STM32 NEO-6M

TinyGPS-style NMEA parser and interrupt-driven UART receive helper for the u-blox NEO-6M GPS module on STM32.

Features

• byte-by-byte NEO6M_Encode() parser
• decoded data stored in a single handle
• checksum-verified NMEA sentence parsing
• parsed RMC and GGA sentence support
• decoded location, date, time, speed, course, satellites, HDOP, altitude, and fix quality
• optional UART RX interrupt adapter with no main.h dependency in the public header

Parsed Data

The driver updates these values when valid NMEA data is received:

• latitude and longitude in degrees scaled by 1e7
• UTC date and time
• speed in knots scaled by 100
• course in degrees scaled by 100
• satellites count
• HDOP scaled by 100
• altitude in centimeters
• fix quality and fix state

Each field carries valid and updated flags similar to TinyGPS-style usage.

Quick Start

1. Initialize the handle with NEO6M_Init(&gps).
2. Feed incoming bytes using NEO6M_Encode(&gps, byte).
3. Read decoded fields from the handle after updated flags are set.

Minimal Parser Flow

NEO6M_HandleTypeDef gps;

NEO6M_Init(&gps);

while (have_next_byte()) {
    uint8_t ch = next_byte();
    (void)NEO6M_Encode(&gps, (char)ch);

    if (gps.location.updated != 0U) {
        int32_t lat = gps.location.latitude_deg_e7;
        int32_t lon = gps.location.longitude_deg_e7;
        NEO6M_ClearUpdates(&gps);
    }
}

Interrupt-Driven UART RX

For STM32 HAL projects, the library can own the one-byte receive buffer and re-arm reception automatically:

1. Attach a UART receive callback with NEO6M_AttachUart()
2. Start reception with NEO6M_StartReceiveIT()
3. Call NEO6M_RxCpltCallback() from HAL_UART_RxCpltCallback()

See examples/usart2_rx_it_hal.c.

USART2 Note

If you use USART2 for GPS RX:

• configure the UART for 9600 8N1
• only RX is required from the STM32 side
• on many STM32 MCUs, USART2 RX is on PA3
• verify your exact TX or alternate pin mapping in the datasheet before assuming PA4

Return Codes

• NEO6M_OK: success
• NEO6M_ERR_INVALID_ARG: invalid argument or missing callback
• NEO6M_ERR_IO: transport callback failure