mirror of https://github.com/gnss-sdr/gnss-sdr
535 lines
22 KiB
C++
535 lines
22 KiB
C++
/*!
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* \file gps_l1_ca_telemetry_decoder_gs.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) 2010-2019 (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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* SPDX-License-Identifier: GPL-3.0-or-later
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*
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* -------------------------------------------------------------------------
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*/
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#include "gps_l1_ca_telemetry_decoder_gs.h"
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#include "gps_ephemeris.h" // for Gps_Ephemeris
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#include "gps_iono.h" // for Gps_Iono
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#include "gps_utc_model.h" // for Gps_Utc_Model
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#include <glog/logging.h>
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#include <gnuradio/io_signature.h>
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#include <pmt/pmt.h> // for make_any
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#include <pmt/pmt_sugar.h> // for mp
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#include <cmath> // for round
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#include <cstring> // for memcpy
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#include <exception> // for exception
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#include <iostream> // for cout
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#include <memory> // for shared_ptr
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#ifdef COMPILER_HAS_ROTL
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#include <bit>
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namespace my_rotl = std;
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#else
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namespace my_rotl
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{
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#if HAS_GENERIC_LAMBDA
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auto rotl = [](auto x, auto n) { return (((x) << (n)) ^ ((x) >> (32 - (n)))); };
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#else
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auto rotl = [](uint32_t x, uint32_t n) { return (((x) << (n)) ^ ((x) >> (32 - (n)))); };
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#endif
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} // namespace my_rotl
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#endif
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gps_l1_ca_telemetry_decoder_gs_sptr
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gps_l1_ca_make_telemetry_decoder_gs(const Gnss_Satellite &satellite, bool dump)
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{
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return gps_l1_ca_telemetry_decoder_gs_sptr(new gps_l1_ca_telemetry_decoder_gs(satellite, dump));
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}
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gps_l1_ca_telemetry_decoder_gs::gps_l1_ca_telemetry_decoder_gs(
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const Gnss_Satellite &satellite,
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bool dump) : gr::block("gps_navigation_gs", 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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// prevent telemetry symbols accumulation in output buffers
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this->set_max_noutput_items(1);
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// Ephemeris data port out
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this->message_port_register_out(pmt::mp("telemetry"));
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// Control messages to tracking block
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this->message_port_register_out(pmt::mp("telemetry_to_trk"));
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d_last_valid_preamble = 0;
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d_sent_tlm_failed_msg = false;
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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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DLOG(INFO) << "Initializing GPS L1 TELEMETRY DECODER";
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d_bits_per_preamble = GPS_CA_PREAMBLE_LENGTH_BITS;
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d_samples_per_preamble = d_bits_per_preamble;
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d_preamble_period_symbols = GPS_SUBFRAME_BITS;
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// set the preamble
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d_required_symbols = GPS_SUBFRAME_BITS;
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// preamble bits to sampled symbols
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d_frame_length_symbols = GPS_SUBFRAME_BITS * GPS_CA_TELEMETRY_SYMBOLS_PER_BIT;
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d_max_symbols_without_valid_frame = d_required_symbols * 20; // rise alarm 120 segs without valid tlm
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int32_t n = 0;
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for (int32_t i = 0; i < d_bits_per_preamble; i++)
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{
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if (GPS_CA_PREAMBLE[i] == '1')
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{
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d_preamble_samples[n] = 1;
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n++;
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}
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else
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{
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d_preamble_samples[n] = -1;
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n++;
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}
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}
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d_sample_counter = 0ULL;
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d_stat = 0;
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d_preamble_index = 0ULL;
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d_flag_frame_sync = false;
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d_flag_parity = false;
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d_TOW_at_current_symbol_ms = 0;
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d_TOW_at_Preamble_ms = 0;
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d_CRC_error_counter = 0;
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d_flag_preamble = false;
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d_channel = 0;
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d_flag_TOW_set = false;
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d_flag_PLL_180_deg_phase_locked = false;
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d_prev_GPS_frame_4bytes = 0;
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d_symbol_history.set_capacity(d_required_symbols);
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}
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gps_l1_ca_telemetry_decoder_gs::~gps_l1_ca_telemetry_decoder_gs()
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{
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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_gs::gps_word_parityCheck(uint32_t gpsword)
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{
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uint32_t d1;
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uint32_t d2;
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uint32_t d3;
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uint32_t d4;
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uint32_t d5;
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uint32_t d6;
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uint32_t d7;
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uint32_t t;
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uint32_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-200K. This avoids lengthy shift-
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// and-xor loops.
