Hardware Overview

Introduction

SparkFun GNSS Flex Breakout
SKU: GPS-28137

Purchase from SparkFun
The SparkFun GNSS Flex Breakout board is a carrier board for our SparkPNT GNSS Flex modules. With pre-soldered headers, the GNSS Flex Breakout board provides access to all of the interfaces from a GNSS Flex module. We have also included two 6-pin JST connectors, same as the ones used on Pixhawk flight controllers. The JST connectors allow you to: connect the GNSS to a Pixhawk; or connect a radio to transfer RTCM correction data. Power can be provided by any or all of: the USB connectors or the VIN breakout pin.

The GNSS Flex Breakout comes populated with two sets of 2x10 pin, 2mm pitch male headers for attaching a GNSS Flex module. With these headers, the GNSS Flex system is designed to be modular so that boards are pin-compatible for upgrades and can be easily swapped for repairs. Depending on the capabilities of the GNSS Flex module that is connected, these pins will breakout the USB, UART (x4), I²C, and SD card interfaces for the GNSS receiver along with any PPS (x2) or event (x2) signals, using a standardized pin out. There board also has four LEDs indicators for power and the PPS1, PVT, and RTK signals from the GNSS Flex module.

Note

By default, the CH342 USB-to-Serial converter chip is connected to both the GNSS UART1 and UART2 interfaces. When you connect the UART USB port to your computer and install the driver, those two UART interfaces will appear as COM ports. If you need dedicated access to the UART1 or UART2 breakout pins, or want to use either of the JST connectors, you will need to disable the CH342. On this board, we have made this simple; just pull the CH342 EN breakout pin LOW or connect it to GND. Otherwise, there is also a CH342 EN jumper you can solder instead.

By default, Pin 1 of the JST connectors provides 5V output. But jumpers on the board allow the voltage to be changed to 3.3V. Or you can isolate the other power sources and connect an external 5V power input on Pin 1 instead. It is up to you.

Design Files

Design Files
3D ModelDimensions

Manipulate 3D Model

Controls Mouse Touchscreen

Zoom Scroll Wheel 2-Finger Pinch

Rotate Left-Click & Drag 1-Finger Drag

Move/Translate Right-Click & Drag 2-Finger Drag

Dimensions of the GNSS Flex Breakout board.

Need more measurements?

For more information about the board's dimensions, users can download the KiCad files for this board. These files can be opened in KiCad and additional measurements can be made with the measuring tool.

KiCad - Free Download!

KiCad is free, open-source CAD program for electronics. Click on the button below to download their software. (*Users can find out more information about KiCad from their website.)

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Measuring Tool

This video demonstrates how to utilize the dimensions tool in KiCad, to include additional measurements:

Board Layout

The GNSS Flex system is designed around two 2x10-pin, 2mm pitch headers used mate the two types of boards. A standardized pin layout, keeps the ecosystem pin-compatible for upgrades and allows board to be easily swapped for repairs. Depending on the capabilities of the GNSS receiver, these pins will breakout the USB, UART (x4), I²C, and SD card interfaces along with any PPS or event signals of the GNSS receiver.

The GNSS Flex Breakout has the following features:

GNSS Flex Headers

Two sets of 2x10 pin, 2mm pitch female headers for connecting a GNSS Flex module.
Alignment Indicator

Used to indicate the board alignment of a GNSS Flex module.
Signal Bridges

Two U.FL-to-SMA signal bridges, provide on-board adapters for connecting an external GNSS antenna(s) or another input/output signal(s).
Status LEDs

Four status indication LEDs for the attached GNSS Flex module.
USB-C Connectors

Used to access the USB and UART1/UART2 interfaces of a GNSS Flex Module.
JST Connectors

Breaks out the UART1, UART2, and I²C, and interfaces of a GNSS Flex Module to connect a PixHawk controller or telemetry radio.
SD Card Slot

Depending on the capabilities of the GNSS Flex module, a µSD card slot is available for data logging.
Qwiic Connector

Depending on the capabilities of the GNSS Flex module, a Qwiic connector is available for connecting to a controller.

