What is it?

This module uses the worlds first GPS (GNSS) receiver with built in Untethered Dead Reckoning (UDR), the U-blox NEO-M8U. This device provides professional grade accuracy, and allows the module to continue navigating without any GPS signal, and allows increased accuracy when signal conditions are poor.

The below image shows an example of the difference the UDR system makes during poor signal conditions;

This module breaks out the functionality of U-blox module and contains all of the passives required in order to get it operating. All of the necessary signals can be connected to the Raspberry Pi header via solder jumpers. Normal solder pads are also provided so you are not forced to use a Raspberry Pi header.

This board also includes a backup coin cell battery holder (no battery provided due to shipping restrictions) to store the latest navigation information. This not only reduces the time to first fix, but combined with the dead reckoning capability means that the device can start navigating immediately on power up, even in tunnels or covered car parks!

The module also contains a full USB host and will enumerate as a COM port on computers with a suitable driver (see the U-blox website for information.

The number of configuration options of the NEO-M8U is incredible! Geofencing, variable I2C address, variable update rates, etc. This module even has four communications ports: USB (which enumerates as a COM port), UART (with 3.3V TTL), I2C, and SPI.

Libraries?

If you are using Python I have written a package for decoding UBX messages from uBlox modules. Simply pip install ubxtranslator and visit the github repo for more info.

How do I use it?

For schematics and detailed information on how to use this module please see the github repo and the wiki pages.

Specs

• Supply voltage: 5V via the header pins
• Current requirement: max 67mA, typical 29mA
• Digital IO voltage: 3V3
• Dimensions: 65mm x 36.5mm
• Time to first fix: cold start 26 to 57s, hot start 1.5s
• Horizontal position accuracy: 2.5m
• Velocity accuracy: 0.5m/s
• Heading accuracy: 1 degree
• Position error during signal loss: 10% distance travelled (<60sec signal loss)
• Operational limits: dynamics ≤ 4 g, altitude 50,000 m, velocity 500 m/s
• Supported constellations: BeiDou, Galileo, GLONASS, GPS / QZSS
• Concurrent constellations: 3

Interfaces

NB All interfaces are selectable via jumpers and broken out to wire pads.

• I2C / TWI / DDC (Pi I2C bus 1) default
• 3.3V UART (Pi '/dev/serial0')
• SPI (Pi SPI bus 0)
• USB (via micro USB connector, no connection to the Pi header)
• External interrupt (Pi GPIO 11)
• Pulse per second (Pi GPIO 13)
• Reset (Pi GPIO 15)

Indicator LED's

• 5V power (green)
• USB active (red)
• Pulse per second (blue - software configurable period)

Optional extras

The board comes fully assembled, however you can order the following additional extras;

1. Populated 40 pin stackable header suit. Raspberry Pi.

2. A uFl to SMA (bulk head) pig tail. For connection to external antennas with SMA termination.

3. If you want to squeeze the most out of this module you will need a high quality antenna and the Taoglas AA.170.301111 is a great match. This antenna has some impressive stats, see the datasheet for more information.