GNSS 28 Click

How does it work?

GNSS 28 Click is based on the SL871L (SL871LG3240R003000), a multi-constellation GNSS module from Telit Cinterion built around the low-power Mediatek MT3333 engine. Designed to deliver exceptional positioning accuracy, short time-to-first-fix (TTFF), and low energy consumption, this module makes GNSS 28 Click suitable for both battery-powered systems and continuous tracking applications. The SL871L supports GPS (L1), GLONASS (L1, FDMA), Galileo (E1), and BeiDou (B1) frequency bands, providing robust global coverage and high positional reliability even in challenging urban or environmental conditions. It provides precise multi-constellation satellite positioning and reliable navigation performance for embedded applications such as asset tracking, navigation systems, environmental monitoring, and location-based services.

With 99 search and 33 tracking channels, along with SBAS support for WAAS, EGNOS, MSAS, and GAGAN, it ensures improved accuracy and integrity of positioning data. Integrated AGPS functionality, capable of using both locally generated and server-based ephemeris prediction, significantly reduces TTFF for faster start-up times. The module’s additional low-noise amplifier (LNA) enhances RF sensitivity, while its DC block and jammer rejection circuitry improve signal stability and minimize interference. It supports both active and passive antennas, configurable fix reporting rates up to 10Hz, it is compliant with the standard NMEA protocol and fully compatible with Telit Cinterion NMEA commands, and includes low-power periodic and GNSS low-power (GLP) operating modes to optimize energy efficiency.

The GNSS 28 Click communicates with the host MCU through a UART interface using the standard UART RX and TX pins. The default communication speed is set at 115200bps, ensuring efficient data exchange. It also provides an I2C interface for communication with a host MCU. Still, it must be noted that I2C interface can only be operated in the peripheral mode. In addition to its standard power supply configuration, GNSS 27 Click incorporates a dedicated backup power circuit that enables standalone operation and data retention. A coin-cell battery mounted on the back side of the board provides continuous power to the module’s internal real-time clock (RTC) and memory, allowing it to preserve essential timing, configuration, and satellite ephemeris data even when the main supply is disconnected.

Alongside its primary communication interface pins, GNSS 28 Click uses several additional control and monitoring pins that enhance module management and operational reliability. The RST pin is used to perform a hardware reset of the module, and a blue PPS LED indicator, which, in combination with the PPS pin, detects a synchronized pulse signal from the SL871LG3240R003000 once per second. The AOP pin (Antenna Open) serve as output for a special NMEA message from receiver indicating the antenna line is open, and the FON pin provides control over the module’s power state, enabling it to enter a backup or low-power mode to minimize energy consumption during idle periods.

In addition, the board features one test point ASH (Antenna Shorted) serve as antenna status indicator. This signal allow the system to detect abnormal antenna conditions: ASH indicating excessive antenna current (short-circuit). The board also features one SMA connector for GNSS antenna that MIKROE offers, like the Active GPS Antenna for flexible and efficient connectivity options.

This Click board™ can be operated only with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. It also comes equipped with a library containing functions and example code that can be used as a reference for further development.

Specifications

Pinout diagram

This table shows how the pinout on GNSS 28 Click corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).

Notes	Pin					Pin	Notes
Antenna Open	AOP	1	AN	PWM	16	FON	Force Full-Power Mode
Reset	RST	2	RST	INT	15	PPS	Timepulse Indicator
ID COMM	CS	3	CS	RX	14	TX	UART TX
	NC	4	SCK	TX	13	RX	UART RX
	NC	5	MISO	SCL	12	SCL	I2C Clock
	NC	6	MOSI	SDA	11	SDA	I2C Data
Power Supply	3.3V	7	3.3V	5V	10	NC
Ground	GND	8	GND	GND	9	GND	Ground

Onboard settings and indicators

GNSS 28 Click electrical specifications

Software Support

GNSS 28 Click demo application is developed using the NECTO Studio, ensuring compatibility with mikroSDK's open-source libraries and tools. Designed for plug-and-play implementation and testing, the demo is fully compatible with all development, starter, and mikromedia boards featuring a mikroBUS™ socket.

Example Description

This example demonstrates the use of GNSS 28 Click by reading and displaying the GNSS coordinates.

Key Functions

• gnss28_cfg_setup This function initializes Click configuration structure to initial values.
• gnss28_init This function initializes all necessary pins and peripherals used for this Click board.
• gnss28_generic_read This function reads a desired number of data bytes by using the selected serial interface.
• gnss28_parse_gga This function parses the GGA data from the read response buffer.
• gnss28_get_pps_pin This function returns the pulse per second (PPS) pin logic state.

Application Init

Initializes the driver and logger.

Application Task

Reads the received data, parses the NMEA GGA info from it, and once it receives the position fix it will start displaying the coordinates on the USB UART.

Application Output

This Click board can be interfaced and monitored in two ways:

• Application Output - Use the "Application Output" window in Debug mode for real-time data monitoring. Set it up properly by following this tutorial.
• UART Terminal - Monitor data via the UART Terminal using a USB to UART converter. For detailed instructions, check out this tutorial.

Additional Notes and Information

The complete application code and a ready-to-use project are available through the NECTO Studio Package Manager for direct installation in the NECTO Studio. The application code can also be found on the MIKROE GitHub account.