ogrt_riseset.c

The OpenGPSRec receiver software runs on the real time operating system RTAI-Linux. It compiles with

/* ************************************************************************ 
   *                                                                      *
   *                            OpenGPS Receiver                          *
   *                                                                      *
   * -------------------------------------------------------------------- *
   *                                                                      *
   *    Module:   ogrt_riseset.c                                          *
   *                                                                      *
   *   Version:   0.1                                                     *
   *                                                                      *
   *      Date:   09.12.02                                                *
   *                                                                      *
   *    Author:   C. Kelley, G. Beyerle                                   *
   *                                                                      *
   * -------------------------------------------------------------------- *
   *                                                                      *
   * Copyright (C) 2001-2003  C. Kelley, G. Beyerle                       *
   *                                                                      *
   * This program 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 2 of the License, or    *
   * (at your option) any later version.                                  *
   *                                                                      *
   * This program 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 program; if not, write to the Free Software          *
   * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.            *
   *                                                                      *
   * -------------------------------------------------------------------- *
   *                                                                      *
   * OpenGPS is based on Clifford Kelley's OpenSourceGPS distribution.    *
   * The OpenSourceGPS distribution can be obtained from                  *
   *             http://www.home.earthlink.net/~cwkelley                  *
   *                                                                      *
   * -------------------------------------------------------------------- *
   *                                                                      *
   *                         Real-time process                            *
   *                                                                      *
   ************************************************************************ */

/* ******************************* changes ********************************

   26.01.03 - replace 'trackch' by 'RT_Ctrl->leadch'
              use fields RT_Ctrl->accum_missed & ->accum_new
   18.07.03 - Chan[].ms_count wraps at 6000 (instead of 30000)
   18.07.03 - move Ms_Count to struct Chan[]
   31.07.03 - fixed bug in find/read_preamble()
   03.08.03 - copy carrier-aided code tracking from OpenSourceGPS

   ************************************************************************ */

/***********************************************************************
  GPS RECEIVER (GPSRCVR) Ver. 1.02
  12 Channel All-in-View GPS Receiver Program based on 
  Mitel GP2021 chipset
  Clifford Kelley [e-mail]
  Copyright (c) 1996-2002 Clifford Kelley.  All Rights Reserved.
  This LICENSE must be included with the OGR code.
***********************************************************************/

/*
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

      CONDITIONS

1. Redistributions of GPSRCVR source code must retain the above copyright
notice, this list of conditions, and the following disclaimer.

2. Redistributions in binary form must contain the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.

3. All modifications to the source code must be clearly marked as
such.  Binary redistributions based on modified source code must be
clearly marked as modified versions in the documentation and/or other
materials provided with the distribution.

4. Notice must be given of the location of the availability of the
unmodified current source code, e.g.,
  http://www.Kelley.com/
or
  ftp://ftp.Kelley.com
in the documentation and/or other materials provided with the
distribution.

5. All advertising and published materials mentioning features or use
of this software must display the following acknowledgment:  "This
product includes software developed by Clifford Kelley and other
contributors."

6. The name of Clifford Kelley may not be used to endorse or promote
products derived from this software without specific prior written
permission.

      DISCLAIMER

This software is provided by Clifford Kelley and contributors "as is" and
any expressed or implied warranties, including, but not limited to, the
implied warranties of merchantability and fitness for a particular
purpose are disclaimed.  In no event shall Clifford Kelley or
contributors be liable for any direct, indirect, incidental, special,
exemplary, or consequential damages (including, but not limited to,
procurement of substitute goods or services; loss of use, data, or
profits; or business interruption) however caused and on any theory of
liability, whether in contract, strict liability, or tort (including
negligence or otherwise) arising in any way out of the use of this
software, even if advised of the possibility of such damage.
*/

/* ------------------------------- includes ------------------------------- */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>

#include <rtai.h>
#include <rtai_sched.h>
#include <rtai_fifos.h>
#include <rtai_shm.h>

#include  "port.h"
#include  "ogr_defines.h"
#include  "ogr_structs.h"

#include  "ogrt_defines.h"
#include  "ogrt_globals.h"
#include  "ogrt_prototypes.h"

MODULE_LICENSE( "GPL");

/* ------------------------------- defines -------------------------------- */

/* ------------------------------ globals --------------------------------- */

//static long delta_carrier[NOFCHN], delta_code[NOFCHN];

/* ------------------------------ prototypes ------------------------------ */

/* ------------------------------ procedures ------------------------------ */

/* ------------------------------------------------------------------------- *
FUNCTION init_risesetriseset()
RETURNS  None.

PARAMETERS
  ch   channel number (0-11)

PURPOSE
  init 'riseset' and 'riseset' modes: all 12 channels track
  the same PRN tracked by channel no. 'RT_Ctrl->leadch'
* ------------------------------------------------------------------------- */

/* ------------------------------------------------------------------------- *
FUNCTION ch_track_riseset()
RETURNS  None.

