mirror of https://github.com/gnss-sdr/gnss-sdr
483 lines
21 KiB
C++
483 lines
21 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) 2010-2018 (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 <https://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 "control_message_factory.h"
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#include <boost/lexical_cast.hpp>
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#include <glog/logging.h>
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#include <gnuradio/io_signature.h>
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#include <volk_gnsssdr/volk_gnsssdr.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) : 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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// 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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uint16_t preambles_bits[GPS_CA_PREAMBLE_LENGTH_BITS] = GPS_PREAMBLE;
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// preamble bits to sampled symbols
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d_preambles_symbols = static_cast<int32_t *>(volk_gnsssdr_malloc(GPS_CA_PREAMBLE_LENGTH_SYMBOLS * sizeof(int32_t), volk_gnsssdr_get_alignment()));
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int32_t n = 0;
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for (uint16_t preambles_bit : preambles_bits)
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{
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for (uint32_t j = 0; j < GPS_CA_TELEMETRY_SYMBOLS_PER_BIT; j++)
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{
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if (preambles_bit == 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 = 0U;
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d_flag_frame_sync = false;
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d_prev_GPS_frame_4bytes = 0;
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d_TOW_at_Preamble_ms = 0;
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flag_TOW_set = false;
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d_flag_preamble = false;
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d_flag_new_tow_available = false;
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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 = 0ULL;
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d_TOW_at_current_symbol_ms = 0;
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d_symbol_history.set_capacity(GPS_CA_PREAMBLE_LENGTH_SYMBOLS);
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d_crc_error_synchronization_counter = 0;
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d_current_subframe_symbol = 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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volk_gnsssdr_free(d_preambles_symbols);
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d_symbol_history.clear();
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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(uint32_t gpsword)
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{
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uint32_t 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))
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{
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return (true);
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}
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return (false);
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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_nav.reset();
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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_nav.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(int32_t channel)
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{
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d_channel = channel;
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d_nav.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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{
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try
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{
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d_dump_filename = "telemetry";
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d_dump_filename.append(std::to_string(d_channel));
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d_dump_filename.append(".dat");
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d_dump_file.exceptions(std::ifstream::failbit | std::ifstream::badbit);
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d_dump_file.open(d_dump_filename.c_str(), std::ios::out | std::ios::binary);
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LOG(INFO) << "Telemetry decoder dump enabled on channel " << d_channel
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<< " Log file: " << d_dump_filename.c_str();
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}
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catch (const std::ifstream::failure &e)
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{
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LOG(WARNING) << "channel " << d_channel << " Exception opening trk dump file " << e.what();
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}
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}
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}
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}
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bool gps_l1_ca_telemetry_decoder_cc::decode_subframe()
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{
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char subframe[GPS_SUBFRAME_LENGTH];
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int32_t symbol_accumulator_counter = 0;
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int32_t frame_bit_index = 0;
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int32_t word_index = 0;
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uint32_t GPS_frame_4bytes = 0;
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float symbol_accumulator = 0;
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bool subframe_synchro_confirmation = false;
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bool CRC_ok = true;
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for (float d_subframe_symbol : d_subframe_symbols)
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{
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// ******* SYMBOL TO BIT *******
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// extended correlation to bit period is enabled in tracking!
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symbol_accumulator += d_subframe_symbol; // accumulate the input value in d_symbol_accumulator
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symbol_accumulator_counter++;
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if (symbol_accumulator_counter == 20)
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{
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// symbol to bit
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if (symbol_accumulator > 0) GPS_frame_4bytes += 1; // insert the telemetry bit in LSB
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symbol_accumulator = 0;
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symbol_accumulator_counter = 0;
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// ******* bits to words ******
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frame_bit_index++;
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if (frame_bit_index == 30)
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{
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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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GPS_frame_4bytes = 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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GPS_frame_4bytes = 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 (GPS_frame_4bytes & 0x40000000)
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{
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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(GPS_frame_4bytes))
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{
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subframe_synchro_confirmation = true;
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}
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else
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{
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// std::cout << "word invalid sat " << this->d_satellite << std::endl;
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CRC_ok = false;
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}
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// add word to subframe
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// insert the word in the correct position of the subframe
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std::memcpy(&subframe[word_index * GPS_WORD_LENGTH], &GPS_frame_4bytes, sizeof(uint32_t));
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word_index++;
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d_prev_GPS_frame_4bytes = GPS_frame_4bytes; // save the actual frame
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GPS_frame_4bytes = 0;
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}
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else
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{
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GPS_frame_4bytes <<= 1; // shift 1 bit left the telemetry word
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}
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}
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}
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// decode subframe
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// NEW GPS SUBFRAME HAS ARRIVED!
