available)
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//TODO: implement almanac reader in navigation_message
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break;
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default:
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break;
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}
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d_GPS_FSM.clear_flag_new_subframe();
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d_flag_new_tow_available=true;
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}
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d_flag_parity = true;
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}
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else
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{
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d_GPS_FSM.Event_gps_word_invalid();
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d_flag_parity = false;
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}
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d_prev_GPS_frame_4bytes = d_GPS_frame_4bytes; // save the actual frame
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d_GPS_frame_4bytes = d_GPS_frame_4bytes & 0;
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}
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else
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{
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d_GPS_frame_4bytes <<= 1; //shift 1 bit left the telemetry word
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}
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}
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//2. Add the telemetry decoder information
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if (this->d_flag_preamble == true and d_flag_new_tow_available == true)
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{
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//double decoder_latency_ms=(double)(current_symbol.Tracking_sample_counter-d_symbol_history.at(0).Tracking_sample_counter)
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// /(double)current_symbol.fs;
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// update TOW at the preamble instant (account with decoder latency)
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d_TOW_at_Preamble = d_GPS_FSM.d_nav.d_TOW + 2 * GPS_L1_CA_CODE_PERIOD + GPS_CA_PREAMBLE_DURATION_S;
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d_TOW_at_current_symbol = floor(d_TOW_at_Preamble * 1000.0) / 1000.0;
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flag_TOW_set = true;
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d_flag_new_tow_available = false;
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}
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else
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{
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d_TOW_at_current_symbol = d_TOW_at_current_symbol + GPS_L1_CA_CODE_PERIOD;
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}
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current_symbol.TOW_at_current_symbol_s = d_TOW_at_current_symbol;
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current_symbol.Flag_valid_word = flag_TOW_set;
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if (flag_PLL_180_deg_phase_locked == true)
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{
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//correct the accumulated phase for the Costas loop phase shift, if required
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current_symbol.Carrier_phase_rads += GPS_PI;
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}
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if(d_dump == true)
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{
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// MULTIPLEXED FILE RECORDING - Record results to file
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try
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{
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double tmp_double;
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unsigned long int tmp_ulong_int;
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tmp_double = d_TOW_at_current_symbol;
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d_dump_file.write(reinterpret_cast<char*>(&tmp_double), sizeof(double));
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tmp_ulong_int = current_symbol.Tracking_sample_counter;
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d_dump_file.write(reinterpret_cast<char*>(&tmp_ulong_int), sizeof(unsigned long int));
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tmp_double = d_TOW_at_Preamble;
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d_dump_file.write(reinterpret_cast<char*>(&tmp_double), sizeof(double));
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}
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catch (const std::ifstream::failure & e)
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{
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LOG(WARNING) << "Exception writing observables dump file " << e.what();
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}
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}
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// remove used symbols from history
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if (d_symbol_history.size() > required_symbols)
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{
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d_symbol_history.pop_front();
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}
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//3. Make the output (copy the object contents to the GNURadio reserved memory)
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*out[0] = current_symbol;
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return 1;
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}
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void gps_l1_ca_telemetry_decoder_cc::set_satellite(const Gnss_Satellite & satellite)
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{
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d_satellite = Gnss_Satellite(satellite.get_system(), satellite.get_PRN());
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DLOG(INFO) << "Setting decoder Finite State Machine to satellite " << d_satellite;
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d_GPS_FSM.i_satellite_PRN = d_satellite.get_PRN();
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DLOG(INFO) << "Navigation Satellite set to " << d_satellite;
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}
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void gps_l1_ca_telemetry_decoder_cc::set_channel(int channel)
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{
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d_channel = channel;
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d_GPS_FSM.i_channel_ID = channel;
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DLOG(INFO) << "Navigation channel set to " << channel;
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// ############# ENABLE DATA FILE LOG #################
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if (d_dump == true)
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{
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if (d_dump_file.is_open() == false)
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{
|
|
try
|
|
{
|
|
d_dump_filename = "telemetry";
|
|
d_dump_filename.append(boost::lexical_cast<std::string>(d_channel));
|
|
d_dump_filename.append(".dat");
|
|
d_dump_file.exceptions ( std::ifstream::failbit | std::ifstream::badbit );
|
|
d_dump_file.open(d_dump_filename.c_str(), std::ios::out | std::ios::binary);
|
|
LOG(INFO) << "Telemetry decoder dump enabled on channel " << d_channel
|
|
<< " Log file: " << d_dump_filename.c_str();
|
|
}
|
|
catch (const std::ifstream::failure &e)
|
|
{
|
|
LOG(WARNING) << "channel " << d_channel << " Exception opening trk dump file " << e.what();
|
|
}
|
|
}
|
|
}
|
|
}
|