nmea.c

Construct NMEA packet in GPS module

 *        054.7,T      True track made good
 *        034.4,M      Magnetic track made good
 *        005.5,N      Ground speed, knots
 *        010.2,K      Ground speed, Kilometers per hour
 *
 * Note that, as of the 2.3 release of NMEA, there is a new field in
 * the VTG sentence at the end just prior to the checksum. For more
 * information on this field see here.
 *
 * Receivers that don't have a magnetic deviation (variation) table
 * built in will null out the Magnetic track made good.
 *
 * 
 *
 * $GPVTG
 * Track Made Good and Ground Speed. 
 *
 * eg1. $GPVTG,360.0,T,348.7,M,000.0,N,000.0,K*43
 * eg2. $GPVTG,054.7,T,034.4,M,005.5,N,010.2,K*41
 *
 *           054.7,T      True course made good over ground, degrees
 *           034.4,M      Magnetic course made good over ground, degrees
 *           005.5,N      Ground speed, N=Knots
 *           010.2,K      Ground speed, K=Kilometers per hour
 *
 * eg3. for NMEA 0183 version 3.00 active the Mode indicator field
 *      is added at the end
 *      $GPVTG,054.7,T,034.4,M,005.5,N,010.2,K,A*53
 *           A            Mode indicator (A=Autonomous, D=Differential,
 *                        E=Estimated, N=Data not valid)
 *
 *
 *
 **/

NMEA_STATUS
NMEASendGPVTG (void)
{

  NMEA_VTG_DATA NmeaVTGData;
  char pFieldBuffer[MAX_NMEA_FIELD];
  int TXBufferIndex = 0;
  char TransmitBuffer[MAX_NMEA_BUFFER];


  memset (TransmitBuffer, 0, MAX_NMEA_BUFFER);
  memset (&NmeaVTGData, 0, sizeof (NMEA_VTG_DATA));

  /**
   * Get the necessary data from the FW.
   **/
  NMEAGetGPVTGData (&NmeaVTGData);

  TXBufferIndex = 0;

  /**
   * Add the header
   **/
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_START);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_GPVTG);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);

  /**
   * True heading
   **/
  ftoa (NmeaVTGData.TrueHeading, pFieldBuffer);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, pFieldBuffer);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_TRUE_HEADING);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);

  /**
   * Mag heading
   **/
  ftoa (NmeaVTGData.MagHeading, pFieldBuffer);
  /*  NMEAAddField( TransmitBuffer, &TXBufferIndex, pFieldBuffer ); */
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_MAG_HEADING);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);


  /**
   * Ground speed knots
   **/
  ftoa (NmeaVTGData.GroundSpeedKnots, pFieldBuffer);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, pFieldBuffer);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_KNOTS);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);

  /**
   * Ground speed kilos
   **/
  ftoa (NmeaVTGData.GroundSpeedKilos, pFieldBuffer);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, pFieldBuffer);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_KILOS);
  /* NMEAAddField( TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA ); */

  /**
   * Check Sum 
   **/
  NMEAAddCheckSum (TransmitBuffer, &TXBufferIndex);

  /**
   * CR/LF
   **/
  NMEAAddCRLF (TransmitBuffer, &TXBufferIndex);

  /**
   * Now send the sentence.
   **/
  if (!ComPortWrite ((unsigned char *) &TransmitBuffer[0], TXBufferIndex))
    {
      return NMEA_FAILED;
    }

  return NMEA_SUCCESS;
}

NMEA_STATUS
NMEAGetGPRMCData (pNMEA_RMC_DATA pNmeaRMCData)
{
  DMY Dmy;
  unsigned long DateOfFix;
  /**
   * Need to convert from degrees to degrees and minutes format.
   **/
  pNmeaRMCData->TimeOfFixUTC = GetTimeOfFixUTC ();

  pNmeaRMCData->Status = NMEA_ACTIVE;   /* Cliff TODO */

  pNmeaRMCData->Lat =
    ConvertLatLonFromDegreestoDegreesMinutes (GetLatitudeAbs ());

  pNmeaRMCData->NorthSouth = GetNorthSouth ();

  pNmeaRMCData->Long =
    ConvertLatLonFromDegreestoDegreesMinutes (GetLongitudeAbs ());
  pNmeaRMCData->EastWest = GetEastWest ();


  pNmeaRMCData->GroundSpeedKnots = GetGroundSpeedKnots ();
  pNmeaRMCData->TrueHeading = GetTrueHeading ();
  GetDayMonthYear (&Dmy);