PARAMETERS
  ch   : channel number

PURPOSE
  track signal in code and doppler space
  write inphase / quad data to user prg via FIFO

WRITTEN BY
  Clifford Kelley
* ------------------------------------------------------------------------- */

void ch_track_riseset( INT16 ch, INT16 accum_missed)
{
  INT16 bit;
  long  i_sum, q_sum, dfrq, 
        car_phs_res, cod_phs_res,
        prompt_mag, dith_mag;

  if ( ch != RT_Ctrl->leadch)
    return;

//  GP2021 has two tracking arms only: prompt & dither
  i_sum = Chan[ch].i_prompt + Chan[ch].i_dith;
  q_sum = Chan[ch].q_prompt + Chan[ch].q_dith;

/*  
 *  phase discriminator: atan( Q, I), we can't use atan2() here, since data bits
 *  are still modulated on the signal causing sign flips.
 */
  car_phs_res = fix_atan( q_sum, i_sum);

/* --- 2nd order PLL --- */
  dfrq = trk_car_c3 * car_phs_res - 
         trk_car_c1 * car_phs_res_prv[ch];

/* --- save residual phase for next iteration --- */
  car_phs_res_prv[ch] = car_phs_res;

/* --- fix point arithmetics (2^14 <-> 1.0) --- */
  Chan[ch].car_frq += dfrq >> 14;

/*
 *  update carrier frq (all channels simultaneously!)
 */
  all_carrier( Chan[ch].car_frq);
//  ch_carrier( ch, Chan[ch].car_frq);

#if 0
//  adjust carrier frqs of trailing channels every TIC event only
  rt_printk( "ch_track_riseset: delta_carrier[%d] = %ld\n", ch, delta_carrier[ch]);
  if ( accum_missed & 0x2000)
  {
    int i;
    for ( i=0; i<NOFCHN; i++)
    {
      rt_printk( "ch_track_riseset: (2) delta_carrier[i] = %ld\n", delta_carrier[i]);
      if ( i != ch)
        ch_carrier( i, Chan[ch].car_frq - delta_carrier[i]);
    }
  }
#endif


/*
 *  average over 20ms
 */
  Chan[ch].q_dith_20ms   += Chan[ch].q_dith;
  Chan[ch].q_prompt_20ms += Chan[ch].q_prompt;
  Chan[ch].i_dith_20ms   += Chan[ch].i_dith;
  Chan[ch].i_prompt_20ms += Chan[ch].i_prompt;

/*
 *  we've added 20 samples
 */
  if ( ( Chan[ch].ms_count % 20) == 0)
  {
    prompt_mag = rss( Chan[ch].i_prompt_20ms, Chan[ch].q_prompt_20ms);
    dith_mag   = rss( Chan[ch].i_dith_20ms,   Chan[ch].q_dith_20ms);

    cod_phs_res = RT_Ctrl->earlylate * ( prompt_mag - 2 * dith_mag);

/* --- 2nd order PLL --- */
    dfrq = trk_cod_c3 * cod_phs_res - 
           trk_cod_c1 * cod_phs_res_prv[ch];

/* --- save for next iteration --- */
    cod_phs_res_prv[ch] = cod_phs_res;

/* --- fix point arithmetics (2^14 <-> 1.0) --- */
    Chan[ch].cod_frq += dfrq >> 14;

//  update code frq
    all_code( Chan[ch].cod_frq);

#if 0
//  shift slave channels at TIC rate (0.1 s) only
      if ( accum_missed & 0x2000)
      {
        int i;
        for ( i=0; i<NOFCHN; i++)
        {
          if ( i != ch)
            ch_code( i, Chan[ch].cod_frq - delta_code[i]);
        }
      }
#endif

//    Chan[ch].sum += Chan[ch].prompt_mag + Chan[ch].dith_mag;
//
//    if ( Chan[ch].ms_count % 100 == 0)
//    {
//      Chan[ch].avg_20ms = Chan[ch].sum / 5;
//      Chan[ch].sum      = 0;
//    }

//  nav bit
    bit = BSIGN( Chan[ch].i_prompt_20ms + Chan[ch].i_dith_20ms);

/* 
 *  Find preamble if not yet found. If already found, just read it.
 */
    if ( !Chan[ch].tow_sync)
      find_preamble( ch, bit);
    else
      read_preamble( ch, bit);

/* 
 *  Variable 'Preamble_Found[]' is set in find_preamble()
 */
    if ( Preamble_Found[ch])
      writefifo_navbit( ch, bit);

    writefifo_corrdata( ch, ch);  // in riseset mode, ch == RT_Ctrl->leadch!

