SparkFun GPS-RTK Dead Reckoning ZED-F9K Hookup Guide

2022-05-17 | By SparkFun Electronics

License: See Original Project

Courtesy of SparkFun

Guide by BBOYHO, ELIAS THE SPARKIEST

Introduction

The SparkFun GPS ZED-F9K takes advantage of dead reckoning for navigation. The u-blox ZED-‎F9K is a powerful GPS-RTK unit that uses a fusion of IMU, wheel ticks, a vehicle dynamics model, ‎correction data, and GNSS measurements to provide highly accurate and continuous position for ‎navigation in the difficult conditions. We will quickly get you set up using the Qwiic ecosystem ‎through Arduino so that you can start reading the output!‎

SparkFun GNSS-RTK Dead Reckoning Breakout - ZED-F9K (Qwiic)‎

Required Materials

To follow along with this tutorial, you will need the following materials at a minimum. You may not ‎need everything though depending on what you have. Depending on your application, you may ‎need additional parts for a correction source or connecting to you a vehicle to obtain wheel ‎tick/direction information. Add it to your cart, read through the guide, and adjust the cart, as ‎necessary.‎

ZED-F9K Wishlist SparkFun Wish List

Microcontroller

If you are using the breakout board and programming in Arduino, we recommend the SparkFun ‎Thing Plus - ESP32 WROOM with the associated USB cable to start.‎

Antenna

We recommend using the magnetic mount antenna for the full RF reception and mounting it on top ‎of a vehicle. The antenna uses an SMA connector so you can directly connect it to the breakout ‎board. Link for that is below in the antenna accessories. The length of the antenna cable was also ‎useful in mounting it.‎

GNSS Multi-Band Magnetic Mount Antenna - 5m (SMA)‎
GNSS Multi-Band L1/L2 Surveying Antenna (TNC) - TOP106‎
GNSS Multi-Band L1/L2 Helical Antenna (SMA) BT-560‎
MagmaX2 Active Multiband GNSS Magnetic Mount Antenna - AA.200‎

Note: If you want to try different chip antennas, you can try the following antennas. However, these ‎antennas will not provide the full RF reception for the ZED-F9K.

GPS Antenna Accessories

Depending on your antenna, you will need an adapter to connect to the GPS-RTK's u.FL connector. ‎If you need more than the metal from the top of a vehicle or are mounting it on a robot that does ‎not have the necessary ground plane, you can use the GPS antenna ground plate to improve your ‎GPS antenna's performance. If you are using the GNSS Multi-Band L1/L2 Surveying Antenna (TNC) ‎‎- TOP106, you'll need to grab the interface cable.‎

Interface Cable - SMA Male to TNC Male (300mm)‎
GPS Antenna Ground Plate

Other Qwiic Cable Accessories

There are different Qwiic cable lengths available. Depending on your application, you can adjust it ‎to your project's specifications.‎

Heads up! If you are using the RedBoard without a Qwiic connector, we recommend getting the ‎Qwiic Shield for Arduino.

SparkFun Qwiic Shield for Arduino

Suggested Reading

If you aren't familiar with the Qwiic system, we recommend reading here for an overview.‎

qwiic_1

Qwiic Connect System

We would also recommend taking a look at the following tutorials if you aren't familiar with them.‎

GPS Basics: The Global Positioning System (GPS) is an engineering marvel that we all have ‎access to for a relatively low cost and no subscription fee. With the correct hardware and minimal ‎effort, you can determine your position and time almost anywhere on the globe.‎
Serial Peripheral Interface (SPI): SPI is commonly used to connect microcontrollers to ‎peripherals such as sensors, shift registers, and SD cards.‎
I2C: An introduction to I2C, one of the main embedded communications protocols in use today.‎
How to Work with Jumper Pads and PCB Traces: Handling PCB jumper pads and traces is an ‎essential skill. Learn how to cut a PCB trace, add a solder jumper between pads to reroute ‎connections, and repair a trace with the green wire method if a trace is damaged.‎
Getting Started with U-Center for u-blox: Learn the tips and tricks to use the u-blox software ‎tool to configure your GPS receiver.‎
ESP32 Thing Plus Hookup Guide: Hookup guide for the ESP32 Thing Plus using the ESP32 ‎WROOM's Wi-Fi/Bluetooth system-on-chip in Arduino.‎

What is Dead Reckoning?‎

Dead Reckoning is the process of determining current position by combining previously determined ‎positional data with speed and heading. This process can also be applied to ‎determine future positions as well! The ZED-F9K uses Dead Reckoning which calculates speed and ‎heading (amongst many other points of data) through the use of an internal inertial measurement ‎unit (IMU). The addition of a wheel ticks, RTCM-formatted corrections, and IMU allows the ZED-‎F9K to produce high precision and more accurate readings in between GNSS data refreshes!‎

