galmon/glonass.hh

#pragma once
#include <bitset>
#include <string>
#include <map>
#include "bits.hh"
#include <iostream>
std::basic_string<uint8_t> getGlonassessage(std::basic_string_view<uint8_t> payload);

struct GlonassMessage
{
  uint8_t strtype;

  int parse(std::basic_string_view<uint8_t> gstr)
  {
    strtype = getbitu(&gstr[0], 1, 4);
    if(strtype == 1) {
      parse1(gstr);
    }
    else if(strtype == 2) {
      parse2(gstr);
    }
    else if(strtype == 3) {
      parse3(gstr);
    }
    else if(strtype == 4) {
      parse4(gstr);
    }
    else if(strtype == 5) {
      parse5(gstr);
    }

    return strtype;
  }

  /* The GLONASS day starts at 00:00 Moscow time, which is on UTC+3 by definition.
     This means midnight is 21:00 UTC the previous day.
     Various GLONASS things relate to "the day", so it is important to note which day we are at
  */
  uint8_t hour, minute, seconds, P1;
  int32_t x, dx, ddx;
  
  void parse1(std::basic_string_view<uint8_t> gstr)
  {
    hour = getbitu(&gstr[0], 9, 5);
    minute = getbitu(&gstr[0], 14, 6);
    seconds = 30*getbitu(&gstr[0], 20, 1);
    P1 = getbitu(&gstr[0], 85-78, 2);
    x=getbitsglonass(&gstr[0], 85-35, 27); // 2^-11
    dx=getbitsglonass(&gstr[0], 85-64, 24); // 2^-20
    ddx=getbitsglonass(&gstr[0], 85-40, 5); // 2^-30
  }

  uint8_t Bn, Tb, P2;
  int32_t y, dy, ddy;

  /* The GLONASS ephemeris centered on the "Tb-th" interval, from the start of the Moscow day.
     An interval is 15 minutes long, plus a spacer of length described by P1. If P1 is zero, there is no spacer.
  */
  
  void parse2(std::basic_string_view<uint8_t> gstr)
  {
    Bn = getbitu(&gstr[0], 85-80, 3); // Health bit, only look at MSB, ignore the rest. 0 is ok.
    Tb = getbitu(&gstr[0], 85-76, 7); 
    P2 = getbitu(&gstr[0], 85-77, 1);
    
    y=getbitsglonass(&gstr[0], 85-35, 27); // 2^-11, in kilometers
    dy=getbitsglonass(&gstr[0], 85-64, 24); // 2^-20, in kilometers
    ddy=getbitsglonass(&gstr[0], 85-40, 5); // 2^-30, in kilometers
    
  }

  int32_t z, dz, ddz;


  bool P, P3;
  uint16_t gamman;
  void parse3(std::basic_string_view<uint8_t> gstr)
  {
    z   = getbitsglonass(&gstr[0], 85-35, 27); // 2^-11
    dz  = getbitsglonass(&gstr[0], 85-64, 24); // 2^-20
    ddz = getbitsglonass(&gstr[0], 85-40, 5); // 2^-30

    P = getbitu(&gstr[0], 85 - 66, 1);
    P3 = getbitu(&gstr[0], 85 - 80, 1);

    gamman = getbitu(&gstr[0], 85 - 79, 11);
  }


  /* NT is the 'day number' within the current four-year-plan, which run in blocks from 1996.
     Not yet sure if this starts from 0 or not (I guess 1)
  */
  
  uint16_t NT; 
  uint8_t FT, En, deltaTaun, M;
  uint32_t taun;
  bool P4;
  
  void parse4(std::basic_string_view<uint8_t> gstr)
  {
    NT = getbitu(&gstr[0], 85-26, 11);
    FT = getbitu(&gstr[0], 85-33, 4);
    M = getbitu(&gstr[0], 85-10, 2);
    taun = getbitsglonass(&gstr[0], 85-80, 22);
    En = getbitu(&gstr[0], 85-53, 5);
    P4 = getbitu(&gstr[0], 85-34, 1);
    // missing delta tau n
  }

  uint8_t n4; // counting from 1996 ('n4=1'), this is the 4-year plan index we are currently in
  uint16_t taugps;
  void parse5(std::basic_string_view<uint8_t> gstr)
  {
    n4=getbitu(&gstr[0], 85-36, 5);
    taugps = getbitsglonass(&gstr[0], 85-31, 22);

  }


  
};