gps_l1_ca_telemetry_decoder_gs.h

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/*!
 * \file gps_l1_ca_telemetry_decoder_gs.h
 * \brief Interface of a NAV message demodulator block based on
 * Kay Borre book MATLAB-based GPS receiver
 * \author Javier Arribas, 2011. jarribas(at)cttc.es
 * \author Carles Fernandez Prades, 2011-2026. cfernandez(at)cttc.es
 *
 * -----------------------------------------------------------------------------
 *
 * GNSS-SDR is a Global Navigation Satellite System software-defined receiver.
 * This file is part of GNSS-SDR.
 *
 * Copyright (C) 2010-2026  (see AUTHORS file for a list of contributors)
 * SPDX-License-Identifier: GPL-3.0-or-later
 *
 * -----------------------------------------------------------------------------
 */

#ifndef GNSS_SDR_GPS_L1_CA_TELEMETRY_DECODER_GS_H
#define GNSS_SDR_GPS_L1_CA_TELEMETRY_DECODER_GS_H

#include "GPS_L1_CA.h"
#include "gnss_synchro.h"
#include "gnss_time.h"  // for timetags produced by Tracking
#include "gps_navigation_message.h"
#include "nav_message_packet.h"
#include "telemetry_impl_interface.h"
#include "tlm_conf.h"
#include <boost/circular_buffer.hpp>
#include <gnuradio/types.h>  // for gr_vector_const_void_star
#include <array>             // for array


/** \addtogroup Telemetry_Decoder
 * \{ */
/** \addtogroup Telemetry_Decoder_gnuradio_blocks telemetry_decoder_gr_blocks
 * GNU Radio blocks for the demodulation of GNSS navigation messages.
 * \{ */

enum class L1LnavSystem
{
    GPS,
    QZSS
};

class gps_l1_ca_telemetry_decoder_gs;

using gps_l1_ca_telemetry_decoder_gs_sptr = gnss_shared_ptr<gps_l1_ca_telemetry_decoder_gs>;

gps_l1_ca_telemetry_decoder_gs_sptr gps_l1_ca_make_telemetry_decoder_gs(
    const Gnss_Satellite &satellite,
    const Tlm_Conf &conf,
    L1LnavSystem system = L1LnavSystem::GPS);

/*!
 * \brief This class implements a block that decodes the NAV data defined in IS-GPS-200M
 */
class gps_l1_ca_telemetry_decoder_gs : public telemetry_impl_interface
{
public:
    ~gps_l1_ca_telemetry_decoder_gs() override;
    void set_satellite(const Gnss_Satellite &satellite) override;  //!< Set satellite PRN
    void set_channel(int channel) override;                        //!< Set receiver's channel
    void reset() override;

    /*!
     * \brief This is where all signal processing takes place
     */
    int general_work(int noutput_items, gr_vector_int &ninput_items,
        gr_vector_const_void_star &input_items, gr_vector_void_star &output_items) override;

private:
    friend gps_l1_ca_telemetry_decoder_gs_sptr gps_l1_ca_make_telemetry_decoder_gs(
        const Gnss_Satellite &satellite,
        const Tlm_Conf &conf,
        L1LnavSystem system);

    gps_l1_ca_telemetry_decoder_gs(const Gnss_Satellite &satellite, const Tlm_Conf &conf, L1LnavSystem system);

    void check_tlm_separation();
    void frame_synchronization(const Gnss_Synchro &current_gs);
    bool is_PLL_180_deg_phase_locked();
    bool gps_word_parityCheck(uint32_t gpsword);
    bool decode_subframe(double cn0, bool flag_invert);
    bool is_tow_consistent(uint32_t decoded_tow_s);

    L1LnavSystem d_system;
    std::unique_ptr<Gps_Navigation_Message> d_nav;
    Gnss_Satellite d_satellite;
    Nav_Message_Packet d_nav_msg_packet;
    std::unique_ptr<Tlm_CRC_Stats> d_Tlm_CRC_Stats;

    std::array<int32_t, GPS_CA_PREAMBLE_LENGTH_BITS> d_preamble_samples{};

    std::string d_dump_filename;
    std::ofstream d_dump_file;

    boost::circular_buffer<float> d_symbol_history;

    uint64_t d_sample_counter;
    uint64_t d_preamble_index;
    uint64_t d_last_valid_preamble;

    int32_t d_bits_per_preamble;
    int32_t d_samples_per_preamble;
    int32_t d_preamble_period_symbols;
    int32_t d_CRC_error_counter;
    int32_t d_channel;

    uint32_t d_required_symbols;
    uint32_t d_prev_GPS_frame_4bytes;
    uint32_t d_max_symbols_without_valid_frame;
    uint32_t d_stat;
    uint32_t d_TOW_at_Preamble_ms;
    uint32_t d_TOW_at_current_symbol_ms;
    uint32_t d_last_decoded_tow_s;
    uint64_t d_last_decoded_tow_sample_counter;

    bool d_flag_frame_sync;
    bool d_flag_preamble;
    bool d_sent_tlm_failed_msg;
    bool d_flag_PLL_180_deg_phase_locked;
    bool d_flag_TOW_set;
    bool d_dump;
    bool d_dump_mat;
    bool d_remove_dat;
    bool d_enable_navdata_monitor;
    bool d_dump_crc_stats;
    bool d_tow_to_trk;
    bool d_have_last_decoded_tow;
};


/** \} */
/** \} */
#endif  // GNSS_SDR_GPS_L1_CA_TELEMETRY_DECODER_GS_H