Introduction
Off the shelf hardware is used to demonstrate integrating a GNSS receiver with Digi International’s LTE-M/NB-IoT cellular smart modem. The project utilizes the XB3-C-A2-UT-001 mounted in an XBIB-U-DEV eval board wired to a Mikroelektronika GNSS 5 Click board. MicroPython example code is provided for the XBee3 smart modem to communicate with the GNSS 5 Click receiver over UART and query position data. Mikroelektronika’s GNSS 5 Click™ board uses U-blox’s NEO-M8N GNSS receiver module.
Hardware Requirements
- XB3-C-A2-UT-001 Digi XBee3 LTE-M/NB-IoT Cellular Smart Modem at Digi-Key
- Mikroelektronika GNSS 5 Click™ board at Digi-Key
Accessories
- Digi International XBIB-U-DEV eval board at Digi-Key (note: male pin headers soldered to XBIB-U-DEV board 20 pin header to facilitate wiring)
Supplier Documentation
- Digi International XBee3 Cellular LTE-M/NB-IoT User Guide
- Digi International Digi MicroPython Programming Guide
- Digi International XBIB-U-DEV Reference Guide
- Digi International XBIB-U-DEV Schematic
- Mikroelektronika GNSS 5 Click™ board
- u-blox M8 Receiver Description including Protocol Specification
- u-blox NEO-M8 Resources and Documentation
- u-blox u-center GNSS evaluation software for Windows
:
Hardware Setup
GNSS 5 Click Board
| 1 - | 16 - |
|---|---|
| 2 - | 15 - |
| 3 - | 14 - RX |
| 4 - | 13 - TX |
| 5 - | 12 - |
| 6 - | 11 - |
| 7 - | 10 - |
| 8 - | 9 - |
note: powered by USB
XB3 20 pin header
| 1 - | 20 - |
|---|---|
| 2 - | 19 - |
| 3 - | 18 - |
| 4 - RX | 17 - |
| 5 - | 16 - |
| 6 - | 15 - |
| 7 - | 14 - |
| 8 - | 13 - |
| 9 - | 12 - |
| 10 - | 11 - TX |
Wiring Diagram
Example Code
Description
MicroPython code that runs on a Xbee 3 cellular module connected to a GNSS 5 Click board over UART. The example code configures the Xbee UART for 9600 baud and the u-blox M8 module for UBX communication protocol over UART at 9600 baud. The Xbee then communicates with the M8 module to check GNSS position fix and read longitude / latitude. This is repeated in a continuous loop.
u-blox NEO-M8N Configuration Settings and Commands Background
The u-blox M8 GNSS receiver supports both NMEA and u-blox’s proprietary UBX communication protocols. In this code example UBX protocol is used because it is compact, modular and efficient to implement. The UBX protocol is fully described in the u-blox 8 / u-blox M8 Receiver Description - Manual as well as detailed specifications on each UBX command. The UBX-CFG-PRT command is configured to set UART baud rate to 9600 and output only UBX data. The UBX-NAV-STATUS command is used to check for GNSS position fix and UBX-NAV-POSLLH to read latitude / longitude.
u-blox | u-center GNSS evaluation software for Windows
u-blox’s u‑center GNSS evaluation software is a great tool for evaluation, performance analysis and configuration of u‑blox GNSS receivers. During development of the example code, “Messages View” and “Binary Console” within the u-center tool were used to determine the binary data for the UBX commands used. Below screen shot shows the UBX-CFG-PRT command and the binary data.
