GPS Module (NEO-6M / NEO-M8N)
Module
A complete satellite navigation receiver on a postage stamp: feed it power and sky view, and it streams your latitude, longitude, altitude, speed and atomic-clock time over serial as NMEA sentences.
What it looks like
GPS Module (NEO-6M / NEO-M8N)
A typical module — exact shape, colour and markings vary between manufacturers.
Types & variants
Key specs
Constellations
—GPS-only (NEO-6M) vs multi-GNSS (M8N+) — more satellites = faster, steadier fixes, especially between buildings.
Position accuracy
m~2.5 m CEP in open sky; worse in urban canyons. (Centimetre work needs RTK modules like ZED-F9P — a different budget.)
Time to first fix
sCold start 26–35 s typical, hot start ~1 s. The backup battery/EEPROM on the module keeps ephemeris for fast hot starts.
Update rate
Hz1 Hz default; u-blox configures to 5–10 Hz for drones/vehicles.
Interface
—UART at 9600 baud (default) streaming NMEA text; u-blox UBX binary protocol for configuration; some modules add I2C.
Antenna
—Ceramic patch (needs sky-facing orientation) or U.FL for external active antennas — the single biggest performance factor.
Markings
Module silk: VCC, GND, TX, RX (+PPS on some). A fix LED blinks once per second when locked. u-blox chip marking identifies generation (NEO-6M/M8N).
Standard values
NEO-6M GY-GPS6MV2 blue board (₹300-class), NEO-M8N with active antenna for drones, ATGM336H as the budget multi-GNSS pick. Default 9600-8-N-1 serial.
How to choose
1) M8N-or-newer for anything mobile or urban — the multi-constellation difference is real. 2) External active antenna via U.FL for dashcams/trackers inside vehicles. 3) Need timing (NTP server, frequency reference)? Pick a module exposing the PPS pin — it's accurate to tens of nanoseconds. 4) 3.3 V logic on most modules: level-shift RX if driving from a 5 V Arduino. 5) First test OUTDOORS — indoor 'it doesn't work' is usually just concrete over the antenna.
Pinout & package
NEO-6M / NEO-M8N module — UART header
Check first: RX and TX are named from the module's point of view: the module's TX goes to your MCU's RX, and vice versa. Default baud is usually 9600.
UART: VCC (3.3–5 V input via onboard regulator), GND, TX→MCU RX, RX←MCU TX, optional PPS. Libraries: TinyGPS++ (Arduino), gpsd (Linux/Pi).
Example circuits
- Vehicle tracker: NEO-6M + SIM800 GSM module texting live coordinates
- Drone flight controller with M8N + compass for position hold and return-to-home
- Stratum-1 NTP time server: Pi + GPS PPS pin disciplining the clock
- Hiking logger writing NMEA tracks to SD for mapping later
Common failures
No fix indoors (not a failure — physics), dead backup cell making every start a slow cold start, wrong TX/RX crossing (silence on serial), counterfeit u-blox chips with flaky firmware, and detached ceramic antennas after drops.
How to test
Wire TX to a USB-serial adapter and open a terminal at 9600 baud: NMEA sentences ($GPGGA/$GNGGA...) should stream immediately even without a fix. Take it outside; within a minute the GGA sentence shows satellites and coordinates, and the fix LED blinks. u-center (u-blox PC tool) visualises everything.
Substitutes
Any NMEA-speaking UART GNSS module drops in (adjust baud). Phone-grade assisted GNSS (via a companion app) substitutes for casual coordinates; RTK modules substitute when centimetres matter.