SparkFun GPS-RTK Dead Reckoning ZED-F9R Hookup Guide

Contributors: bboyho, Elias The Sparkiest
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Hardware Overview (Breakout)

This hardware section will cover the breakout board for the GPS-RTK Dead Reckoning ZED-F9R. A majority of the images below will focus will on the u.FL version and will apply for the SMA version as well. While there are minor differences between the u.FL and SMA versions, the overall functionality of the boards is the same.

ZED-F9R u.FL V1.2 ZED-F9R SMA V1.1
ZED-F9R u.FL V1.2 ZED-F9R SMA V1.1

Some of the minor differences include differences in silkscreen. You will notice this with the acronyms for SPI (MOSI vs COPI, etc.). Of course, there is also a difference in the antenna connector: u.FL vs SMA connector.


Power for this board is 3.3V and we have provided multiple power options. This first and most obvious is the USB-C connector. Secondly, are the Qwiic Connectors on the left and right of the board. Thirdly, there is a 5V pin on the PTH header along the side of the board that is regulated down to 3.3V. Make sure that power you provide to this pin does not exceed 6 volts. Finally, both sides of the board includes a 3.3V pin (labeled as 3V3) that should only be provided with a clean 3.3V power signal. Of course, there is GND pins located through the board as well for reference ground.

Power and Ground Nets

Backup Battery

The small metal disk in the upper right corner next to the Qwiic connector 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 ~26 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.

Backup Battery for Hot Start


There are four LEDs on the bottom right of the board. Starting from the left:

  • PWR: The power LED labeled as PWR will illuminate when 3.3V is activated.
  • PPS: The pulse per second LED labelled as PPS will illuminate each second once a position lock has been achieved. This generates a pulse that is synchronized with a GPS or UTC time grid. By default, you'll see one pulse a second.
  • RTK: In u.FL v1.2 and SMA v1.2, the RTK LED is turned off by default. Once RTCM data has been successfully received it will begin to blink. This is a good way to see if the ZED-F9R is getting RTCM from various sources. Once an RTK fix is obtained, the LED will turn on. However, in u.FL v1.0, RTK LED is turned on by default. The LED will be illuminated constantly upon power up. Once RTCM data has been successfully received it will begin to blink. Once an RTK fix is obtained, the LED will turn off.
  • GEO: The GEO LED can be configured to turn on/off for geofencing applications.

Status LEDs


If you flip the board over, you will notice a few jumper pads. For more information on modifying the jumpers, check out our tutorial on working with jumper pads and PCB traces.

  • SHLD: This jumper connects the USB Type C connector's shield pin to GND. Cut this to isolate the USB Type C connector's shield pin. This was added in the u.FL breakout v1.2 and the SMA breakout v1.1.
  • I2C: 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.
  • SPI:The jumper labeled SPI which enables the SPI data bus thus disabling the UART functions on those lines. This also disables I2C interface.
  • PWR: Starting from the right side is a jumper labeled PWR. If you cut this trace, it will disconnect the Power LED.
  • PPS: On the left of the jumper is the PPS jumper that when cut disconnects the PPS LED.
  • GEO: Cutting the GEO jumper disconnect the LED used to indicate when we reach a certain condition for geofencing applications.
  • RTK: The RTK jumper disconnects the LED used for RTK applications.

Jumpers on the Back

U.FL vs SMA Connector

The ZED-F9R requires a good quality multi-band GNSS antenna. For those that using the u.FL version, you will need a u.FL to SMA cable to connect to a multi-band GNSS antenna. This is useful for those that are placing the board in an enclosure. We also have a SMA version for a sturdy connection.

ZED-F9R u.FL connector ZED-F9R SMA connector
ZED-F9R u.FL Connector ZED-F9R SMA Connector

Qwiic and I2C

There are two pins labeled SDA and SCL which indicates the I2C data lines. We also conveniently added a GND and 3.3V pin should you decide to daisy chain additional I2C devices. Similarly, you can use either of the Qwiic connectors to provide power and utilize I2C. The Qwiic ecosystem is made for fast prototyping by removing the need for soldering. All you need to do is plug a Qwiic cable into the Qwiic connector and voila!

I2C Pins and Qwiic connector


There are four pins on the right most header that are labeled with their corresponding SPI functionality. As mentioned in the jumpers section, you'll need to close the SPI jumper on the underside to enable SPI. Note that each version of the board uses different terminology for SPI. For more information, make sure to check out our SPI tutorial.

SPI Pins SPI Pins
SPI Pins on the u.FL and SMA Versions


There are two pins on the right most header currently labeled as MISO and MOSI. These are shared with the UART pins. By default, the UART interface is enabled. Be sure that the DSEL jumper on the back of the board is open.

