gps_despread_impl.h

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/* -*- c++ -*- */
/* 
 * Copyright 2014 Samu Laaja.
 * 
 * This is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3, or (at your option)
 * any later version.
 * 
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this software; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street,
 * Boston, MA 02110-1301, USA.
 */

#ifndef INCLUDED_GPS_GPS_DESPREAD_IMPL_H
#define INCLUDED_GPS_GPS_DESPREAD_IMPL_H

#define DEBUG_OUT
#define MAX_SEARCH_THREADS 4


#define FREQ_SAMPLING_RATE 4

#include <gps/gps_despread.h>
#include <gnuradio/fft/fft.h>
#include <stdio.h>


typedef enum
{
        state_start_search,
        state_wait_search,
        state_track
} fsm_state;

typedef struct 
{
        // inputs
        gr_complex *data;
        gr_complex *code_LUT;
        int osr;
        int data_len;
        int freq_search_Nsteps;

        // outputs
        int best_delay;
        float best_freq;
        float snr;

        int done;
        int running;
        
} search_data_t;

namespace gr {
  namespace gps {

    class gps_despread_impl : public gps_despread
    {
        private:

                // code generator
                gr_complex code_LUT[1023][32];
                int code_selection;
                int code_counter;
                int increment_counter;
                 
                int osr_int;
                 
                int delay_selection;
                 
                 // search
                int freq_search_Nsteps;

                search_data_t search_data;
                pthread_t search_thread;
                int search_acq_counter;

                int search_avg_selection;

                // doppler correction
                float nco_freq;
                float nco_freq_fixed;
                float nco_phase;
        
                // code tracking
                gr_complex track_integrator[5];
                int track_counter;
                int track_mode;
                int lockdet_counter; // PLL lock detection

                // freq tracking
                gr_complex freq_corr_integrator[FREQ_SAMPLING_RATE];
                gr_complex freq_corr_integrator_d[FREQ_SAMPLING_RATE]; 
                gr_complex freq_corr_integrator_filtered[FREQ_SAMPLING_RATE];
                gr_complex freq_corr_integrator_filtered_d;
                int fix_done;
                        
                int freq_Nsamples; // number of frequency samples per code period

                float phase_error;
                float lf_int;
                float lf_zero_d;
                float lf_pole_d;
                float freqerror_trunc_d;

                fsm_state fsm;

                void generate_codes();

                void track(const gr_complex *, gr_complex *, int, int &);
                void update_pll(float);

        public:
                gps_despread_impl(int, int);
                ~gps_despread_impl();

                void set_code(int);
                int code(void) const;
          
                void set_osr(int);
                int osr(void) const;
          
                void set_freq(float);

                void set_delay(int);
                int delay(void) const;
          
                void start_search();
        
                void forecast(int, gr_vector_int &);
      // Where all the action really happens
                int general_work(int, gr_vector_int &, gr_vector_const_void_star &, gr_vector_void_star &);
    };

  } // namespace gps
} // namespace gr

#endif /* INCLUDED_GPS_GPS_DESPREAD_IMPL_H */