11.3. `nmea` — NMEA encoding and decoding¶

Source code: src/encode/nmea.h, src/encode/nmea.c

Test code: tst/encode/nmea/main.c

Test coverage: src/encode/nmea.c

Defines

NMEA_SENTENCE_SIZE_MAX¶

NMEA_KNOTS_TO_METERS_PER_SECOND(knots)¶

Enums

enum nmea_sentence_type_t¶

Sentence types.

Values:

nmea_sentence_type_raw_t = 0¶

nmea_sentence_type_gga_t¶

nmea_sentence_type_gll_t¶

nmea_sentence_type_gsa_t¶

nmea_sentence_type_gsv_t¶

nmea_sentence_type_rmc_t¶

nmea_sentence_type_vtg_t¶

nmea_sentence_type_max_t¶

Functions

ssize_t nmea_encode(char *dst_p, struct nmea_sentence_t *src_p, size_t size)¶

Encode given NMEA sentence into given buffer.

Return

Number of bytes in the encoded string, not including the null-termination, or negative error code.

Parameters

dst_p: Null-terminated encoded sentence.
src_p: Sentence to encode.
size: Size of the destination buffer dst_p.

ssize_t nmea_decode(struct nmea_sentence_t *dst_p, char *src_p, size_t size)¶

Decode given NMEA sentence into given struct.

Return

zero(0) or negative error code.

Parameters

dst_p: Decoded NMEA sentence.
src_p: Sentence to decode, starting with a dollar sign and ending with <CR><LF>. This string is modified by this function and the decoded sentence has references to it.
size: Number of bytes in the sentence to decode, not including the null-termination.

int nmea_decode_fix_time(char *src_p, int *hour_p, int *minute_p, int *second_p)¶

Decode given NMEA fix time hhmmss. The output variables have not been modified if the decoding failed.

Return

zero(0) or negative error code.

Parameters

src_p: Fix time to decode.
hour_p: Decoded hour.
minute_p: Decoded minute.
second_p: Decoded second.

int nmea_decode_date(char *src_p, int *year_p, int *month_p, int *date_p)¶

Decode given NMEA date ddmmyy. The output variables have not been modified if the decoding failed.

Return

zero(0) or negative error code.

Parameters

src_p: Date to decode.
year_p: Decoded year.
month_p: Decoded month.
date_p: Decoded date.

int nmea_decode_position(struct nmea_position_t *src_p, long *degrees_p)¶

Decode given NMEA position angle d{2,3}mm.m+ and direction [NSEW], for example 4703.324 N, which is decoded as 47 degrees, 3.324 minutes, or 47055400 microdegrees.

The output variable has not been modified if the decoding failed.

Return

zero(0) or negative error code.

Parameters

src_p: Position to decode.
degrees_p: Decoded position in microdegrees (millions of degrees).

struct nmea_position_t¶

Public Members

char *angle_p¶

char *direction_p¶

struct nmea_value_t¶

Public Members

char *value_p¶

char *unit_p¶

struct nmea_track_made_good_t¶

Public Members

char *value_p¶

char *relative_to_p¶

struct nmea_sentence_raw_t¶

#include <nmea.h>

Raw string data.

Public Members

char *str_p¶

struct nmea_sentence_gga_t¶

#include <nmea.h>

Fix information.

Public Members

char *time_of_fix_p¶

struct nmea_position_t latitude¶

struct nmea_position_t longitude¶

char *fix_quality_p¶

char *number_of_tracked_satellites_p¶

char *horizontal_dilution_of_position_p¶

struct nmea_value_t altitude¶

struct nmea_value_t height_of_geoid¶

struct nmea_sentence_gll_t¶

#include <nmea.h>

Latitude and longitude data.

Public Members

char *time_of_fix_p¶

struct nmea_position_t latitude¶

struct nmea_position_t longitude¶

char *data_active_p¶

struct nmea_sentence_gsa_t¶

#include <nmea.h>

Overall satellite data.

Public Members

char *selection_p¶

char *fix_p¶

char *prns[12]¶

char *pdop_p¶

char *hdop_p¶

char *vdop_p¶

struct nmea_sentence_gsv_t¶

#include <nmea.h>

Detailed satellite data.

Public Members

char *number_of_sentences_p¶

char *sentence_p¶

char *number_of_satellites_p¶

char *prn_p¶

char *elevation_p¶

char *azimuth_p¶

char *snr_p¶

struct nmea_sentence_gsv_t::@45 nmea_sentence_gsv_t::satellites[4]

struct nmea_sentence_rmc_t¶

#include <nmea.h>

Recommended minimum data for GPS.

Public Members

char *time_of_fix_p¶

char *status_p¶

struct nmea_position_t latitude¶

struct nmea_position_t longitude¶

char *speed_knots_p¶

char *track_angle_p¶

char *date_p¶

struct nmea_position_t magnetic_variation¶

struct nmea_sentence_vtg_t¶

#include <nmea.h>

Track made good and speed over ground.

Public Members

struct nmea_track_made_good_t track_made_good_true¶

struct nmea_track_made_good_t track_made_good_magnetic¶

struct nmea_value_t ground_speed_knots¶

struct nmea_value_t ground_speed_kmph¶

struct nmea_sentence_t¶

#include <nmea.h>

A union of all sentences.

Public Members

nmea_sentence_type_t type¶

struct nmea_sentence_raw_t raw¶

struct nmea_sentence_gga_t gga¶

struct nmea_sentence_gll_t gll¶

struct nmea_sentence_gsa_t gsa¶

struct nmea_sentence_gsv_t gsv¶

struct nmea_sentence_rmc_t rmc¶

struct nmea_sentence_vtg_t vtg¶

union nmea_sentence_t::@46 nmea_sentence_t::@47

11.3. nmea — NMEA encoding and decoding¶

11.3. `nmea` — NMEA encoding and decoding¶