SparkFun GPS-RTK Dead Reckoning ZED-F9R Hookup Guide

2022-01-11 | By SparkFun Electronics

License: See Original Project Single Board Computers

Courtesy of SparkFun

GUIDE BY BBOYHO, ELIAS THE SPARKIEST

Introduction

The SparkFun GPS ZED-F9R is the next iteration of u-blox's GPS offerings! This version takes advantage of dead reckoning for navigation. The u-blox ZED-F9R 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 and Python so that you can start reading the output!

Required Materials

To follow along with this tutorial, you will need the following materials. You may not need everything though depending on what you have. The Wishlist on the left is for the ZED-F9R breakout board. The Wishlist on the right includes parts for the ZED-F9R pHAT. Both include parts at a minimum to get the ZED-F9R up and running. Depending on your application, you may need additional parts for a correction source or connecting to you a vehicle to obtain heel tick/direction information. Add it to your cart, read through the guide, and adjust the cart as necessary.

ZED-F9R Breakout Parts SparkFun Wish List

GNSS Multi-Band Magnetic Mount Antenna - 5m (SMA)
SparkFun GPS-RTK Dead Reckoning Breakout - ZED-F9R (Qwiic)
Interface Cable SMA to U.FL
Qwiic Cable - 100mm
USB micro-B Cable - 6 Foot
SparkFun RedBoard Qwiic

ZED-F9R pHAT Parts SparkFun Wish List

GNSS Multi-Band Magnetic Mount Antenna - 5m (SMA)
SparkFun GPS-RTK Dead Reckoning pHAT for Raspberry Pi
Extended GPIO Female Header - 2x20 Pin (16mm/7.30mm)
SparkFun Raspberry Pi 4 Desktop Kit - 4GB
Interface Cable SMA to U.FLWRL-0

Microcontroller

If you are using the breakout board and programming in Arduino, we recommend the RedBoard Qwiic with the associated USB cable to start.

SparkFun RedBoard Qwiic
Qwiic Cable - 100mm
USB micro-B Cable - 6 Foot

Single Board Computer

If you are using the pHAT and programming in Python, we recommend the desktop kit as it includes all the parts at a minimum to get started. Note that the Raspberry Pi 4 is power hungry so make sure that you have a sufficient power supply when using the GPS remotely. An alternative is using the Raspberry Pi Zero but it's not fast as the Raspberry Pi 4.

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 make sure to get the u.FL to SMA cable if you decide to use those. 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)

Note: If you want to try different chip antennas, you can try the GNSS Antenna Evaluation Board listed below and make sure to get the u.FL to u.FL connector in the accessories. However, these antennas will not provide the full RF reception for the ZED-F9R. Additionally, if you are using a GNSS Antennas from the Evaluation Board, you will need to disconnect the inductor on the GPS breakout since they are passive antennas.

GPS/GNSS Magnetic Mount Antenna - 3m (SMA)
GPS/GNSS Embedded Antenna - 1m (SMA)
SparkFun GNSS Chip Antenna Evaluation Board

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.

Interface Cable SMA to U.FL
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.

Three Quick Tips About Using U.FL: Quick tips regarding how to connect, protect, and disconnect U.FL connectors.

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-F9R 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-F9R 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 F9R 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-F9R 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-F9R breakout board by looking for the silkscreen with the xyz axis.

axis_2

Top View with the the Axis for Reference

axis_3

Bottom View with the the Axis for Reference

Additionally, you can find the xyz axis for reference on both sides of the pHAT.

Top View with the the Axis for Reference

Bottom View with the 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.

vehicle_6

Mounting the SparkFun Dead Reckoning ZED-F9R

The only guideline here is that the SparkFun Dead Reckoning is stable within 2 degrees, and of course that the X-axis points towards the front of the car as mentioned above.

mounting_7

ZED-F9R Orientation

mounting_8

ZED-F9R pHAT's Orientation

In the image 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-F9R, 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, that prints out the module's calibration status.

Hardware Overview (Breakout)

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_9

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 ~24 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_10

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-F9R 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

leds_11

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_12

U.FL Connector

The ZED-F9R requires a good quality GPS or GNSS (preferred) antenna. A u.FL connector is provided. Note: U.FL connectors are rated for only a few mating cycles (about 30) so we recommend you set it and forget it. You may need to secure the u.FL to SMA cable depending on your application. For more information on working with u.FL connectors, we recommend checking out our tutorial about using u.FL connectors.

connector_13

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_14

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 jumpers section, you'll need to close the SPI jumper on the underside to enable SPI.

spi_15

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-F9R
RX/MOSI = RX into ZED-F9R

uart_16

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.

second_17

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_18

Broken Out Pins

There are four other pins broken out:

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-F9R can accurately calculate navigation information. Remember, it's all relative.