USB Connectors

Depending on the capabilities of the GNSS receiver, the USB connectors will break out the USB interface and/or UART interfaces from the GNSS Flex module.

USB USB-C connector
- If available, connects directly w/ GNSS Flex Module's USB interface
- 5V power input
UART USB-C connector
- Interfaces to UART1 and UART2 on the GNSS Flex Module via a CH342 USB-to-Serial converter
- 5V power input
Info

To utilize the PTH pins or JST connections of the UART1 and UART2 interfaces, the CH342 USB-to-Serial converter must be disabled with either the CH342 EN jumper or the CH342 EN PTH pin.

SMA Connectors

The SMA connectors, provide users with a more robust connection for interfacing with signals to/from the GNSS Flex module. Each pair of U.FL and SMA connectors are bridged together and their ground plane isolated from the rest of the board, this allows users to pass signals between the GNSS Flex module and the GNSS Flex Breakout board. On the GNSS Flex Breakout board, we provide two sets of signal bridges. These signal bridges will primarily be used to attach an external GNSS antenna for their GNSS Flex module.

Signal bridges — The RF signal bridges on the GNSS Flex Breakout, which provides a more robust SMA connection.

Breakout Pins

The primary function of the SparkFun GNSS Flex Breakout board is to expose the interfaces of the GNSS Flex modules. Most of which, are provided through the PTH pins.

Breakout Pins and Exposed Interfaces:

Power Pins
- VIN
- 5V
- 3.3V
- 3.3V Enable
- Backup power
- Reset
USB data
UART (x4)
SD card (see SD Card Slot)
I²C bus
PPS signals (x2)
Status indicators (x2)
Event triggers (x2)
ID pin

Power

The simplest method to power the GNSS Flex breakout board is through the USB-C connectors. However, only 3.3V is required to power an attached GNSS Flex module; the 5V is only utilized for the USB interface and to power the JST connectors.

Below, is a general summary of the power circuitry on the board; most are broken out as PTH pins:

Power Supplies - Power sources for the entire board
- VIN - The general input voltage
- 5V - The voltage from the USB-C connector, usually 5V.
  - Input Voltage Range: 2.2 - 5.5V (1)
  - Powers the 3.3V voltage regulators
    - AP7361C, which can source up to 1.5A
    - RT9080, which can source up to 600mA
  - They also power the JST connectors
3V3 - Provides a regulated 3.3V from the AP7361C, using the power supplied from the VIN, 5V, and/or USB-C connectors
- Used to power the GNSSS Flex module, LEDs, and Qwiic connectors
- Controlled by the 3V3 EN pin, which is enabled by default
3V3 EN - Enables the voltage output from the AP7361C, 3.3V voltage regulator
- Enabled by default (active HIGH)
VBACKUP - Provides a regulated 3.3V from the RT9080, using the power supplied from the VIN, 5V, and/or USB-C connectors
- Provides backup power to the GNSS Flex module to maintain ephemeris data for warm starts
RESET - Used to reset the GNSS Flex module
GND - The common ground or the 0V reference for the voltage supplies.

The RT9080 LDO regulator has an input voltage range of 1.2 - 5.5V and the AP7361C LDO regulator has an input voltage range of 2.2 - 6.0V. A minimum supply voltage of 3.5V is recommended for a 3.3V output.

Backup Battery

When connecting an external battery or power source to the VBACKUP pin, users should disconnect the VBACKUP jumper.

JST Connector

The VOUT pins for the JST connectors are designed to operate as a voltage output. However, an input voltage can be supplied through the pin, but users should be mindful of any voltage contention issues.

Additionally, the jumper for the VOUT pin can be modified to change to output voltage level.

Info

For more details, users can reference the schematic and the datasheets of the individual components on the board.

