nmea.cpp

本系统为公交车辆调度系统

#include "stdafx.h"
#include "nmea.h"

#ifdef _DEBUG
#undef THIS_FILE
static char BASED_CODE THIS_FILE[] = __FILE__;
#endif


NMEA_BOOLEAN CNmeaSentence::Boolean(int nField) const
{
  CString sField(Field(nField));

  if (sField == _T("A"))
    return True;
  else if (sField == _T("V"))
    return False;
  else
    return Unknown;
}


int CNmeaSentence::HexDigitToInt(char c)
{
  int rVal = 0;
  if ((c >= 'a') && (c <= 'f'))
    rVal =  c - 'a' + 10;
  else if ((c >= 'A') && (c <= 'F'))
    rVal =  c - 'A' + 10;
  else if ((c >= '0') && (c <= '9'))
    rVal = c - '0';

  return rVal;
}

DWORD CNmeaSentence::HexValue(const CString& sHexString)
{
  int nLen = sHexString.GetLength();
  DWORD rVal = 0;
  int nMultiplier = 1;
  for (int i=nLen-1; i>=0; i--)
  {
    TCHAR c = sHexString.GetAt(i);
    rVal += (HexDigitToInt((char)c) * nMultiplier);
    nMultiplier *= 16;
  }

  return rVal;
}

BYTE CNmeaSentence::ComputeChecksum() const
{
  BYTE checksum = 0;

  int nLength = m_Sentence.GetLength();
  int i = 1; // Skip over the $ at the begining of the CNmeaSentence

  while (i < nLength && 
         m_Sentence[i] != _T('*') && 
         m_Sentence[i] != _T('\r') && 
         m_Sentence[i] != _T('\n') )
  {
    checksum ^= (BYTE) m_Sentence[i];
    i++;
  }

  return checksum;
}

double CNmeaSentence::Double(int nField) const
{
  CString sField(Field(nField));

  double rVal = 0.0;

  #ifdef _UNICODE
    int nLength = sField.GetLength();
    int nSize = (nLength + 1)/sizeof(TCHAR);
    char* pszFieldAscii = new char[nSize];

    WideCharToMultiByte(CP_ACP, 0, sField, -1, pszFieldAscii, nSize, NULL, NULL);
    rVal = ::atof(pszFieldAscii);

    delete [] pszFieldAscii;
  #else
    rVal = ::atof(sField);
  #endif

  return rVal;
}

NMEA_EASTWEST CNmeaSentence::EastOrWest(int nField) const
{
  CString sField(Field(nField));

  if (sField == _T("E"))
    return East;
  else if (sField == _T("W"))
    return West;
  else
    return EW_Unknown;
}

NMEA_LONGITUDE CNmeaSentence::Longitude(int nPositionFieldNumber, int nEastingFieldNumber) const
{
  NMEA_LONGITUDE rVal;
  rVal.Value = Angle(nPositionFieldNumber);
  rVal.Easting = EastOrWest(nEastingFieldNumber);
  return rVal;
}

NMEA_LATITUDE CNmeaSentence::Latitude(int nPositionFieldNumber, int nNorthingFieldNumber) const
{
  NMEA_LATITUDE rVal;
  rVal.Value = Angle(nPositionFieldNumber);
  rVal.Northing = NorthOrSouth(nNorthingFieldNumber);
  return rVal;
}

CString CNmeaSentence::Field(int nDesiredField) const
{
  CString rVal;

  int i = 1;
  int nCurrentField = 0;

  int nLen = m_Sentence.GetLength();

  while (nCurrentField < nDesiredField && i < nLen)
  {
    if (m_Sentence[i] == _T(',') || m_Sentence[i] == _T('*'))
      nCurrentField++;
    i++;
  }

  if (nCurrentField == nDesiredField)
  {
    while (i < nLen &&
           m_Sentence[i] != _T(',') &&
           m_Sentence[i] != _T('*') &&
           m_Sentence[i] != _T('\n') &&
           m_Sentence[i] != _T('\r') &&
           m_Sentence[i] != 0x00 )
    {
      rVal += m_Sentence[i];
      i++;
    }
  }

  return rVal;
}

int CNmeaSentence::Integer(int nField) const
{
  CString sInteger(Field(nField));
  return ::_ttoi(sInteger);
}

NMEA_BOOLEAN CNmeaSentence::IsChecksumBad(int nField) const
{
  // Checksums are optional, return TRUE if an existing checksum is known to be bad
  CString sChecksum(Field(nField));

  if (sChecksum.IsEmpty())
    return Unknown;

  BYTE CalculatedCheckSum = ComputeChecksum();
  DWORD ReceivedCheckSum = HexValue(sChecksum);

  if (CalculatedCheckSum != ReceivedCheckSum)
    return True;
  else
    return False;
}

NMEA_NORTHSOUTH CNmeaSentence::NorthOrSouth(int nField) const
{
  CString sField(Field(nField));

  if (sField == _T("N"))
    return North;
  else if (sField == _T("S"))
    return South;
  else
    return NS_Unknown;
}

