Digi Xbee3 Cellular to GNSS 5 Click sensor with MicroPython

ScottRaeker · March 3, 2021, 10:25pm

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

github.com

eewiki/Xbee3-MicroPython/blob/master/samples/gnss5click.py

# Micropython code example for Digi International Xbee3
# cellular module interface to u-blox NEO-M8N GNSS receiver
# based Mikroelektronika GNSS 5 Click board   
#
# Wiring Diagram:
# XBee ->  GNSS 5 Click
#  11  TX  14 RX 
#   4  RX  13 TX 
# note: GNSS 5 powered by USB

from machine import I2C, UART
from time import sleep
import ustruct
# use UART interface to GNSS 5


# configure u-blox NEO-M8N uart for 9600 baud and UBX output mode
def config_M8():
  u = UART(1, 9600)
  u.init(9600, bits=8, parity=None, stop=1)

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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.