Interfaces

The following interfaces and signals of the GNSS Flex system are connected to the 40-pin female GPIO header of the GNSS Flex Breakout board. Below, are tables detailing the pin connections for each interface.

USBUARTI²CPPS SignalsEvent TriggersStatus IndicatorsID Pin

If available, the USB interface of the GNSS Flex module can be accessed through the USB USB-C connector.

UART Numbering

Please note that the UART numbers (UART1 - UART4) listed below follows the GNSS Flex Module UART numbering scheme.

The pin connections of the UART interfaces, from the GNSS Flex system on the GNSS Flex breakout board.

UART1: The UART1 interface can be accessed through either the UART USB-C connector, COM1 + I²C JST connector, or RX1/TX1/CTS1/RTS1 set of PTH pins. However, in order to utilize the COM1 + I²C JST connector or RX1/TX1/CTS1/RTS1 PTH pins, the CH342 must be disabled using either the CH342 EN jumper or the CH342 EN PTH pin.
UART2: The UART2 interface can be accessed through either the UART USB-C connector, COM2 JST connector, or RX2/TX2/CTS2/RTS2 set of PTH pins. However, in order to utilize the COM2 JST connector or RX2/TX2/CTS2/RTS2 PTH pins, the CH342 must be disabled using either the CH342 EN jumper or the CH342 EN PTH pin.
UART3: The UART3 interface can be accessed through the RX3/TX3/CTS3/RTS3 set of PTH pins.
UART4: The UART4 interface can be accessed through the RX4/TX4 PTH pins.

The I²C interface can be accessed through either the Qwiic connector, COM1 + I²C JST connector, or SCL/SDA PTH pins. Depending on how the I²C bus is configured, users may need to use pull-up resistors, which can be enabled with the I^2^C jumper.

I2C interface — The pin connections of the I²C interface, from the GNSS Flex system on the GNSS Flex breakout board.

The two PPS signals can be accessed through the PPS1 and PPS2 PTH pins. The PPS1 pin is also connected to the PPS LED, which can be disabled with a jumper for low power applications.

The two event triggers can be accessed through the EVENTA and EVENTB PTH pins.

There are two status indicators, which can be accessed through the PVT and RTK PTH pins. These pins are also connected to the PVT and RTK LEDs, which can be disabled with their respective jumpers for low power applications.

The ID pin can be utilized to identify the GNSS receiver of a connected GNSS Flex module.

GNSS Flex Module	ID Resistors	ID Value
mosaic-X5	1.0kΩ + 47.0kΩ	0.06875V
LG290P	3.3kΩ + 10.0kΩ	0.81880V
DAN-F10	5.62kΩ + 6.8kΩ	1.49324V
ZED-X20P	15.0kΩ + 12.1kΩ	1.82657V

LEDs

There are four status LEDs on the GNSS Flex Breakout:

PWR - Power (Red)
- Turns on once power is supplied to the board
PPS - Pulse-Per-Second (Yellow)
- Indicates when there is a pulse-per-second signal from the GNSS Flex module
RTK - RTK (White)
- Usually indicates when an RTK fix has been established or when the correct RTCM data is being received by the GNSS Flex module
PVT - PVT (Blue)
- Usually indicates when an GNSS lock or a position fix has been established by the GNSS Flex module

Info

For low power applications, the LEDs can be disabled to conserve energy. See the Jumpers section.

JST Connectors

There are two locking JST-GH connectors to easily access the UART and I²C interfaces of the GNSS Flex headers. Depending on the capabilities of the GNSS Flex module, the UART and I²C interfaces could be used to configure and communicate with the GNSS receiver.

COM1 + I²C
- Breaks out the UART1 and I²C interfaces for a connection to a Pixhawk flight controller
- 5V power output
COM2
- Breaks out the UART2 interface (w/ flow control) for connection to a telemetry radio
- 5V power output

Power Options

By default, the locking JST connectors provide a 5V power output. However, an optional 3.3V power output can be configured by modifying the jumpers underneath the connectors, on the opposite side of the board.