NMEA_TIME CNmeaSentence::Time(int nField) const
{
  NMEA_TIME rVal;
  ZeroMemory(&rVal, sizeof(NMEA_TIME));
  CString sTemp(Field(nField));
  if (sTemp.GetLength() >= 6)
  {
    TCHAR sNumber[3];

    sNumber[0] = sTemp[0];
    sNumber[1] = sTemp[1];
    sNumber[2] = 0x00;
    rVal.wHour = (WORD) ::_ttoi(sNumber);

    sNumber[0] = sTemp[2];
    sNumber[1] = sTemp[3];
    rVal.wMinute = (WORD) ::_ttoi(sNumber);

    sNumber[0] = sTemp[4];
    sNumber[1] = sTemp[5];
    rVal.wSecond = (WORD) ::_ttoi(sNumber);
  }

  return rVal;
}

NMEA_DATE CNmeaSentence::Date(int nField) const
{
  NMEA_DATE rVal;
  ZeroMemory(&rVal, sizeof(NMEA_DATE));
  CString sTemp(Field(nField));
  if (sTemp.GetLength() >= 6)
  {
    TCHAR sNumber[3];

    sNumber[0] = sTemp[0];
    sNumber[1] = sTemp[1];
    sNumber[2] = 0x00;
    rVal.wDay = (WORD) ::_ttoi(sNumber);

    sNumber[0] = sTemp[2];
    sNumber[1] = sTemp[3];
    rVal.wMonth = (WORD) ::_ttoi(sNumber);

    sNumber[0] = sTemp[4];
    sNumber[1] = sTemp[5];
    rVal.wYear = (WORD) ::_ttoi(sNumber);

    //intelligently adjust the year
    if (rVal.wYear < 80)
      rVal.wYear += 2000;
    else if (rVal.wYear >= 75)
      rVal.wYear += 1900;
  }

  return rVal;
}

NMEA_ANGLE CNmeaSentence::Angle(int nField) const
{
  NMEA_ANGLE rVal;
  ZeroMemory(&rVal, sizeof(NMEA_ANGLE));

  CString sTemp(Field(nField));

  int nPointIndex = sTemp.Find(_T('.'));
  if (nPointIndex != -1)
  {
    CString sUnits(sTemp.Left(nPointIndex));
    int nValue = ::_ttoi(sUnits);
    rVal.Degrees = (WORD) (nValue/100);
    rVal.Minutes = (WORD) (nValue - rVal.Degrees*100);

    CString sFraction(sTemp.Right(sTemp.GetLength() - nPointIndex));
    double fValue = 0.0;
    #ifdef _UNICODE
      int nLength = sFraction.GetLength();
      int nSize = (nLength + 1)/sizeof(TCHAR);
      char* pszFieldAscii = new char[nSize];

      WideCharToMultiByte(CP_ACP, 0, sFraction, -1, pszFieldAscii, nSize, NULL, NULL);
      fValue = ::atof(pszFieldAscii);

      delete [] pszFieldAscii;
    #else
      fValue = ::atof(sFraction);
    #endif

    rVal.Seconds = (WORD) (fValue*60);
    rVal.CentiSeconds = (WORD) ((fValue*60 - rVal.Seconds)*100.0);
  }

  return rVal;
}

DWORD CNmeaSentence::NmeaAngleToHundrethsOfSeconds(const NMEA_ANGLE& angle)
{
  DWORD rVal = angle.Degrees*360000 + 
               angle.Minutes*6000 +
               angle.Seconds*100 +
               angle.CentiSeconds;
  return rVal;
}

DWORD CNmeaSentence::NmeaBearingToHundrethsOfDegrees(const double& value)
{
  int nDigits = (int) value;
  int nHundreths = (int) ((value - nDigits)*100);
  return nDigits*100 + nHundreths;
}


CRMCResponse::CRMCResponse()
{
  Empty();
}

CRMCResponse::~CRMCResponse()
{
  Empty();
}

void CRMCResponse::Empty()
{
  ZeroMemory(&m_Time, sizeof(NMEA_TIME));
  ZeroMemory(&m_Date, sizeof(NMEA_DATE));
  m_IsDataValid              = Unknown;
  ZeroMemory(&m_Latitude, sizeof(NMEA_LATITUDE));
  ZeroMemory(&m_Longitude, sizeof(NMEA_LONGITUDE));
  m_SpeedOverGroundKnots       = 0.0;
}

BOOL CRMCResponse::Parse(const CNmeaSentence& sentence)
{
  // First we check the checksum
  NMEA_BOOLEAN check = sentence.IsChecksumBad(12);
  if (check == True)
  {
    TRACE(_T("CRMCResponse::Parse detected an Invalid checksum\n"));
    return FALSE;
  }
  else if (check == Unknown)
  {
    TRACE(_T("CRMCResponse::Parse detected a missing checksum\n"));
    return FALSE;
  } 

  //then the data
  m_Time                 = sentence.Time(1);
  m_Date                 = sentence.Date(9);
  m_IsDataValid          = sentence.Boolean(2);
  m_Latitude             = sentence.Latitude(3, 4);
  m_Longitude            = sentence.Longitude(5, 6);
  m_SpeedOverGroundKnots = sentence.Double(7);
  m_Bearing              = sentence.Double(8);

  return TRUE;
}




CGGAResponse::CGGAResponse()
{
  Empty();
}

CGGAResponse::~CGGAResponse()
{
  Empty();
}

void CGGAResponse::Empty()
{
  m_GPSQuality            = 0;
  m_nSatellites           = 0;
  m_AntennaAltitudeMeters = 0.0;
}

BOOL CGGAResponse::Parse(const CNmeaSentence& sentence)
{
  // First we check the checksum...
  if (sentence.IsChecksumBad(15) == True)
  {
    TRACE(_T("CGGAResponse::Parse detected an Invalid Checksum"));
    return FALSE;
  } 

  m_GPSQuality            = sentence.Integer(6);
  m_nSatellites           = sentence.Integer(7);
  m_AntennaAltitudeMeters = sentence.Double(9);

  return TRUE;
}