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d1 = gpsword & 0xFBFFBF00U;
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d2 = my_rotl::rotl(gpsword, 1U) & 0x07FFBF01U;
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d3 = my_rotl::rotl(gpsword, 2U) & 0xFC0F8100U;
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d4 = my_rotl::rotl(gpsword, 3U) & 0xF81FFE02U;
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d5 = my_rotl::rotl(gpsword, 4U) & 0xFC00000EU;
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d6 = my_rotl::rotl(gpsword, 5U) & 0x07F00001U;
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d7 = my_rotl::rotl(gpsword, 6U) & 0x00003000U;
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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 ^ my_rotl::rotl(t, 6U) ^ my_rotl::rotl(t, 12U) ^ my_rotl::rotl(t, 18U) ^ my_rotl::rotl(t, 24U);
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parity = parity & 0x3FU;
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if (parity == (gpsword & 0x3FU))
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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_gs::set_satellite(const Gnss_Satellite &satellite)
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{
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d_nav = Gps_Navigation_Message();
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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.set_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_gs::set_channel(int32_t channel)
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{
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d_channel = channel;
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d_nav.set_channel(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_gs::decode_subframe()
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{
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std::array<char, GPS_SUBFRAME_LENGTH> subframe{};
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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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bool subframe_synchro_confirmation = true;
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for (float subframe_symbol : d_symbol_history)
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{
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// ******* SYMBOL TO BIT *******
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// symbol to bit
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if (subframe_symbol > 0)
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{
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GPS_frame_4bytes += 1; // insert the telemetry bit in LSB
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}
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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 & 0x00000001U)
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{
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GPS_frame_4bytes = GPS_frame_4bytes | 0x40000000U;
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}
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if (d_prev_GPS_frame_4bytes & 0x00000002U)
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{
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GPS_frame_4bytes = GPS_frame_4bytes | 0x80000000U;
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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 & 0x40000000U)
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{
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GPS_frame_4bytes ^= 0x3FFFFFC0U; // invert the data bits (using XOR)
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}
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// check parity. If ANY word inside the subframe fails the parity, set subframe_synchro_confirmation = false
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if (not gps_l1_ca_telemetry_decoder_gs::gps_word_parityCheck(GPS_frame_4bytes))
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{
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subframe_synchro_confirmation = 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 <<= 1U; // shift 1 bit left the telemetry word
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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 (subframe_synchro_confirmation)
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{
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int32_t subframe_ID = d_nav.subframe_decoder(subframe.data()); // decode 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.get_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.get_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.get_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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return true;
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}
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}
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return false;
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}
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void gps_l1_ca_telemetry_decoder_gs::reset()
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{
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gr::thread::scoped_lock lock(d_setlock); // require mutex with work function called by the scheduler
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d_last_valid_preamble = d_sample_counter;
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d_sent_tlm_failed_msg = false;
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d_flag_TOW_set = false;
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d_symbol_history.clear();
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d_stat = 0;
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DLOG(INFO) << "Telemetry decoder reset for satellite " << d_satellite;
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}
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int gps_l1_ca_telemetry_decoder_gs::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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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{};
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// 1. Copy the current tracking output
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current_symbol = in[0][0];
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// add new symbol to the symbol queue
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d_symbol_history.push_back(current_symbol.Prompt_I);
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d_sample_counter++; // count for the processed symbols
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consume_each(1);
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d_flag_preamble = false;
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// check if there is a problem with the telemetry of the current satellite
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if (d_stat < 2 and d_sent_tlm_failed_msg == false)
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{
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if ((d_sample_counter - d_last_valid_preamble) > d_max_symbols_without_valid_frame)
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{
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int message = 1; // bad telemetry
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this->message_port_pub(pmt::mp("telemetry_to_trk"), pmt::make_any(message));
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d_sent_tlm_failed_msg = true;
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}
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}
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// ******* frame sync ******************
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switch (d_stat)
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{
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case 0: // no preamble information
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{
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// correlate with preamble
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int32_t corr_value = 0;
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if (d_symbol_history.size() >= GPS_CA_PREAMBLE_LENGTH_BITS)
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{
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// ******* preamble correlation ********