3d_20

9DoF Reference (Top View)

3d_21

9DoF Reference (Bottom View)

Board Dimensions

Overall, the board is 2.00"x1.70". There are 4x mounting holes by each corner of the board.

dimensions_22

Hardware Assembly (Breakout)

For this example, I used a RedBoard Qwiic and associated USB cable. Connecting the boards with Qwiic cable, the assembly is very simple. Plug a Qwiic cable between the RedBoard and SparkFun ZED-F9R. Then plugged in one of our patch antennas to the u.FL connector. If you need tips on plugging in the U.FL connector, then check out our U.FL tutorial. 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.

For secure connections, you may want to add tape or some hot glue to provide some strain relief to prevent the cable from disconnecting. When using the ZED-F9R, 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.

hardware_23

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.

secure_24

Adding a 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. The following example uses the Bluetooth Mate to connect to an Android phone's app. Depending on your personal preference, you can choose a female header or a male header for the Bluetooth Mate. We opted for the female header.

adding_25

For a low profile, we decided to use 1x6 right angle, male headers. As a result, the design of the breakout requires the top of the Bluetooth Mate to face the ZED-F9P. To ensure that there is enough space for the Bluetooth's components, make sure to insert the 1x6 right angle male header into the Bluetooth Mate's female header. Make sure to connect GND to GND, Rx to Tx, and Rx to Tx. When ready, solder the male headers to the breakout board.

solder_26

We also will need to solder a jumper wire from the 3.3V pin to the Bluetooth's VCC pin. By design, the voltage pin on the RTCM port was disconnected to avoid conflicting voltages from a device (i.e. a USB-to-Serial converter). To easily connect/disconnect, we used a M/F jumper wire. Cut the jumper wire in half, strip, and solder the wires to the respective pins.

jumper_27

jumper_28

After soldering, your setup with a correction source should look like the image below. Electrical tape was added to secure the u.FL to SMA cable. to the board.

tape_29

SparkFun u-blox Arduino Library

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 predecessors 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-F9R.

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-F9R. 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 Example Code

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 Arduino Uno), 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-F9R 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 Arduino Uno), 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-F9R has been calibrated before pulling data. If the SparkFun Dead Reckoning ZED-F9R 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.

ZED-F9P Example Folder

Once the ZED-F9R is calibrated, you will be able to use a few of the ZED-F9P examples. Note that the ZED-F9R is not able to act as a base station so a few of the examples may not apply. You'll also need to feed RTCM correction data to the ZED-F9R if you decide to utilize the RTK feature. For more information, check below.

CONNECTING THE GPS RTK TO A CORRECTION SOURCE

Hardware Overview (pHAT)

Power

Power for this board is 3.3V. Unlike the breakout board, the pHAT version pulls power from the Raspberry Pi's 3.3V pin on the 2x20 header. The Qwiic Connector's voltage pin is connected to this rail. The 3.3V pin should only be provided a clean 3.3V power signal from the Pi.

power_30

Battery

Just like the breakout board, the small metal disk in the just to the right of the ZED-F9R module 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 ~24 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_31

LEDs

Just like the breakout board, 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-F9R 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.

leds_32

Jumpers

On the top side of the board, you will notice a few jumper pads.

I²C: This three-way jumper labeled I²C connects two pull-up resistors to the I²C data lines. For general use, you can leave this jumper unmodified. If you have many I²C devices (about 7x devices, each with their own pull-up resistors), you will need to cut the jumpers
SPI: The jumper labeled SPI is open by default. Closing the jumper with solder enables the SPI data bus thus disabling the UART functions on those lines. This also disables I²C interface. USB will still function
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.

For more information, check out our tutorial on How to Work with Jumper Pads and PCB Traces.

jumpers_33

U.FL Connector

The ZED-F9R requires a good quality GPS or GNSS (preferred) antenna. A U.FL connector is provided. Note: U.FL connectors are rated for only a few mating cycles (about 30) so we recommend you set it and forget it. You may need to secure the u.FL to SMA cable depending on your application. For more information on working with u.FL connectors, we recommend checking out our tutorial about using u.FL connectors.

antenna_34

Qwiic and I²C

Note: While there is a Qwiic connector on the ZED-F9R pHAT, be aware that the board uses the hardware UART. This is due to compatibility issues with clock stretching on the Pi and the u-blox modules.