  DateOfFix =
    ((unsigned long) Dmy.Day * 10000) + ((unsigned long) Dmy.Month * 100) +
    ((unsigned long) Dmy.Year - 2000);
  pNmeaRMCData->DateOfFix = DateOfFix;

  return NMEA_SUCCESS;
}

/**
 * RMC - NMEA has its own version of essential gps pvt (position,
 * velocity, time) data. It is called RMC, The Recommended Minimum,
 * which will look similar to:
 *
 * $GPRMC,123519,A,4807.038,N,01131.000,E,022.4,084.4,230394,003.1,W*6A
 *
 * Where:
 *     RMC          Recommended Minimum sentence C
 *     123519       Fix taken at 12:35:19 UTC
 *     A            Status A=active or V=Void. Not sure what is means??? TODO
 *     4807.038,N   Latitude 48 deg 07.038' N
 *     01131.000,E  Longitude 11 deg 31.000' E
 *     022.4        Speed over the ground in knots
 *     084.4        Track angle in degrees True
 *     
 *  TODO Why do they have a different DMY format from the one that is in ZDA?? 
 *  
 *  230394       Date - 23rd of March 1994
 *     003.1,W      Magnetic Variation
 *     *6A          The checksum data, always begins with *
 *
 * Note that, as of the 2.3 release of NMEA, there is a new field in
 * the RMC sentence at the end just prior to the checksum. For more
 * information on this field see here.
 *
 **/

NMEA_STATUS
NMEASendGPRMC (void)
{

  NMEA_RMC_DATA NmeaRMCData;
  char pFieldBuffer[MAX_NMEA_FIELD];
  int TXBufferIndex = 0;
  char TransmitBuffer[MAX_NMEA_BUFFER];


  memset (TransmitBuffer, 0, MAX_NMEA_BUFFER);
  memset (&NmeaRMCData, 0, sizeof (NMEA_RMC_DATA));

  /**
   * Get the necessary data from the FW.
   **/
  NMEAGetGPRMCData (&NmeaRMCData);

  TXBufferIndex = 0;

  /**
   * Add the header
   **/
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_START);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_GPRMC);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);


  /**
   * Field 0 Time   
   *
   * The time field must be 6 digits long. If the hour is less than 10 you 
   * must pad it with an extra zero.
   **/
  sprintf (pFieldBuffer, "%06ld.00", (long) NmeaRMCData.TimeOfFixUTC);
  /* ftod( NmeaRMCData.TimeOfFixUTC, pFieldBuffer  ); */
  NMEAAddField (TransmitBuffer, &TXBufferIndex, pFieldBuffer);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);

  /**
   * Active or Void
   **/
  if (NmeaRMCData.Status == NMEA_ACTIVE)
    {
      NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_ACTIVE_STR);
      NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);
    }
  else
    {
      NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_VOID_STR);
      NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);
    }

  /**
   * Field 1 Latitude
   **/
  ftod4 (NmeaRMCData.Lat, pFieldBuffer);        /* 4 decimal places */
  NMEAAddField (TransmitBuffer, &TXBufferIndex, pFieldBuffer);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);

  /**
   * Field 2 North/South 
   **/
  if (NmeaRMCData.NorthSouth == NMEA_SOUTH)
    {
      NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_SOUTH);
    }
  else
    {
      NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_NORTH);
    }

  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);

  /**
   * Field 3 Longitude
   **/
  ftod4 (NmeaRMCData.Long, pFieldBuffer);       /* 4 decimal places */
  NMEAAddField (TransmitBuffer, &TXBufferIndex, pFieldBuffer);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);


  /**
   * Field 4 East/West
   **/
  if (NmeaRMCData.EastWest == NMEA_WEST)
    {
      NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_WEST);
    }
  else
    {
      NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_EAST);
    }

  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);



  /**
   * Speed over the ground in knots.
   **/
  ftodPrecision1 (NmeaRMCData.GroundSpeedKnots, pFieldBuffer);
  /*ftod( NmeaRMCData.GroundSpeedKnots, pFieldBuffer ); */
  NMEAAddField (TransmitBuffer, &TXBufferIndex, pFieldBuffer);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);

  /**
   * True heading
   **/
  ftodPrecision1 (NmeaRMCData.TrueHeading, pFieldBuffer);
  /* ftod( NmeaRMCData.TrueHeading, pFieldBuffer ); */
  NMEAAddField (TransmitBuffer, &TXBufferIndex, pFieldBuffer);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);

  /**
   * Date
   **/
  /* itoa (NmeaRMCData.DateOfFix, pFieldBuffer, 10); */
  sprintf (pFieldBuffer, "%ld", NmeaRMCData.DateOfFix);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, pFieldBuffer);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);

  /**
   * MagVar
   **/
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);



  /**
   * Check Sum 
   **/
  NMEAAddCheckSum (TransmitBuffer, &TXBufferIndex);

  /**
   * CR/LF
   **/
  NMEAAddCRLF (TransmitBuffer, &TXBufferIndex);

