SparkFun GPS-RTK Dead Reckoning pHAT for Raspberry Pi

The SparkFun ZED-F9R GPS pHAT is a high precision, sensor fusion GPS board with equally impressive configuration options and takes advantage of u-blox's Automotive Dead Reckoning (ADR) technology. The ZED-F9R module provides a highly accurate and continuous position by fusing a 3D IMU sensor, wheel ticks, a vehicle dynamics model, correction data, and GNSS measurements.

The ZED-F9R module is a 184-channel u-blox F9 engine GNSS receiver, meaning it can receive signals from the GPS, GLONASS, Galileo, and BeiDou constellations with ~0.2 meter accuracy! That's right, such accuracy can be achieved with an RTK navigation solution when used with a correction source. Note that the ZED-F9R can only operate as a rover, so you will need to connect to a base station. The module supports concurrent reception of four GNSS systems. The combination of GNSS and integrated 3D sensor measurements on the ZED-F9R provide accurate, real-time positioning rates of up to 30Hz.

Compared to other GPS modules, this pHAT maximizes position accuracy in dense cities or covered areas. Even under poor signal conditions, continuous positioning is provided in urban environments and is also available during complete signal loss (e.g. short tunnels and parking garages). The ZED-F9R is the ultimate solution for autonomous robotic applications that require accurate positioning under challenging conditions.

This u-blox receiver supports a few serial protocols. By default, we chose to use the Raspberry Pi's serial UART to communicate with the module. With pre-soldered headers, no soldering is required to stack the pHAT on a Raspberry Pi, NVIDIA Jetson Nano, Google Coral, or any single board computer with the 2x20 form factor. We have also broken out a few 0.1"-spaced pins from the u-blox receiver. A Qwiic connector is also added in case you need to connect a Qwiic enabled device.

U-blox based GPS products are configurable using the popular, but dense, windows program called u-center. Plenty of different functions can be configured on the ZED-F9R: baud rates, update rates, geofencing, spoofing detection, external interrupts, SBAS/D-GPS, etc.

The SparkFun ZED-F9R GPS pHAT is also equipped with an on-board rechargeable battery that provides power to the RTC on the ZED-F9R. This reduces the time-to-first fix from a cold start (~24s) to a hot start (~2s). The battery will maintain RTC and GNSS orbit data without being connected to power for plenty of time.

Features

• 1x Qwiic Connector
• Integrated U.FL connector for use with antenna of your choice
• Concurrent reception of GPS, GLONASS, Galileo and BeiDou
• 184-Channel GNSS Receiver
• Receives both L1C/A and L2C bands
• Horizontal Position Accuracy:
  • 0.20m with RTK
• Max Navigation Rate: Up to 30Hz
• Time to First Fix
  • Cold: 24s
  • Hot: 2s
• Operational Limits
  • Max G: ≤4G
  • Max Altitude: 50km (31 miles)
  • Max Velocity: 500m/s (1118mph)
• Velocity Accuracy: 0.5m/s
• Heading Accuracy: 0.2 degrees
• Built-In Accelerometer and Gyroscope
• Time Pulse Accuracy: 30ns
• Voltage: 5V or 3.3V but all logic is 3.3V
  • Current: ~85mA to ~130mA (varies with constellations and tracking state)
• Software Configurable
  • Geofencing
  • Odometer
  • Spoofing Detection
  • External Interrupt
  • Pin Control
  • Low Power Mode
  • Many others!
• Supports NMEA, UBX, and RTCM protocols over UART

Related Documents

• Schematic
• Eagle Files
• Board Dimensions
• ZED-F9R Datasheet