After stacking the pHAT on a Raspberry Pi, you still have access to the I²C pins (GPIO02 and GPIO03) on the top side. Alternatively, you can use the Qwiic connector to daisy chain additional I²C devices on the bus. The Qwiic ecosystem is made for fast prototyping by removing the need for soldering. All you need to do to connect additional Qwiic devices is plug a Qwiic cable into the Qwiic connector and voila! You can also access those pins from the 2x20 header.

stack_35

SPI

The pins for SPI (GPIO08, GPIO09, GPIO10, and GPIO11) are connected to the Pi if you decide to use this protocol. As mentioned in the jumper’s section, you'll need to close the SPI jumper on the top to enable SPI.

spi_36

UART

The ZED-F9R's UART1 is connected to the Pi's UART0 port (GPIO14, GPIO15). Keep in mind that the pins are tied to the MISO and MOSI pins. By default, we will be using the UART to read data from the u-blox module.

uart_37

There is a row of through holes next to the USB Type-C connector labeled for their UART functionality. 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 another computer. Note that RTCM3 data can also be sent over I2C, UART1, SPI, or USB if desired.

data_38

Note: If you look closely, the voltage pin is disconnected on the port. This is to avoid conflicting voltages from the Pi and a serial-to-UART converter. If you decide to use a Bluetooth Mate to pass RTCM correction data, make sure to wire voltage from the 3.3V pin to power it up.

USB

To connect the ZED-F9R to u-center software, you can attach a USB Type-C cable to the connector. Keep in mind that the power pin is not connected to the USB-C connector. You will need to draw power from the Qwiic connector or the Pi's 2x20 header pins.

usb_39

Wheel Tick and Direction Pins

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.

tick_40

Broken Out Pins

There are four other pins broken out:

format2

Read the u-blox Receiver Protocol Specification in the Resources and Going Further tab for more information.

broken_41

3D IMU Orientation and Reference

imu_42

imu_43

Board Dimensions

The board is slightly bigger than the breakout version. Overall, it is 65mmx56.50mm (2.56"x2.22"). There are 4x mounting holes by each corner of the board.

dimensions_44

Hardware Assembly (pHAT)

To get started with your ZED-F9R pHAT, simply plug it into the headers on the Raspberry Pi as shown below. Then connect the necessary peripherals, u.FL connector to SMA cable, and GPS/GNSS patch antenna. If you need tips on plugging in the U.FL connector, then check out our U.FL tutorial. For secure connections, you may want to add tape or some hot glue for the u.FL cable to provide some strain relief to prevent the cable from disconnecting.

phat_45

Note: If you decide that you need to use the heat sink enclosure, you will need to make sure that you are using extension headers in order to fully insert the pHAT into the Pi's 2x20 headers.

dashboard_46

Adding a RTCM Correction Source

As explained earlier for the breakout board, 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. The following example uses the Bluetooth Mate to connect to an Android phone's app. Depending on your personal preference, you can choose a female header or a male header for the Bluetooth Mate. We opted for the female header.

source_47

Note: The design of the ZED-F9R causes the attached Bluetooth Mate to take up a larger area as shown further below. You may want to consider using jumper wires to connect the Bluetooth Mate to avoid having it protrude from the pHAT. For those that want a polarized connector, you can opt to use the Molex jumper wire assembly instead of using header pins.

Jumper Wires - Connected 6" (M/F, 20 pack)
Molex Jumper 6 Wire Assembly

For a low profile, we decided to use 1x6 right angle, male headers. Depending on your application, you can use straight, male headers. As a result, the design of the breakout requires the top of the Bluetooth Mate to face the ZED-F9P. When ready, solder the male headers to the breakout board. In this case, the headers were inserted from the top and soldered on the bottom.

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Make sure to connect GND to GND, Rx to Tx, and Rx to Tx by following the silkscreen. Below is an example of what to expect before the pins are soldered. When you are finished soldering the board and cleaning the joints, make sure to stack the board back on the Raspberry Pi.

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Configure Your Pi

Note: This library assumes you are using the latest version of the Raspbian on a Raspberry Pi. If this is your first time using a Raspberry Pi, please review our tutorial on flashing an image and configuring the Pi.

The Serial peripheral is not turned on by default. There are a few methods to adjust the settings. To enable it, you will need to do the following.

Raspberry Pi Configuration via Desktop GUI

Before we download the Python package, you will need to enable your serial UART port. There are a few methods of enabling the port, but we recommend using the GUI: Raspberry Pi Start Menu > Interfaces > Raspberry Pi Configuration.

