C library for parsing NMEA-0183 sentences on embedded systems. Zero heap allocation, multi-instance contexts, compile-time module selection to minimize binary size.

Use this if you need to: parse GPS/GNSS, AIS, radar, navigation, or sensor data from NMEA-0183 devices on microcontrollers or resource-constrained systems.

Don't use this if: you need NMEA-2000, need dynamic configuration, or want automatic sentence type detection without compile-time configuration.

#include "nmea.h"

// 1. Create context and config
nmea_context_t ctx;
nmea_config_t config = {
    .enabled_modules = (1 << NMEA_MODULE_GNSS) | (1 << NMEA_MODULE_SENSOR),
    .error_callback = NULL,
    .validate_checksums = true
};

// 2. Initialize
if (nmea_init(&ctx, &config) != NMEA_OK) {
    return -1;
}

// 3. Parse sentence (requires working buffer)
const char *sentence = "$GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47\r\n";
char buffer[128];  // Min 82 bytes required

if (nmea_parse(&ctx, sentence, strlen(sentence), buffer, sizeof(buffer)) == NMEA_OK) {
    // 4. Access parsed data
    nmea_gnss_state_t gnss;
    if (nmea_get_gnss_data(&ctx, &gnss) == NMEA_OK) {
        printf("Lat: %.6f, Lon: %.6f\n", gnss.latitude.degrees, gnss.longitude.degrees);
    }
}

// 5. Cleanup when done
nmea_cleanup(&ctx);

Working examples demonstrating common integration scenarios:

Basic GPS tracking: position, speed, altitude, time.

• Data: Latitude, longitude, altitude, speed, course, UTC time/date, fix quality
• Memory: ~200 bytes RAM, ~6 KB flash
• Complexity: Beginner

nmea_parse(&ctx, sentence, len, buffer, buf_size);
nmea_gnss_state_t gps;
nmea_get_gnss_data(&ctx, &gps);
printf("Position: %.6f, %.6f\n", gps.latitude.degrees, gps.longitude.degrees);

Legacy marine equipment integration: depth sounders, wind instruments, compass, speed logs, temperature sensors.

• Data: Water depth, wind speed/direction, heading, speed through water, ROT, water temperature
• Memory: ~600 bytes RAM, ~15 KB flash
• Complexity: Intermediate

nmea_sensor_state_t sensors;
nmea_get_sensor_data(&ctx, &sensors);
printf("Depth: %.1f m, Wind: %.1f knots\n",
       sensors.depth_below_transducer_meters,
       sensors.wind_speed_knots);

UART/serial port integration for Linux/POSIX systems. Includes buffering, error recovery, and statistics.

• Complexity: Intermediate

Multiple independent parser contexts for redundant GPS systems or separate data streams.

• Complexity: Intermediate

Memory optimization for resource-constrained microcontrollers.

• Complexity: Intermediate

Error handling with callbacks, statistics, recovery strategies, and health monitoring.

• Complexity: Advanced

All examples include:

• Complete, buildable code
• Detailed documentation
• Real-world use cases
• Platform-specific notes

See examples/ for complete list and doc/ for integration guides.

mkdir build && cd build
cmake ..
make
make install  # Installs to system or CMAKE_INSTALL_PREFIX

Link against libnmea.a and include nmea.h.

Modules and sentences can be disabled at compile-time in inc/nmea_config.h:

// Disable entire modules
#define NMEA_MODULE_AIS_ENABLED 0
#define NMEA_MODULE_RADAR_ENABLED 0

// Disable specific sentences
#define NMEA_SENTENCE_GGA_ENABLED 1  // Keep GPS position
#define NMEA_SENTENCE_RMC_ENABLED 1  // Keep recommended minimum
#define NMEA_SENTENCE_GSV_ENABLED 0  // Don't need satellites in view

See inc/nmea_config.h for all configuration options.

Each module groups related sentence types:

• GNSS - GPS/GLONASS/Galileo position, velocity, time, satellites (GGA, RMC, GLL, GSA, GSV, etc.)
• AIS - Automatic Identification System messages (VDM, VDO, ABM, BBM)
• Navigation - Cross-track error, waypoint arrival, bearing/distance to waypoint (APB, BOD, BWC, RMB, etc.)
• Heading - True/magnetic heading, attitude, rate of turn (HDT, HDG, ROT, etc.)
• Sensor - Depth, water temperature, wind, pressure (DBT, DPT, MTW, MWV, etc.)
• Radar - Radar status and targets (TTM, TLL, etc.)
• Safety - Alarms and safety-related messages (ALA, ALR, etc.)
• Comm - Communication state and DSC (DSC, DSE, etc.)
• System - System state and text messages (TXT, VER, etc.)
• Attitude - Pitch, roll, heave (HMR, HSS, etc.)
• Waypoint - Waypoint/route management (WPL, RTE, etc.)
• Misc - Everything else

Core functions:

• nmea_init(ctx, config) - Initialize parser context
• nmea_parse(ctx, sentence, len, buffer, buf_size) - Parse one sentence
• nmea_cleanup(ctx) - Reset context
• nmea_get_gnss_data(ctx, out) - Retrieve parsed GNSS data
• nmea_get_ais_data(ctx, out) - Retrieve parsed AIS data
• (similar accessors for other modules)

See inc/nmea.h for full API documentation.

cd build
ctest

Unit tests are in test/unit/, built with Google Test.

Context size depends on enabled modules. Typical configurations:

• GNSS only: ~200 bytes
• GNSS + Sensor: ~300 bytes
• All modules: ~1-2 KB

Use nmea_get_context_size() to query actual size for your configuration.

Buffer requirement: 82 bytes minimum for working buffer (use nmea_get_required_buffer_size()).

All functions return nmea_result_t:

nmea_result_t result = nmea_parse(&ctx, sentence, len, buf, buf_size);
if (result != NMEA_OK) {
    printf("Error: %s\n", nmea_get_error_string(result));
}

Optional error callback for real-time notification:

void my_error_handler(nmea_error_type_t type, nmea_result_t code,
                      const char *message, void *user_data) {
    fprintf(stderr, "NMEA error: %s\n", message ? message : nmea_get_error_string(code));
}

nmea_config_t config = {
    .error_callback = my_error_handler,
    .error_callback_user_data = NULL,
    // ...
};

Complete guides and references in the doc/ directory:

Getting Started:

• Integration Guide - Step-by-step setup for CMake, Makefile, Arduino, PlatformIO
• Serial Port Integration - UART/serial connection examples (STM32, ESP32, Linux, Arduino)
• FAQ - Common questions and troubleshooting

Advanced Topics:

• Stream Parsing - Buffering strategies for continuous data
• Memory Optimization - Minimize RAM/flash usage
• Error Handling - Error recovery patterns

Reference:

• Supported Sentences - Complete list of 100+ sentence types
• Documentation Index - Browse all documentation

Examples:

• GPS Tracker - Simple GPS position tracking
• Marine Instruments - Depth, wind, compass, temperature
• Serial Stream - Real serial port integration
• Multi-Instance - Multiple GPS devices
• Minimal Memory - Memory optimization
• Error Handling - Error handling patterns
• All Examples - Browse all examples

MIT License - See LICENSE

• Documentation: doc/ and examples/
• Issues: https://github.com/FinOrr/embedded-nmea-0183/issues
• Questions: Check FAQ first