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if (CRC_ok)
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{
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int32_t subframe_ID = d_nav.subframe_decoder(subframe); //d ecode the subframe
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if (subframe_ID > 0 and subframe_ID < 6)
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{
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std::cout << "New GPS NAV message received in channel " << this->d_channel << ": "
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<< "subframe "
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<< subframe_ID << " from satellite "
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<< Gnss_Satellite(std::string("GPS"), d_nav.i_satellite_PRN) << std::endl;
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switch (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_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_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_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_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_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_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_flag_new_tow_available = true;
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}
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else
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{
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return false;
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}
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}
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return subframe_synchro_confirmation;
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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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int32_t preamble_diff_ms = 0;
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auto **out = reinterpret_cast<Gnss_Synchro **>(&output_items[0]); // Get the output buffer pointer
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const auto **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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// record the oldest subframe symbol before inserting a new symbol into the circular buffer
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if (d_current_subframe_symbol < GPS_SUBFRAME_MS and !d_symbol_history.empty())
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{
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d_subframe_symbols[d_current_subframe_symbol] = d_symbol_history[0].Prompt_I;
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d_current_subframe_symbol++;
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}
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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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d_flag_preamble = false;
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// ******* preamble correlation ********
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int32_t corr_value = 0;
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if ((d_symbol_history.size() == GPS_CA_PREAMBLE_LENGTH_SYMBOLS)) // and (d_make_correlation or !d_flag_frame_sync))
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{
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// std::cout << "-------\n";
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for (uint32_t i = 0; i < GPS_CA_PREAMBLE_LENGTH_SYMBOLS; i++)
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{
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if (d_symbol_history[i].Flag_valid_symbol_output == true)
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{
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if (d_symbol_history[i].Prompt_I < 0) // symbols clipping
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{
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corr_value -= d_preambles_symbols[i];
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}
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else
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{
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corr_value += d_preambles_symbols[i];
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}
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}
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}
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}
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// ******* frame sync ******************
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if (std::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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// record the preamble sample stamp
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d_preamble_time_samples = d_symbol_history[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[0].Tracking_sample_counter=" << d_symbol_history[0].Tracking_sample_counter;
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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 = std::round(((static_cast<double>(d_symbol_history[0].Tracking_sample_counter) - static_cast<double>(d_preamble_time_samples)) / static_cast<double>(d_symbol_history[0].fs)) * 1000.0);
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if (std::abs(preamble_diff_ms - GPS_SUBFRAME_MS) % GPS_SUBFRAME_MS == 0)
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{
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DLOG(INFO) << "Preamble confirmation for SAT " << this->d_satellite;
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d_flag_preamble = true;
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d_preamble_time_samples = d_symbol_history[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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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[0].fs) << " [s]";
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}
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// try to decode the subframe:
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if (decode_subframe() == false)
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{
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d_crc_error_synchronization_counter++;
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if (d_crc_error_synchronization_counter > 3)
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{
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DLOG(INFO) << "TOO MANY CRC ERRORS: Lost of frame sync SAT " << this->d_satellite << std::endl;
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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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d_crc_error_synchronization_counter = 0;
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}
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}
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d_current_subframe_symbol = 0;
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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[0].Tracking_sample_counter) - static_cast<double>(d_preamble_time_samples)) / static_cast<double>(d_symbol_history[0].fs)) * 1000.0);
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if (preamble_diff_ms > GPS_SUBFRAME_MS)
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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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// std::cout << "Lost of frame sync SAT " << this->d_satellite << " preamble_diff= " << preamble_diff_ms << std::endl;
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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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d_current_subframe_symbol = 0;
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d_crc_error_synchronization_counter = 0;
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d_TOW_at_current_symbol_ms = 0;
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}
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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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d_TOW_at_current_symbol_ms = static_cast<uint32_t>(d_nav.d_TOW * 1000.0) + GPS_CA_PREAMBLE_DURATION_MS;
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d_TOW_at_Preamble_ms = static_cast<uint32_t>(d_nav.d_TOW * 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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if (flag_TOW_set == true)
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{
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d_TOW_at_current_symbol_ms += GPS_L1_CA_CODE_PERIOD_MS;
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}
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}
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if (flag_TOW_set == true)
|
|
{
|
|
current_symbol.TOW_at_current_symbol_ms = d_TOW_at_current_symbol_ms;
|
|
current_symbol.Flag_valid_word = flag_TOW_set;
|
|
|
|
if (flag_PLL_180_deg_phase_locked == true)
|
|
{
|
|
// correct the accumulated phase for the Costas loop phase shift, if required
|
|
current_symbol.Carrier_phase_rads += GPS_PI;
|
|
}
|
|
|
|
if (d_dump == true)
|
|
{
|
|
// MULTIPLEXED FILE RECORDING - Record results to file
|
|
try
|
|
{
|
|
double tmp_double;
|
|
uint64_t tmp_ulong_int;
|
|
tmp_double = static_cast<double>(d_TOW_at_current_symbol_ms) / 1000.0;
|
|
d_dump_file.write(reinterpret_cast<char *>(&tmp_double), sizeof(double));
|
|
tmp_ulong_int = current_symbol.Tracking_sample_counter;
|
|
d_dump_file.write(reinterpret_cast<char *>(&tmp_ulong_int), sizeof(uint64_t));
|
|
tmp_double = static_cast<double>(d_TOW_at_Preamble_ms) / 1000.0;
|
|
d_dump_file.write(reinterpret_cast<char *>(&tmp_double), sizeof(double));
|
|
}
|
|
catch (const std::ifstream::failure &e)
|
|
{
|
|
LOG(WARNING) << "Exception writing observables dump file " << e.what();
|
|
}
|
|
}
|
|
|
|
// 3. Make the output (copy the object contents to the GNURadio reserved memory)
|
|
*out[0] = current_symbol;
|
|
|
|
return 1;
|
|
}
|
|
|
|
|
|
return 0;
|
|
}
|