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A window will pop up with different tabs to adjust settings. What we are interested is the Interfaces Tab. Click on the tab and select Enable for Serial. If you would like to control the Raspberry Pi through the serial port terminal, you can select Enable for Serial Console. Since we are using the serial port to control another serial device, we will be selecting Disable At this point, you can enable additional interfaces depending on your project needs. Click on the OK button to save.

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We recommend restarting your Pi to ensure that the changes to take effect. Click on the Pi Start Menu > Preferences > Shutdown. Since we just need to restart, click on the Restart button.

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Shutdown

Turn Off, Restart, Log Off

raspi-config Tool via Terminal

If you prefer the old school method using a terminal, we can use raspi-config to enable it.

Run sudo raspi-config.
Use the down arrow to select 5 Interfacing Options.
Arrow down to P6 Serial.
Select no if it asks about using the login shell to be accessible over serial.
Select yes when it asks you to enable hardware serial.
Select Ok to confirm.
Use the right arrow to select the <Finish> button.
Select yes when it asks to reboot.

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The system will reboot. When it comes back up, log in and enter the following command

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ls /dev/ttyS0

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ls /dev/serial0

The Pi should respond with the port that was entered.

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/dev/ttyS0

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/dev/serial0

Note: If you are interested in testing the UART port with a serial loopback test, you can add a F/F jumper wire between Tx and Rx to echo characters back to the Pi using minicom. Just make sure to connect the pins when the Pi is powered down since the power pins are near the serial pins. First, install minicom using the following command in the terminal window. Make sure to agree to install and follow the prompts.

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sudo apt-get install minicom

Once installed, type the following in the terminal to open minicom on the /dev/ttyS0 serial port.

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sudo minicom -D /dev/ttyS0

With the jumper connected, any characters entered will loop back in the window. Sweet, we know that the serial port is working so you can remove the jumper at this point.

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When finished, type CTRL+A followed by X to exit minicom.

U-Blox Python Package

Python Versions and Installing PIP

There are also 2 commonly used Python versions. Even after Python 3 came out many people continued to use 2.7 for many years. Part of the reason is that Python 3 improved on some things and in the process made it not backwards compatible. We recommend using Python 3 since Python 2 has reached its end of life. To see what version of Python your Pi is using, open a command line and type each of the following commands individually to check.

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python --version
pip --version

If you are not using Python 3, then we'll need to open the *.bashrc file and add an alias.

First, you will need to update the python installation package by running the following command to install pip for Python 3. Execute the following commands.

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sudo apt-get install python3-pip

Type the following command to open the file.

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nano ~/.bashrc

Then add the following lines at the end. That should tell the computer whenever you want to run python to look for the file located at /usr/bin/python3.

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alias python='/usr/bin/python3'
alias pip=pip3

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To exit nano type CTRL + X and then hit Y when it asks you if you want to save and then ENTER. You can now either reboot or type the following to force the Pi to run the *.bashrc file again.

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source ~/.bashrc

Once adjusted, type the following command to ensure that pip is up to date.

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python -m pip install --upgrade pip

Qwiic Python Package

We will also need to install the Qwiic Python libraries. This will automatically download a folder containing all the Qwiic_Py files and dependencies to your Raspberry Pi. Run the following command to automatically install the modules for SparkFun devices. Note that while the u-Blox Python package is included in the Qwiic_Py, the pHAT uses the hardware UART instead of I²C bus. To ensure that you are installing to the correct path for Python 3, make sure that you use pip3.

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sudo pip3 install sparkfun-qwiic

Tip: If you need to uninstall the library and start from scratch, simply use the uninstall with the command:

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sudo pip3 uninstall sparkfun-qwiic

Python Example Code

We will be using the example in the uBlox GPS Py GitHub repo. This should automatically install the package if you installed Qwiic_Py. Feel free to check out the associated ReadtheDocs as well!

GITHUB: QWIIC UBLOX GPS PY

Connecting the GPS-RTK to a Correction Source

Note: To connect the GPS-RTK to a correction source, we recommend checking out the GPS-RTK and GPS-RTK2 hookup guides. We recommend reading up on these tutorials for more information should you decide to use a different correction source that fits your application.

What is GPS RTK? - SEPTEMBER 14, 2018: Learn about the latest generation of GPS and GNSS receivers to get 14mm positional accuracy!

GPS-RTK Hookup Guide - SEPTEMBER 13, 2018: Find out where you are! Use this easy hook-up guide to get up and running with the SparkFun high precision GPS-RTK NEO-M8P-2 breakout board.

GPS-RTK2 Hookup Guide - JANUARY 14, 2019: Get precision down to the diameter of a dime with the new ZED-F9P from u-blox.

Resources and Going Further

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: