nmea.h

00001 /*
00002     File:       nmea.h
00003     Version:    0.1.0
00004     Date:       Feb. 23, 2013
00005     License:    GPL v2
00006     
00007     NMEA GPS content parser
00008     
00009     ****************************************************************************
00010     Copyright (C) 2013 Radu Motisan  <radu.motisan@gmail.com>
00011     
00012     http://www.pocketmagic.net
00013 
00014     This program is free software; you can redistribute it and/or modify
00015     it under the terms of the GNU General Public License as published by
00016     the Free Software Foundation; either version 2 of the License, or
00017     (at your option) any later version.
00018 
00019     This program is distributed in the hope that it will be useful,
00020     but WITHOUT ANY WARRANTY; without even the implied warranty of
00021     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00022     GNU General Public License for more details.
00023 
00024     You should have received a copy of the GNU General Public License
00025     along with this program; if not, write to the Free Software
00026     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
00027     ****************************************************************************
00028  */
00029 //#include "../timeout.h"
00030 
00031 
00032 
00033 class NMEA {
00034     
00035     private:
00036         bool            m_bFlagRead,                    // flag used by the parser, when a valid sentence has begun
00037                         m_bFlagDataReady;               // valid GPS fix and data available, user can call reader functions
00038         char            tmp_words[20][15],              //  hold parsed words for one given NMEA sentence
00039                         tmp_szChecksum[15];             //  hold the received checksum for one given NMEA sentence
00040         
00041         // will be set to true for characters between $ and * only
00042         bool            m_bFlagComputedCks ;            // used to compute checksum and indicate valid checksum interval (between $ and * in a given sentence)
00043         int             m_nChecksum ;                   // numeric checksum, computed for a given sentence
00044         bool            m_bFlagReceivedCks ;            // after getting  * we start cuttings the received checksum
00045         int             index_received_checksum ;       // used to parse received checksum
00046         
00047         // word cutting variables
00048         int             m_nWordIdx ,                    // the current word in a sentence
00049                         m_nPrevIdx,                     // last character index where we did a cut
00050                         m_nNowIdx ;                     // current character index
00051         
00052         // globals to store parser results
00053         float           res_fLongitude;                 // GPRMC and GPGGA
00054         char            res_clon;                       // E or W
00055         float           res_fLatitude;                  // GPRMC and GPGGA
00056         char            res_clat;                       // N or S
00057         unsigned char   res_nUTCHour, res_nUTCMin, res_nUTCSec,     // GPRMC and GPGGA 
00058                         res_nUTCDay, res_nUTCMonth, res_nUTCYear;   // GPRMC
00059         int             res_nSatellitesUsed;            // GPGGA
00060         float           res_fAltitude;                  // GPGGA
00061         float           res_fSpeed;                     // GPRMC
00062         float           res_fBearing;                   // GPRMC
00063         
00064         // the parser, currently handling GPRMC and GPGGA, but easy to add any new sentences
00065         void            parsedata();
00066         // aux functions
00067         int             digit2dec(char hexdigit);
00068         float           string2float(char* s);
00069         int             mstrcmp(const char *s1, const char *s2);
00070         float           trunc(float v);
00071         
00072     public:
00073         // constructor, initing a few variables
00074         NMEA() {
00075             m_bFlagRead = false; //are we in a sentence?
00076             m_bFlagDataReady = false; //is data available?
00077         }
00078         
00079         /*
00080          * The serial data is assembled on the fly, without using any redundant buffers. 
00081          * When a sentence is complete (one that starts with $, ending in EOL), all processing is done on 
00082          * this temporary buffer that we've built: checksum computation, extracting sentence "words" (the CSV values), 
00083          * and so on.
00084          * When a new sentence is fully assembled using the fusedata function, the code calls parsedata. 
00085          * This function in turn, splits the sentences and interprets the data. Here is part of the parser function, 
00086          * handling both the $GPRMC NMEA sentence:
00087          */
00088         int             fusedata(char c);
00089         
00090 
00091         // READER functions: retrieving results, call isdataready() first
00092         bool            isdataready();
00093         int             getHour();
00094         int             getMinute();
00095         int             getSecond();
00096         int             getDay();
00097         int             getMonth();
00098         int             getYear();
00099         float           getLatitude();
00100         char            getlatc();
00101         float           getLongitude();
00102         char            getlonc();
00103         int             getSatellites();
00104         float           getAltitude();
00105         float           getSpeed();
00106         float           getBearing();
00107     };
00108