In addition, the module can also give accurate and useful GNSS data in areas where satellite ‎connections are difficult to maintain areas like the dense urban environments of major cities, long ‎tunnels, parking garages, any large UFO's that may descend from the sky, etc.‎

Dead Reckoning Overview

As mentioned in the "What is Dead Reckoning?" section, the u-blox F9K module has an internal ‎inertial measurement unit or IMU for short. The IMU calculates position based on the last GNSS ‎refresh and its own movement data points. To use the SparkFun GPS-RTK Dead Reckoning Board, ‎there are a few guidelines to orienting and mounting the module to a vehicle that are outlined from ‎u-blox. For more detailed information, check out the integration manual for mounting.‎

ZED-F9K INTEGRATION MANUAL (PDF)‎

Orientation for the SparkFun Dead Reckoning

The SparkFun Dead Reckoning adheres to two particular frames of reference: one frame of ‎reference for the car and the second a geodetic frame of reference anchoring it to the globe. The ‎latter, known as the local level frame, uses the following as its' axes:‎

X-axis points to the North
Y-axis points to the East
Z-axis uses the right-hand system by pointing down.‎

This frame will be referred to by its acronym NED (North-East-Down) in the image below.‎

The second frame of references is the Body-Frame reference and uses the following as its' axes.‎

X-axis points to the front of the vehicle
Y-axis points to the right of the vehicle
Z-axis uses the right-hand system by pointing down.‎

You can reference the Body-Frame axes directly on the SparkFun Dead Reckoning ZED-F9K ‎breakout board by looking for the silkscreen with the xyz axis.‎

top_2

Top View with the Axis for Reference

bottom_3

Bottom View with the Axis for Reference

Vehicle Attitude

The transformation of the vehicle within these two frames are given as heading, pitch, and roll. In ‎the datasheet these three angles are called the vehicle's attitude. Below is an image that ‎illustrates how all of these elements fit together.‎

output_4

Vehicle attitude output as shown on page 30 of the Integration Manual (UBX-20046189-R02)‎

Mounting the SparkFun Dead Reckoning ZED-F9K

The only guideline here is that the SparkFun Dead Reckoning is stable within 5 degrees, and of ‎course that the X-axis points towards the front of the car as mentioned above. Below is an image ‎that illustrates the ZED-F9K with the installation frame as opposed to the vehicle frame.‎

frame_5

Installation frame as shown on page 19 of the Integration Manual (UBX-20046189-R02)‎

With the physical board mounted, it will look similar to the following image.‎

board_6

In the images above, the SparkFun Dead reckoning is seen in the front, driver's side of the car and ‎it may be tempting to think that this is also a necessary requirement. However, it can be mounted ‎anywhere within the vehicle (or RC-car, or boat). Keep in mind that the pitch and roll is relative to ‎the SparkFun Dead Reckoning's position.‎

Calibration

After you've mounted the SparkFun Dead Reckoning ZED-F9K, there is still a calibration phase to ‎complete that must satisfy the following movements:‎

First, the car needs to be stopped with the engine turned on.
Secondly, the car must do left and right-hand turns.
Lastly, the car must reach a speed over 30 km/h‎.

In SparkFun's u-blox Arduino library, SparkFun has included the calibration example, which prints ‎out the module's calibration status.‎

Hardware Overview

Note: Overall, the ZED-F9K module's specifications are similar to the ZED-F9R module. The ‎difference is that the ZED-F9K is rated as automotive grade while the ZED-F9R is professional ‎grade. For more information about the different product grades, check out the page on u-blox ‎Product Grades. ‎

Comparing the breakout boards, the ZED-F9K breakout board includes an SMA connector instead ‎of the u.FL connector.‎

Power

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, just ‎below the 5V pin is a 3.3V pin that should only be provided a clean 3.3V power signal.‎

power_7

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.‎

battery_8

LEDs

There are four LEDs on the bottom left 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: The RTK LED will be illuminated constantly upon power up. Once RTCM data has been ‎successfully received it will begin to blink. This is a good way to see if the ZED-F9K is getting ‎RTCM from various sources. 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.‎

led_9

Jumpers

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.‎

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_10

SMA Connector

The ZED-F9K requires a good quality GPS or GNSS (preferred) antenna. A SMA connector is ‎provided for a secure connection. To get the best out of your ZED-F9K, make sure to get a GNSS ‎multi-band antenna.‎

connector_11

Qwiic and I²C

There are two pins labeled SDA and SCL which indicates the I²C data lines. 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!‎

qwiic_12

The only I²C address for this and all u-Blox GPS products is 0x42, though each can have their ‎address changed through software.‎

