MicroMod GNSS Function Board - NEO-M9N Hookup Guide

Contributors: bboyho, Elias The Sparkiest

Hardware Overview

We've taken the u-blox NEO-M9N and broken the board out to a MicroMod Function Board! In this section, we will go over the main features of the Function Board.

For a detailed overview of the module, these integrated systems and how to use them, refer to the datasheet and integration manual linked in the Resources and Going Further.

Power

To power the board, you will need to apply power to a SparkFun Main Board. Power applied from the M.2 connector VCC line will be regulated down with the 3.3V/600mA AP2112K voltage regulator.

Communication Ports

The NEO-M9N has four communication ports. You can read NMEA data over I²C while you send configuration commands over the UART and vice/versa. The only limit is that the SPI pins are mapped onto the I²C and UART pins so it’s either SPI or I2C+UART. You will need select the port with the BUS SELECT jumper. The USB port is available at all times. There is a bilateral switch between the M.2 connector and the NEO-M9N's Serial, SPI, and I²C ports. The switch connects the appropriate port depending on the on the jumper position.

USB

The USB C connector is available for those that are interested in using the u-center software on a computer. There is a TVS diode between the USB port and NEO-M9N's USB data pins for protection.

I²C (a.k.a DDC)

The u-blox NEO-M9N has a “DDC” port which is really just an I²C port (without all the fuss of trademark issues). These pins are shared with the SPI pins. Connecting the DSEL pin to the Serial/I2C with the 2-pin jumper disables the SPI data bus while keeping the UART and I²C interface available.

UART/Serial

The classic serial pins are available on the NEO-M9N but are shared with the SPI pins. Connecting the DSEL pin to the Serial/I2C with the 2-pin jumper disables the SPI data bus while keeping the UART and I²C interface available.

• TXO/SDO = TX out from NEO-M9N
• RXI/SDI = RX into NEO-M9N

SPI

The NEO-M9N can also be configured for SPI communication. Connecting the DSEL pin to the SPI with the 2-pin jumper enables the SPI data bus thus disabling the UART functions on those lines. This also disables I²C interface.

Backup Battery

The small metal disk is a small lithium battery. This battery does not provide power to the IC like the 3.3V system does, but to relevant systems inside the IC that allow for a quick reconnection to satellites. The time to first fix will about ~29 seconds, but after it has a lock, that battery will allow for a two second time to first fix. This is known as a hot start and lasts for four hours after the board is powered down. The battery provides over a years worth of power to the backup system and charges slowly when the board is powered. To charge it to full, leave your module plugged in for 48 hours.

u.FL Connector

The MicroMod GNSS Function Board includes a u.FL connector for a secure connection with a patch antenna. Depending on the antenna, you may need a u.FL adapter to connect. The u.FL connector was added as a design choice for users that decide to place the MicroMod Main Board with the GNSS Function Board in an enclosure. With the u.FL adapter, the SMA connector can be mounted to the enclosure. For more information on working with u.FL connectors, we recommend checking out our tutorial about using u.FL connectors.

EEPROM

The board includes an I²C EEPROM. Unfortunately, this is not available for the user and was meant to hold board specific information.

LEDs

The board includes two status LEDs.

• 3V3: The 3V3 LED indicates when the board is powered. This LED is connected to the 3.3V line.
• PPS: The PPS LED is connected to the Pulse Per Second line. When connected to a satellite, this line generates a pulse that is synchronized with a GPS or UTC time grid. By default, you'll see one pulse a second.

Jumpers

The board includes a few jumpers to configure the NEO-M9N module. For more information, check out our tutorial on working with jumper pads and PCB traces.

• I²C Pull-up Resistors - This three way jumper labeled I2C connects two pull-up resistors to the I²C data lines. If you have many devices on your I²C data lines, then you may consider cutting these.
• WP - Adding solder to the jumper pad will disable write protect for the EEPROM.
• 3V3 - The jumper on the opposite side of the board with the label 3V3 is connected to the 3V3 LED. Cutting this jumper will disable the LED.
• PPS - The jumper on the opposite side of the board with the label PPS is connected to the PPS LED. Cutting this jumper will disable the LED.
• Bus Select
  • SPI - Connecting the DSEL pin to the SPI with the 2-pin jumper enables the SPI data bus thus disabling the UART functions on those lines. This also disables I²C interface.
  • DSEL - This pin is connected to the NEO-M9N's D_SEL pin to select the interface. Connecting this pin to either side will select the communication protocol.
  • Serial/I2C - Connecting the DSEL pin to the Serial/I2C with the 2-pin jumper disables the SPI data bus while keeping the UART and I²C interface available. The UART and I²C can also be enabled if the DSEL pin is open and not connected to either side. We recommend keeping the 2-pin jumper connected to avoid misplacing the component.
• SAFEBOOT - The PTH pads labeled as SAFEBOOT is used to start up the IC in safe boot mode, this could be useful if you somehow manage to corrupt the module's Flash memory. Breakaway a row of 2-pins from the header, solder the pins to the board, and connect a 2-pin jumper to enable the mode.

Jumpers (Top View)	Jumpers (Bottom View)

GPS Capabilities

The SparkFun GNSS Function Board NEO-M9N is able to connect to up to four different GNSS constellations at a time making it very accurate for its size. Below are the listed capabilities of the GPS unit when connecting to multiple GNSS constellations and when connecting to a single constellation.

When using a single GNSS constellation:

Hardware Pinout

Depending on your window size, you may need to use the horizontal scroll bar at the bottom of the table to view the additional pin functions. Note that the M.2 connector pins on opposing sides are offset from each other as indicated by the bottom pins where it says (Not Connected)*. There is no connection to pins that have a "-" under the primary function.

• MicroMod GNSS Function Board - NEO-M9N Pinout Table
• MicroMod General Pinout Table
• MicroMod General Pin Descriptions

Board Dimensions

The board uses the standard MicroMod Function Board size which measures about 1.50"x2.56".