    Chan[ch].q_dith_20ms   = 0;
    Chan[ch].q_prompt_20ms = 0;
    Chan[ch].i_dith_20ms   = 0;
    Chan[ch].i_prompt_20ms = 0;

  }  // --- if ( msec_count[ch] ... ) ---

//  we count bits & frames only in tracking mode
  if ( Chan[ch].ms_count % 20 == 0)
    Chan[ch].bit_count = (Chan[ch].bit_count + 1) % 1500;

  if ( Chan[ch].ms_count == 0 && Chan[ch].sfid == 5)
    Chan[ch].frame_count += 1;

  return;
}

/* ------------------------------------------------------------------------- *
FUNCTION ch_follow_riseset_DUMP()

RETURNS
  none

PARAMETERS
  ch  : channel number
  idx : index in channel_list + 1 (1,...,11)

PURPOSE
  in 'riseset' mode 11 'slave' channels follow 1 'master' channel,
  add amplitudes at DUMP event
* ------------------------------------------------------------------------- */

void ch_follow_riseset_DUMP( INT16 ch)
{
  INT16 leadch;
  
/* 
 * don't touch the master channel!
 */
  if ( ch == RT_Ctrl->leadch)
    return;

  leadch = RT_Ctrl->leadch;

// code_phase : 0,...,2045; halfchips
// code_DCO_phase : 0,...,1023; 1/1024 halfchip
//  Ofs = (Chan[ch].code_phase - Chan[RT_Ctrl->leadch].code_phase)*1024 + 
//        (Chan[ch].code_DCO_phase - Chan[RT_Ctrl->leadch].code_DCO_phase);

//  keep track of I/Q
  Chan[ch].q_dith_20ms   += Chan[ch].q_dith;
  Chan[ch].q_prompt_20ms += Chan[ch].q_prompt;
  Chan[ch].i_dith_20ms   += Chan[ch].i_dith;
  Chan[ch].i_prompt_20ms += Chan[ch].i_prompt;

  if ( ( Chan[leadch].ms_count % 20) == 0)
  {
    writefifo_corrdata( ch, leadch);

    Chan[ch].q_dith_20ms   = 0;
    Chan[ch].q_prompt_20ms = 0;
    Chan[ch].i_dith_20ms   = 0;
    Chan[ch].i_prompt_20ms = 0;
  }

  return;
 
}

/* ------------------------------------------------------------------------- *
FUNCTION ch_follow_riseset_TIC()

RETURNS
  none

PARAMETERS
  ch  : channel number
  idx : index in channel_list + 1 (1,...,11)

PURPOSE
  in 'riseset' mode 11 'slave' channels follow 1 'master' channel,
  keep synchronization
  Correct code/carrier DCO frequencies at TICs only.
* ------------------------------------------------------------------------- */

void ch_follow_riseset_TIC( INT16 leadch)
{
  INT16 ch;
  long  delta;


  for ( ch=0; ch<NOFCHN; ch++)
  {

// don't touch the master channel
    if ( ch == leadch)
      continue;

  //  first align in carrier space ...
    if ( Chan[ch].carr_dco_phase <= 1023 && Chan[leadch].carr_dco_phase <= 1023)
    {

      delta = Chan[ch].carr_dco_phase - Chan[leadch].carr_dco_phase;

  /* 
   * delta : -1023,...,1-,0,1,...,1023
   * map to interval -512,...,512 
   */
      delta = ((delta + 1024 + 512) % 1024) - 512;

  /*
   *  positive phase difference -> run slower
   *  negative phase difference -> run faster
   */

  /*
   * deviate somewhat from master's frequency to re-sync
   */
      ch_carrier( ch, Chan[leadch].car_frq - 10 * delta);

    }

  /* 
   * ... then align in code space
   *  Chan[ch].code_phase     = 0,...,2045   [halfchips]
   *  Chan[ch].code_dco_phase = 0,...,1023   [1/1024 halfchips]
   */

  /*
   *  ignore outlier values
   */
    if ( Chan[ch].code_phase <= 2047 && Chan[ch].code_dco_phase <= 1023 &&
         Chan[leadch].code_phase <= 2047 && Chan[leadch].code_dco_phase <= 1023)
    {
      delta = 
        (Chan[ch].code_phase     * 1024L + Chan[ch].code_dco_phase) - 
        (Chan[leadch].code_phase * 1024L + Chan[leadch].code_dco_phase);

  // delta : -2046*1024,...,1-,0,1,...,2046*1024
  //    delta = ( delta >  1023L * 1024L) ? delta - 2046L * 1024L : delta;
  //    delta = ( delta < -1023L * 1024L) ? delta + 2046L * 1024L : delta;

      delta = ((delta + 2046L * 1024L + 1023L * 1024L) % (2046L * 1024L)) - 1023L * 1024L;

  // add offsets to spread slave channels in code space
//      delta += riseset_cod_ofs[ch];
      delta = 0;

  /*
   * update code and carrier NCOs to keep them in sync
   */
      ch_code( ch, Chan[leadch].cod_frq - delta);
    }  
  }  // --- for ( ch=0; ch<NOFCHN; ch++) ---  
  
  return;
}


/* ------------------------------- end of file ---------------------------- */