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Minmea is a minimalistic GPS parser library written in pure C intended forresource-constrained platforms, especially microcontrollers and other embeddedsystems.

• Written in ISO C99.
• No dynamic memory allocation.
• No floating point usage in the core library.
• Supports both fixed and floating point values.
• One source file and one header - can't get any simpler.
• Tested under Linux, OS X, Windows and embedded ARM GCC.
• Easily extendable to support new sentences.
• Complete with a test suite and static analysis.

• GBS (Satellite Fault Detection)
• GGA (Fix Data)
• GLL (Geographic Position: Latitude/Longitude)
• GSA (DOP and active satellites)
• GST (Pseudorange Noise Statistics)
• GSV (Satellites in view)
• RMC (Recommended Minimum: position, velocity, time)
• VTG (Track made good and Ground speed)
• ZDA (Time & Date - UTC, day, month, year and local time zone)

Adding support for more sentences is trivial; seeminmea.c source. Good documentationon NMEA is athttps://gpsd.gitlab.io/gpsd/NMEA.html

Minmea runs out-of-the-box under most Unix-compatible systems. Support for non-Unix systems(including native Windows builds under MSVC) is provided via compatibility headers:

1. DefineMINMEA_INCLUDE_COMPAT in the build environment.
2. Add appropriate compatibility header from undercompat/ directory asminmea_compat.h.

If your GPS receiver outputs very long sentences, consider increasingMINMEA_MAX_SENTENCE_LENGTHin your build environment.

Internally, minmea stores fractional numbers as pairs of two integers:{value, scale}.For example, a value of"-123.456" would be parsed as{-123456, 1000}. As thisformat is quite unwieldy, minmea provides the following convenience functions for convertingto either fixed-point or floating-point format:

• minmea_rescale({-123456, 1000}, 10) => -1235
• minmea_float({-123456, 1000}) => -123.456

The compound typestruct minmea_float usesint_least32_t internally. Therefore,the coordinate precision is guaranteed to be at least[+-]DDDMM.MMMMM (five decimal digits)or ±2cm LSB at the equator. Note that GPS modules commonly only provide four decimal digits([+-]DDDMM.MMMM), which equates to ±20cm (0.0001 minute is 0.0001/60 degrees and one degreeis about 111km) at the equator.

NMEA uses the clunkyDDMM.MMMM format which, honestly, is not good in the internet era.Internally, minmea stores it as a fractional number (see above); for practical uses,the value should be probably converted to the DD.DDDDD floating point format using thefollowing function:

• minmea_tocoord({-375165, 100}) => -37.860832

The library doesn't perform this conversion automatically for the following reasons:

• The conversion is not reversible.
• It requires floating point support.
• The user might want to perform this conversion later on or retain the original values.

charline[MINMEA_MAX_SENTENCE_LENGTH];while (fgets(line,sizeof(line),stdin)!=NULL) {switch (minmea_sentence_id(line, false)) {caseMINMEA_SENTENCE_RMC: {structminmea_sentence_rmcframe;if (minmea_parse_rmc(&frame,line)) {printf("$RMC: raw coordinates and speed: (%d/%d,%d/%d) %d/%d\n",frame.latitude.value,frame.latitude.scale,frame.longitude.value,frame.longitude.scale,frame.speed.value,frame.speed.scale);printf("$RMC fixed-point coordinates and speed scaled to three decimal places: (%d,%d) %d\n",minmea_rescale(&frame.latitude,1000),minmea_rescale(&frame.longitude,1000),minmea_rescale(&frame.speed,1000));printf("$RMC floating point degree coordinates and speed: (%f,%f) %f\n",minmea_tocoord(&frame.latitude),minmea_tocoord(&frame.longitude),minmea_tofloat(&frame.speed));            }        }break;caseMINMEA_SENTENCE_GGA: {structminmea_sentence_ggaframe;if (minmea_parse_gga(&frame,line)) {printf("$GGA: fix quality: %d\n",frame.fix_quality);            }        }break;caseMINMEA_SENTENCE_GSV: {structminmea_sentence_gsvframe;if (minmea_parse_gsv(&frame,line)) {printf("$GSV: message %d of %d\n",frame.msg_nr,frame.total_msgs);printf("$GSV: satellites in view: %d\n",frame.total_sats);for (inti=0;i<4;i++)printf("$GSV: sat nr %d, elevation: %d, azimuth: %d, snr: %d dbm\n",frame.sats[i].nr,frame.sats[i].elevation,frame.sats[i].azimuth,frame.sats[i].snr);            }        }break;    }}

Simply addminmea.[ch] to your project,#include "minmea.h" and you'regood to go.

Building and running the tests requires the following:

• CMake
• Check Framework (https://libcheck.github.io/check/).
• Clang Static Analyzer (https://clang-analyzer.llvm.org/).

If you have both in your$PATH, running the tests should be as simple as:

mkdir buildcd buildcmake ../makemake test

It's possible to build the library without the unit tests and their dependencies.

mkdir buildcd buildcmake -DMINMEA_ENABLE_TESTING=OFF ..make

• Only a handful of frames is supported right now.
• There's no support for omitting parts of the library from building. Asa workaround, use the-ffunction-sections -Wl,--gc-sections linker flags(or equivalent) to remove the unused functions (parsers) from the final image.
• Some systems lacktimegm. On these systems, the recommended course ofaction is to build with-Dtimegm=mktime which will work correctly as longthe system runs in the defaultUTC timezone.

1. Use the GitHub pull request system.
2. Make sure to follow to existing style (naming, indentation, etc.)
3. Write unit tests for any new functionality you add.
4. Be aware you're submitting your work under the repository's license.

Minmea is open source software; seeCOPYING for amusement. Email me if thelicense bothers you and I'll happily re-license under anything else under the sun.

Minmea was written by Kosma Moczek <kosma@kosma.pl> and Patryk Szymczak<patryk.szymczak@gmail.com> at Cloud Your Car, with bugs fixed by countlessgood people.