GPS-RTK Hookup Guide

Contributors: Nate

SparkFun u-blox Arduino Library

The GPS-RTK Arduino library enables the reading of NMEA data over I2C as well as sending binary UBX configuration commands over I2C. This is helpful for configuring advanced modules like the NEO-M8P-2.

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:

Once you have the library installed checkout the various examples.

• Example1: Read NMEA sentences over I²C using u-blox module SAM-M8Q, NEO-M8P, etc
• Example2: Parse NMEA sentences using MicroNMEA library. This example also demonstrates how to overwrite the processNMEA function so that you can direct the incoming NMEA characters from the u-blox module to any library, display, radio, etc that you prefer.
• Example3: Get latitude, longitude, altitude, and satellites in view (SIV). This example also demonstrates how to turn off NMEA messages being sent out of the I²C port. You’ll still see NMEA on UART1 and USB, but not on I²C. Using only UBX binary messages helps reduce I²C traffic and is a much lighter weight protocol.
• Example4: Displays what type of a fix you have the two most common being none and a full 3D fix. This sketch also shows how to find out if you have an RTK fix and what type (floating vs. fixed).
• Example5: Shows how to get the current speed, heading, and dilution of precision.
• Example6: Demonstrates how to increase the output rate from the default 1 per second to many per second; up to 30Hz on some modules!
• Example7: Older modules like the SAM-M8Q utilize an older protocol (version 18) whereas the newer modules like the ZED-F9P depricate some commands using the latest protocol (version 27). This sketch shows how to query the module to get the protocol version.
• Example8: u-blox modules use I²C address 0x42 but this is configurable via software. This sketch will allow you to change the module’s I²C address.
• Example9: Altitude is not a simple measurement. This sketch shows how to get both the ellipsoid based altitude and the MSL (mean sea level) based altitude readings.
• Example10: Sometimes you just need to do a hard reset of the hardware. This sketch shows how to set your u-blox module back to factory default settings.
• NEO-M8P: Examples specific for the NEO-M8P.
  • NEO-M8P Example1: Send UBX binary commands to enable RTCM sentences on U-blox NEO-M8P-2 module. This example is one of the steps required to setup the NEO-M8P as a base station. For more information have a look at the u-blox manual for setting up an RTK link.
  • NEO-M8P Example2: This example extends the previous example sending all the commands to the NEO-M8P-2 to have it operate as a base. Additionally the processRTCM function is exposed. This allows the user to overwrite the function to direct the RTCM bytes to whatever connection the user would like (radio, serial, etc).
  • NEO-M8P Example3: This is the same example as NEO-M8P's Example2. However, the data is sent to a serial LCD via I²C.
• ZED-F9P: Examples specific for the ZED-F9P.
  • ZED-F9P Example1: This module is capable of high precision solutions. This sketch shows how to inspect the accuracy of the solution. It’s fun to watch our location accuracy drop into the millimeter scale.
  • ZED-F9P Example2: The ZED-F9P uses a new u-blox configuration system of VALGET/VALSET/VALDEL. This sketch demonstrates the basics of these methods.
  • ZED-F9P Example3: Setting up the ZED-F9P as a base station and outputting RTCM data.
  • ZED-F9P Example4: This is the same example as ZED-F9P's Example3. However, the data is sent to a serial LCD via I²C.

This SparkFun u-blox library really focuses on I²C because it's faster than serial and supports daisy-chaining. The library also uses the UBX protocol because it requires far less overhead than NMEA parsing and does not have the precision limitations that NMEA has.