  /**
   * Now send the sentence.
   **/
  if (!ComPortWrite ((unsigned char *) &TransmitBuffer[0], TXBufferIndex))
    {
      return NMEA_FAILED;
    }

  return NMEA_SUCCESS;
}

NMEA_STATUS
NMEAGetGPZDAData (pNMEA_ZDA_DATA pNmeaZDAData)
{
  DMY Dmy;

  pNmeaZDAData->HrMinSecUTC = GetHrMinSecUTC ();
  GetDayMonthYear (&Dmy);

  pNmeaZDAData->Day = Dmy.Day;
  pNmeaZDAData->Month = Dmy.Month;
  pNmeaZDAData->Year = Dmy.Year;
  pNmeaZDAData->LocalTimeZoneHr = 8;    /* TODO */
  pNmeaZDAData->LocalTimeZoneMin = 19;

  return NMEA_SUCCESS;
}


/**
 * ZDA - Data and Time 
 *
 * $GPZDA,hhmmss.ss,dd,mm,yyyy,xx,yy*CC
 * $GPZDA,201530.00,04,07,2002,00,00*6E
 *
 * where:
 * hhmmss    HrMinSec(UTC)
 *  dd,mm,yyy Day,Month,Year
 *  xx        local zone hours -13..13
 *  yy        local zone minutes 0..59
 *  *CC       checksum
 *
 **/

NMEA_STATUS
NMEASendGPZDA (void)
{

  NMEA_ZDA_DATA NmeaZDAData;
  char pFieldBuffer[MAX_NMEA_FIELD];
  int TXBufferIndex = 0;
  char TransmitBuffer[MAX_NMEA_BUFFER];


  memset (TransmitBuffer, 0, MAX_NMEA_BUFFER);
  memset (&NmeaZDAData, 0, sizeof (NMEA_ZDA_DATA));

  /**
   * Get the necessary data from the FW.
   **/
  NMEAGetGPZDAData (&NmeaZDAData);

  TXBufferIndex = 0;

  /**
   * Add the header
   **/
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_START);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_GPZDA);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);

  /**
   * Time   
   *
   * The time field must be 6 digits long. If the hour is less than 10 you 
   * must pad it with an extra zero.
   **/
  sprintf (pFieldBuffer, "%06ld.00", (long) NmeaZDAData.HrMinSecUTC);
  /* ftod( NmeaZDAData.HrMinSecUTC, pFieldBuffer  ); */
  NMEAAddField (TransmitBuffer, &TXBufferIndex, pFieldBuffer);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);

  /**
   * Day  
   **/
  sprintf (pFieldBuffer, "%02d", NmeaZDAData.Day);
  /*itoa( NmeaZDAData.Day, pFieldBuffer, 10  ); */
  NMEAAddField (TransmitBuffer, &TXBufferIndex, pFieldBuffer);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);

  /**
   * Month   
   **/
  sprintf (pFieldBuffer, "%02d", NmeaZDAData.Month);
  /* itoa( NmeaZDAData.Month, pFieldBuffer, 10 ); */
  NMEAAddField (TransmitBuffer, &TXBufferIndex, pFieldBuffer);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);

  /**
   * Year 
   **/
  sprintf (pFieldBuffer, "%d", NmeaZDAData.Year);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, pFieldBuffer);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);


  /**
   * Local time offset hour from UTC 
   **/
  sprintf (pFieldBuffer, "%02d", NmeaZDAData.LocalTimeZoneHr);
  /*itoa( NmeaZDAData.LocalTimeZoneHr, pFieldBuffer, 10  ); */
  NMEAAddField (TransmitBuffer, &TXBufferIndex, pFieldBuffer);
  NMEAAddField (TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA);


  /**
   * Local time offset minute from UTC  
   **/
  sprintf (pFieldBuffer, "%02d", NmeaZDAData.LocalTimeZoneMin);
  /* itoa( NmeaZDAData.LocalTimeZoneMin, pFieldBuffer, 10  ); */
  NMEAAddField (TransmitBuffer, &TXBufferIndex, pFieldBuffer);
  /* NMEAAddField( TransmitBuffer, &TXBufferIndex, NMEA_SENTENCE_COMMA ); */

  /**
   * Check Sum 
   **/
  NMEAAddCheckSum (TransmitBuffer, &TXBufferIndex);

  /**
   * CR/LF
   **/
  NMEAAddCRLF (TransmitBuffer, &TXBufferIndex);

  /**
   * Now send the sentence.
   **/
  if (!ComPortWrite ((unsigned char *) &TransmitBuffer[0], TXBufferIndex))
    {
      return NMEA_FAILED;
    }

  return NMEA_SUCCESS;
}

void
ftoaPrecision0 (float value, char *strFloat)
{
  sprintf (strFloat, "%.0f", value);
}


void
ftoa (float value, char *strFloat)
{
  sprintf (strFloat, "%.2f", value);
}

void
ftod (double value, char *strDouble)
{
  sprintf (strDouble, "%.2f", value);
}

void
ftodPrecision1 (double value, char *strDouble)
{
  sprintf (strDouble, "%.1f", value);
}

void
ftod4 (double value, char *strDouble)
{
  sprintf (strDouble, "%.4f", value);   /* added two more decimal places */
}