SPI

There are four pins on the right most header that are labeled with their corresponding SPI ‎functionality. As mentioned in the jumper’s section, you'll need to close the SPI jumper on the ‎underside to enable SPI.‎

spi_13

UART

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 = TX out from ZED-F9K
RX/MOSI = RX into ZED-F9K

utop_14

Top View

bbottom_15

Bottom View

There is a second serial port available on the ZED-F9K. 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 Serial Basic so you can send RTCM ‎correction data from a computer. Note that RTCM3 data can also be sent over I2C, UART1, SPI, or ‎USB if desired.‎

second_16

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 its system.‎

D-: The reference GND pin (D-) when connecting the direction pin.
D+: The direction pin is labeled as (D+) tells the ZED-F9K 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-F9K the distance a vehicle's wheel has traveled. ‎Depending on the odometer type that you connect to, the ZED-F9K can also receive speed ‎data from the vehicle.‎

wheel_17

Broken Out Pins

There are four other pins broken out:‎

pins_18

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.‎

broken_19

‎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-F9K can accurately calculate navigation information. Remember, it's all relative.‎

9top_20

‎9DoF Reference (Top View)‎

9bottom_21

9DoF Reference (Bottom View)‎

GPS Capabilities

The ZED-F9K 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.‎

gps_23

Performance in Different GNSS Modes from the ZED-F9K Datasheet

gps_24

Performance in Single-GNSS Modes from the ZED-F9K Datasheet

Board Dimensions

Overall, the board is about 2.00" x 1.70" (50.8mm x 43.2mm). With the USB and SMA connector, it's ‎about 2.40" 1.70" (61.0mm x 43.2mm). There are 4x mounting holes by each corner of the board.‎

dim_25

Hardware Assembly

For this example, I used a SparkFun Thing Plus - ESP32 WROOM and associated USB cable. ‎Connecting the boards with Qwiic cable, the assembly is very simple. Plug a Qwiic cable between ‎the Thing Plus - ESP32 WROOM and SparkFun GPS RTK Dead Reckoning ZED-F9K. Then plug in ‎one of our patch antennas to the SMA connector If you're going to be soldering to the through hole ‎pins for I²C functionality, then just attach lines to power, ground, and the I²C data lines to a ‎microcontroller of your choice.‎

When using the ZED-F9K, you will want to orient the board according to the guidelines explained ‎earlier. Below is a top-down view with the board pointing up. Your setup should look similar to the ‎image below.‎

assembly_26

Make sure to secure the board above a vehicle's dashboard using some tape or sticky tack when ‎prototyping and testing. For best signal reception, it is suggested to guide the antenna from the ‎inside of the car and through a window before attaching the GPS on top of a car. We recommend ‎the magnetic mount GPS/GNSS antenna to easily mount.‎

mount_27

Adding a RTCM Correction Source

To get the most out of the ZED-F9K you will need an RTCM correction source. There are a few ‎methods of adding a RTCM correction source. If you have been following along with our GPS-RTK ‎and GPS-RTK2, you can pipe correction data from a wireless network, LoRa, or cellular network. ‎Depending on your setup, you will probably need a ZED-F9P for a correction source. For more ‎information, check out these tutorials.‎

rtk_29

What is GPS RTK?

‎Learn about the latest generation of GPS and GNSS receivers to get 14mm positional accuracy!‎

diy_30

How to Build a DIY GNSS Reference Station

Learn how to affix a GNSS antenna, use PPP to get its ECEF coordinates and then broadcast your ‎own

RTCM data over the internet and cellular using NTRIP to increase rover reception to 10km!‎

rover_31

Setting up a Rover Base RTK System

Getting GNSS RTCM correction data from a base to a rover is easy with a serial telemetry radio! ‎

We'll show you how to get your high precision RTK GNSS system setup and running.‎

Software Installation

Note: This example assumes you are using the latest version of the Arduino IDE on your desktop. ‎If this is your first time using Arduino, please review our tutorial on installing the Arduino IDE. If you ‎have not previously installed an Arduino library, please check out our installation guide.‎

All of our u-blox based GPS boards share the same library: the breakout board, ‎their predeccesors and the higher precision u-blox cousins. The SparkFun u-blox Arduino library ‎can be downloaded with the Arduino library manager by searching 'SparkFun u-blox GNSS' or you ‎can grab the zip here from the GitHub repository to manually install. Once calibrated, you can take ‎advantage of the examples for the ZED-F9K.‎

SPARKFUN U-BLOX ARDUINO LIBRARY (ZIP)‎

There are 13 example sketches provided to get you up and receiving messages from space. The ‎examples listed below highlight the additional capabilities of the SparkFun Dead Reckoning ZED-‎F9K. For the scope of this tutorial, we will not focus on the basic GPS polling sketches as shown in ‎the other u-blox hookup guides.‎

Note: Example 2 uses the 'MicroNMEA' library by Steve Marple. Make sure to install the library as ‎well by searching for it in the Arduino library manager. You could also grab the zip here from ‎the GitHub repository to manually install.