  • TX/MISO/CIPO/POCI = TX out from ZED-F9R
UART Pins on u.FL Version UART Pins on SMA Version
UART Pins on the u.FL and SMA Versions


There is a second serial port available on the ZED-F9R. This is primarily used for RTCM3 correction data. By default, this port will automatically receive and parse incoming RTCM3 strings enabling RTK mode on the board like the other RTK breakout boards for the NEO-M8P-2 and ZED-F9P. The RTCM Correction port pins are arranged to match the industry standard serial connection (aka the 'FTDI' pinout). This pinout is compatible with our Bluetooth Mate and Serial Basic so you can send RTCM correction data from a cell phone or computer. Note that RTCM3 data can also be sent over I2C, UART1, SPI, or USB if desired.

UART2 RTCM Correction Source Port on u.FL Version UART2 RTCM Correction Source Port on SMA Version
UART2 Port on u.FL Version UART2 Port on SMA Version

Wheel Tick and Direction Pins

For advanced users that are interested in taking advantage of your vehicle's sensor readings, you can connect the following pins. Caution is advised however as this requires you to open up the hood of your car and hack into the its system.

  • D-: The reference GND pin (D-) when connecting the direction pin.
  • D+: The direction pin is labeled as (D+) tells the ZED-F9R what direction the vehicle is moving (forward/reverse).
  • W-: The reference GND pin (W-) when connecting the wheel tick pin.
  • W+: The wheel tick pin (W+) tells the ZED-F9R the distance a vehicle's wheel has traveled. Depending on the odometer type that you connect to, the ZED-F9R can also receive speed data from the vehicle.

Wheel Tick and Direction Pins

Broken Out Pins

There are five other pins broken out:

  • TXR: The transmit ready pin (TXR) enables a port to notify a device when bytes are ready to be transmitted.
  • RESET: The reset pin (RESET) resets the chip.
  • SFBT: The safeboot pin (SFBT) 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.
  • INT: The interrupt pin (INT) can be used to wake the chip from power save mode.
  • PPS: The pulse per second pin (PPS) outputs pulse trains synchronized with the GPS or UTC time grid. The signal defaults to once per second but is configurable over a wide range. Read the u-blox Receiver Protocol Specification in the Resources and Going Further tab for more information.

Other Micellaneous Pins Broken Out

3D IMU Orientation and Reference

For easy reference, we've documented the IMU's vectors with 3D Cartesian coordinate axes on the top and bottom side of the board. Make sure to orient and mount the board correctly so that the ZED-F9R can accurately calculate navigation information. Remember, it's all relative.

9DoF Reference (Top View) 9DoF Reference (Bottom View)
9DoF Reference (Top View) 9DoF Reference (Bottom View)

GPS Capabilities

The ZED-F9R is able to connect to up to four different GNSS constellations simultaneously with the 3D gyro and 3D accelerometer making it very accurate for its size. Below are the listed capabilities of the GPS unit.

Parameter Specification
Max navigation update rate (RTK) Priority navigation mode 30 Hz
Non-Priority navigation mode 2 Hz
Velocity Accuracy 0.05m/s
Dynamic Attitude Accuracy Heading 0.2 degrees
Pitch 0.3 degrees
Roll 0.5 degrees
Navigation Latency Priority Navigation Mode 15ms
Max Sensor Output Rate 100Hz
Time-To-First-Fix Cold Start 26s 25s 30s 25s 28s
Hot Start 2s 2s 2s 2s 2s
Aided Start 3s 3s 3s 3s 3s
Re-convergence time RTK ≤ 10s ≤ 10s ≤ 10s ≤ 10s ≤ 30s
SensitivityTracking and Navigation -160dBm -160dBm -160dBm -160dBm -160dBm
Reacquisition -157dBm -157dBm -157dBm -157dBm -157dBm
Cold Start -147dBm -147dBm -147dBm -147dBm -145dBm
Hot Start -158dBm -158dBm -158dBm -158dBm -158dBm

Performance in Different GNSS Modes from the ZED-F9R Datasheet

Horizontal Position Accuracy PVT1.5m CEP1.5m CEP1.5m CEP1.5m CEP1.5m CEP
SBAS1.0m CEP1.0m CEP1.0m CEP1.0m CEP1.0m CEP
+ 1ppm CEP
+ 1ppm CEP
+ 1ppm CEP
+ 1ppm CEP
+ 1ppm CEP
Vertical Position AccuracyRTK0.01m
+1ppm R50
+1ppm R50
+1ppm R50
+1ppm R50
+1ppm R50

Position accuracy in Different GNSS Modes from the ZED-F9R Datasheet

Board Dimensions

Overall, both versions of the breakout board is 2.00"x1.70". There are 4x mounting holes by each corner of the board. Note that the SMA connector increases the length of the board slightly and you will need to attach a GNSS antenna to that connector as well.

Board Dimensions for u.FL version Board Dimensions for SMA version
Board Dimensions for u.FL version Board Dimensions for SMA version