These connector can also function as an optional 5V power input, when all other power sources have been disconnected from the GNSS Flex Breakout board.

Pin Connections

Below, are tables of the pin connections of each JST connector:

`COM1 + I²C`
Pin Number	1 (Left Side)	2	3	4	5	6 (Right)
Label	`5V`	`TXD1`	`RXD1`	`SCL`	`SDA`	`GND`
Function	Power: 5V	UART - Transmit	UART - Receive	I²C - Clock	I²C - Data	Ground

`COM2`
Pin Number	1 (Left Side)	2	3	4	5	6 (Right)
Label	`5V`	`TXD2`	`RXD2`	`CTS2`	`RTS2`	`GND`
Function	Power: 5V	Transmit	Receive	Clear-to-Send	Ready-to-Send	Ground

SD Card Slot

Depending on the capabilities of the GNSS receiver, the µSD card slot can be used for data logging.

Qwiic Connector

The Qwiic connector is attached to the I²C interface of the GNSS Flex headers. Depending on the capabilities of the GNSS Flex module, the I²C interface could be used to configure and communicate with the GNSS receiver.

What is Qwiic?

The Qwiic connect system is a solderless, polarized connection system that allows users to seamlessly daisy chain I²C boards together. Play the video, to learn more about the Qwiic connect system or click on the banner above to learn more about Qwiic products.

Features of the Qwiic System

No SolderingPolarized ConnectorDaisy Chain-able

no soldering - light theme no soldering - dark theme

Qwiic cables (4-pin JST) plug easily from development boards to sensors, shields, accessory boards and more, making easy work of setting up a new prototype.

polarized connector - light theme polarized connector - dark theme

There's no need to worry about accidentally swapping the SDA and SCL wires on your breadboard. The Qwiic connector is polarized so you know you’ll have it wired correctly every time.

The part numbers for the PCB connector is SM04B-SRSS (Datasheet) and the mating connector on the cables is SHR04V-S-B; or an equivalent 1mm pitch, 4-pin JST connection.

daisy chainable - light theme daisy chainable - dark theme

It’s time to leverage the power of the I²C bus! Most Qwiic boards will have two or more connectors on them, allowing multiple devices to be connected.

Jumpers

There are twelve jumpers on the GNSS Flex Breakout:

Never modified a jumper before?

Check out our Jumper Pads and PCB Traces tutorial for a quick introduction!

How to Work with Jumper Pads and PCB Traces

Jumpers on the bottoms of the breakout board — Jumpers on the bottom of the GNSS Flex Breakout board.

The jumpers for the status LEDs, can be cut to disable the associated LED.

PWR - Power (Red)
PPS - Pulse-Per-Second (Yellow)
RTK - RTK (White)
PVT - PVT (Blue)

SHLD: These jumpers can be cut to isolate the shielding of the associated USB-C connector from the ground plane of the board.
VOUT: These jumpers can be modified to configure the I/O voltage of the JST connectors between 3.3V or 5V.
I2C: This jumper, next to the Qwiic connector, can be bridged to attach 2.2kΩ pull-up resistors to the I²C bus.
VBACKUP: This jumper can be disconnected to allow for an external battery to be connected VBACKUP PTH pin.
CH342 EN: This jumper can be shorted, to disable the CH342 USB-to serial converter. This allows the UART interfaces to be accessed from the PTH or JST connections, instead of their USB connection.
MEAS: This jumper can be utilized to measure the current coming into the 5V power rail from either of the USB and/or VIN power sources.

Controls	Mouse	Touchscreen
Zoom	Scroll Wheel	2-Finger Pinch
Rotate	`Left-Click` & Drag	1-Finger Drag
Move/Translate	`Right-Click` & Drag	2-Finger Drag