MICRONMEA ARDUINO LIBRARY (ZIP)‎

Arduino Examples

Heads up! Make sure stay focused when driving and obey all traffic laws when driving. Ensure that ‎you are not distracted while operating a vehicle and are aware of your surroundings. For each ‎example, make sure to plan your route accordingly to achieve the maneuvers. If you need, grab a ‎friend and adult as you ride in the passenger seat. After you attempt these movements, park your ‎car in a safe location and turn your engine off before checking the status or monitoring the ‎readings!‎

Example 1 - Calibrate Sensor

Now that the GPS-RTK SparkFun Dead Reckoning is mounted and oriented correctly with regards ‎to the vehicle, it's time to calibrate the sensor. To do this, a few movements with the vehicle must ‎be done all while maintaining good GNSS reception.‎

First, the car needs to be stopped with the engine turned on.‎
Secondly, the car must do left and right-hand turns.‎
Lastly, the car must reach a speed over 30 km/h.‎

For the first example (located in File Examples > SparkFun u-blox GNSS Arduino ‎Library > Dead Reckoning > Example1_calibrateSensor), the calibration status will be printed ‎to the Arduino's serial monitor to indicate when calibration is ongoing and when it has completed.

‎If you have not already, select your Board (in this case the SparkFun ESP32 Thing Plus), and ‎associated COM port. Upload the code to the board and set the serial monitor to 115200 ‎baud. Perform those fancy maneuvers (while obeying the traffic laws) before parking your car in a ‎safe location. Then turn your engine off before checking the status! You should see a message ‎indicating that the ZED-F9P is calibrated. If you do not, try driving around with the board once again!‎

Example 2 - IMU Data

After you have your sensor calibrated (see example1), you can now poll the internal IMU to see ‎what data is being fed to the GNSS calculations. Open the second example (located in File ‎Examples > SparkFun u-blox GNSS Arduino Library > Dead ‎Reckoning > Example2_getIMUData) to follow along! First, the sketch checks to see that the ‎board is calibrated before it attempts to read IMU data.‎

If you have not already, select your Board (in this case the SparkFun ESP32 Thing Plus), and ‎associated COM port. Upload the code to the board and set the serial monitor to 115200 baud. ‎This may be a good time to bring a friend along to drive if you decide to actively monitor the output. ‎Otherwise, check out the data after taking the board for a stroll. Try driving around as the board ‎senses the car's movement. Then park in a safe location with the engine turned off before ‎inspecting the data.‎

Example 4 - Vehicle Dynamics

What happened to Example 3? It's been skipped over because it’s used primarily as a diagnostic ‎sketch. What sensors are currently being used, are they functioning correctly, are the ‎measurements being listed as bad or non-existent? Example 3 helps diagnose these various issues. ‎Let’s move ahead to the fourth example in the library (located in File Examples > SparkFun u-‎blox GNSS Arduino Library > Dead Reckoning > Example4_vehicleDynamics)

‎The vehicle attitude is a termed coined by u-blox that encompasses three measurements: vehicle ‎pitch, vehicle roll, and vehicle heading. Much like the other example sketches, this one checks ‎to make sure that the SparkFun Dead Reckoning ZED-F9K has been calibrated before pulling data. ‎If the SparkFun Dead Reckoning ZED-F9K has indeed been calibrated, then it gets the relevant ‎information by calling myGNSS.getVehAtt(). As in Example 2, the data is stored within ‎a struct called vehAtt.‎

Connecting the GPS-RTK to a Correction Source

rtk_29

What is GPS RTK?‎

Learn about the latest generation of GPS and GNSS receivers to get 14mm positional accuracy!‎

diy_30

How to Build a DIY GNSS Reference Station

Learn how to affix a GNSS antenna, use PPP to get its ECEF coordinates and then broadcast your ‎own

RTCM data over the internet and cellular using NTRIP to increase rover reception to 10km!‎

rover_31

Setting up a Rover Base RTK System

‎Getting GNSS RTCM correction data from a base to a rover is easy with a serial telemetry radio! ‎

We'll show you how to get your high precision RTK GNSS system setup and running.‎

Resources and Going Further

Ready to get hands-on with GPS?‎

ready_28

We've got a page just for you! We'll walk you through the basics of how GPS ‎works, the hardware needed, and project tutorials to get you started.‎

TAKE ME THERE!‎

Now that you've successfully got your GPS receiver up and running, it's time to incorporate it into ‎your own project! For more information, check out the resources below:‎