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for (int32_t i = 0; i < GPS_CA_PREAMBLE_LENGTH_BITS; i++)
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{
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if (d_symbol_history[i] < 0.0) // symbols clipping
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{
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corr_value -= d_preamble_samples[i];
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}
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else
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{
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corr_value += d_preamble_samples[i];
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}
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}
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}
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if (abs(corr_value) >= d_samples_per_preamble)
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{
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d_preamble_index = d_sample_counter; // record the preamble sample stamp
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DLOG(INFO) << "Preamble detection for GPS L1 satellite " << this->d_satellite;
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decode_subframe();
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d_stat = 1; // enter into frame pre-detection status
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}
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d_flag_TOW_set = false;
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break;
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}
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case 1: // possible preamble lock
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{
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// correlate with preamble
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int32_t corr_value = 0;
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int32_t preamble_diff = 0;
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if (d_symbol_history.size() >= GPS_CA_PREAMBLE_LENGTH_BITS)
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{
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// ******* preamble correlation ********
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for (int32_t i = 0; i < GPS_CA_PREAMBLE_LENGTH_BITS; i++)
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{
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if (d_symbol_history[i] < 0.0) // symbols clipping
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{
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corr_value -= d_preamble_samples[i];
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}
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else
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{
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corr_value += d_preamble_samples[i];
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}
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}
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}
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if (abs(corr_value) >= d_samples_per_preamble)
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{
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// check preamble separation
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preamble_diff = static_cast<int32_t>(d_sample_counter - d_preamble_index);
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if (abs(preamble_diff - d_preamble_period_symbols) == 0)
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{
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DLOG(INFO) << "Preamble confirmation for SAT " << this->d_satellite;
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d_preamble_index = d_sample_counter; // record the preamble sample stamp
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if (corr_value < 0)
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{
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d_flag_PLL_180_deg_phase_locked = true;
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}
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else
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{
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d_flag_PLL_180_deg_phase_locked = false;
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}
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decode_subframe();
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d_stat = 2;
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}
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else
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{
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if (preamble_diff > d_preamble_period_symbols)
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{
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d_stat = 0; // start again
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d_flag_TOW_set = false;
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}
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}
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}
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break;
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}
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case 2: // preamble acquired
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{
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if (d_sample_counter >= d_preamble_index + static_cast<uint64_t>(d_preamble_period_symbols))
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{
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DLOG(INFO) << "Preamble received for SAT " << this->d_satellite << "d_sample_counter=" << d_sample_counter << "\n";
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// call the decoder
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// 0. fetch the symbols into an array
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d_preamble_index = d_sample_counter; // record the preamble sample stamp (t_P)
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if (decode_subframe())
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{
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d_CRC_error_counter = 0;
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d_flag_preamble = true; // valid preamble indicator (initialized to false every work())
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gr::thread::scoped_lock lock(d_setlock);
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d_last_valid_preamble = d_sample_counter;
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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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DLOG(INFO) << " Frame sync SAT " << this->d_satellite;
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}
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}
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else
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{
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d_CRC_error_counter++;
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|
if (d_CRC_error_counter > 2)
|
|
{
|
|
DLOG(INFO) << "Lost of frame sync SAT " << this->d_satellite;
|
|
d_flag_frame_sync = false;
|
|
d_stat = 0;
|
|
d_TOW_at_current_symbol_ms = 0;
|
|
d_TOW_at_Preamble_ms = 0;
|
|
d_CRC_error_counter = 0;
|
|
d_flag_TOW_set = false;
|
|
}
|
|
}
|
|
}
|
|
break;
|
|
}
|
|
}
|
|
|
|
// 2. Add the telemetry decoder information
|
|
if (d_flag_preamble == true)
|
|
{
|
|
if (!(d_nav.get_TOW() == 0))
|
|
{
|
|
d_TOW_at_current_symbol_ms = static_cast<uint32_t>(d_nav.get_TOW() * 1000.0);
|
|
d_TOW_at_Preamble_ms = static_cast<uint32_t>(d_nav.get_TOW() * 1000.0);
|
|
d_flag_TOW_set = true;
|
|
}
|
|
else
|
|
{
|
|
DLOG(INFO) << "Received GPS L1 TOW equal to zero at sat " << d_nav.get_satellite_PRN();
|
|
}
|
|
}
|
|
else
|
|
{
|
|
if (d_flag_TOW_set == true)
|
|
{
|
|
d_TOW_at_current_symbol_ms += GPS_L1_CA_BIT_PERIOD_MS;
|
|
}
|
|
}
|
|
|
|
if (d_flag_TOW_set == true)
|
|
{
|
|
current_symbol.TOW_at_current_symbol_ms = d_TOW_at_current_symbol_ms;
|
|
current_symbol.Flag_valid_word = d_flag_TOW_set;
|
|
|
|
if (d_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 GNU Radio reserved memory)
|
|
*out[0] = current_symbol;
|
|
|
|
return 1;
|
|
}
|
|
|
|
return 0;
|
|
}
|