nmea.h File Reference

Data Structures
struct	GPSlocation

Typedefs
typedef struct GPSlocation	loc_t

Enumerations
enum	nmea_message_type { NMEA_UNKNOWN = 0x00 , NMEA_GPRMC = 0x01 , NMEA_GPGGA = 0x02 }

Functions
nmea_message_type	nmea_get_message_type (const char *)
int	nmea_valid_checksum (const char *)
void	gps_location (loc_t *, char const *const)
static int	str2int (const char *a, const int len)

Typedef Documentation

loc_t

typedef struct GPSlocation loc_t

Definition at line 40 of file nmea.h.

Enumeration Type Documentation

nmea_message_type

enum nmea_message_type

Enumerator
NMEA_UNKNOWN
NMEA_GPRMC
NMEA_GPGGA

Definition at line 13 of file nmea.h.

             {
    NMEA_UNKNOWN = 0x00,
    NMEA_GPRMC = 0x01,
    NMEA_GPGGA = 0x02
} nmea_message_type;

Function Documentation

gps_location()

void gps_location	(	loc_t *	coord,
		char const * const	buffer
	)

Definition at line 298 of file nmea.cpp.

                                                           {
    coord->type = nmea_get_message_type(buffer);
 
    switch (coord->type) {
    case NMEA_GPGGA:
        nmea_parse_gpgga(buffer, coord);
        gps_convert_deg_to_dec(&(coord->latitude), coord->lat, &(coord->longitude), coord->lon);
        break;
    case NMEA_GPRMC:
        nmea_parse_gprmc(buffer, coord);
        break;
    case NMEA_UNKNOWN:
        // unknown message type
        break;
    }
}

Referenced by onGpsMessage().

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nmea_get_message_type()

nmea_message_type nmea_get_message_type

(

const char *

message

)

Get the message type (GPGGA, GPRMC, etc..)

This function filters out also wrong packages (invalid checksum)

Parameters

message

The NMEA message

Returns

The type of message if it is valid

Definition at line 259 of file nmea.cpp.

                                                             {
    int checksum = nmea_valid_checksum(message);
    if (checksum != _EMPTY) {
        return static_cast<nmea_message_type>(checksum);
    }
 
    if (strstr(message, NMEA_GPGGA_STR) != NULL) {
        return NMEA_GPGGA;
    }
 
    if (strstr(message, NMEA_GPRMC_STR) != NULL) {
        return NMEA_GPRMC;
    }
 
    return NMEA_UNKNOWN;
}

Referenced by gps_location().

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nmea_valid_checksum()

int nmea_valid_checksum

(

const char *

message

)

Definition at line 276 of file nmea.cpp.

                                              {
    char p;
    int sum = 0;
    const char* starPtr = strrchr(message, '*');
    if (!starPtr) {
        return NMEA_CHECKSUM_ERR;
    }
    const char* int_message = starPtr + 1;
    long checksum = hex2int(int_message, 2);
 
    ++message;
    while ((p = *message++) != '*') {
        sum ^= p;
    }
 
    if (sum != checksum) {
        return NMEA_CHECKSUM_ERR;
    }
    return _EMPTY;
}

Referenced by nmea_get_message_type().

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str2int()

static int str2int ( const char *  a, const int  len  )

static

Definition at line 48 of file nmea.h.

                                                  {
    int i = 0,  k = 0;
    while (i < len) {
        k = (k << 3) + (k << 1) + (*a) - '0';
        a++;
        i++;
    }
    return k;
}

Referenced by nmea_parse_gprmc().

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