GPS libraries¶

NMEA · UBX · LOCATIONPROVIDER · TIME SYNCHRONISATION

For positioning, MeshCore uses two libraries that serve the same purpose but have nothing in common. One parses lines of text that virtually every GPS receiver emits; the other speaks a binary protocol with one specific manufacturer.

[!NOTE] Source. This page was verified against the firmware itself: MeshCore v1.16.0, commit 03b6ef4, 28 July 2026 — files platformio.ini, src/helpers/sensors/MicroNMEALocationProvider.h and src/helpers/sensors/EnvironmentSensorManager.cpp.

How MeshCore calls this group¶

Both libraries sit behind the same abstraction, LocationProvider. The SensorManager supplies one on request:

src/helpers/SensorManager.h r.25

  virtual LocationProvider* getLocationProvider() { return NULL; }

Whoever wants a position — for the location in an advert, for telemetry or for setting the clock — asks the provider for it and does not have to know which receiver sits underneath.

stevemarple/MicroNMEA¶

NMEA 0183 is the protocol virtually every GPS receiver emits over a serial line: lines of text starting with $GP or $GN, carrying position, time, speed and the number of visible satellites, closed off with a checksum. MicroNMEA parses those lines character by character, without allocating buffers and without dynamic memory — written for microcontrollers where that matters.

MeshCore uses it in MicroNMEALocationProvider:

src/helpers/sensors/MicroNMEALocationProvider.h r.3-6

#include "LocationProvider.h"
#include <MicroNMEA.h>
#include <RTClib.h>
#include <helpers/RefCountedDigitalPin.h>

That RTClib.h sits beside it is no accident: the time from the NMEA lines is used to set the node's clock.

With twenty variants, MicroNMEA is the most common sensor library in the repo. It is also in [sensor_base], behind the ENV_INCLUDE_GPS flag.

sparkfun/SparkFun u-blox GNSS Arduino Library¶

Besides NMEA, u-blox receivers speak UBX, their own binary protocol. That is more compact, supplies more fields and allows the receiver to be configured — measurement rate, power management, which satellite systems are used. It also works over I²C, where NMEA usually runs over a serial port.

MeshCore uses that for the RAK12500, a u-blox module on the I²C bus:

src/helpers/sensors/EnvironmentSensorManager.cpp r.171-175

#ifndef TELEM_RAK12500_ADDRESS
#define TELEM_RAK12500_ADDRESS   0x42     //RAK12500 Ublox GPS via i2c
#endif
#include <SparkFun_u-blox_GNSS_Arduino_Library.h>
static SFE_UBLOX_GNSS ublox_GNSS;

Below that sits RAK12500LocationProvider, which implements the same LocationProvider interface as the NMEA version. Six variants declare the library, all of them RAK boards or derived from them.

Overview¶

Library	Version	Variants	Protocol	Bus
`stevemarple/MicroNMEA`	`^2.0.6` · `~2.0.6`	20	NMEA 0183	serial
`sparkfun/SparkFun u-blox GNSS Arduino Library`	`^2.2.27`	6	UBX	I²C

Sources¶

Translated from Dutch by Anthropic Claude