Real time data logging to csv and concurrent plotting with matplotlib, creating an mqtt client to listen to the specified topic on a specified mqtt broker/host.

Logger is under raspi/app_logger/app.py. For example:

python raspi/app_logger/app.py -t # -d -h 192.168.0.17 -g 

i.e. "all topics ("#"), for mqtt broker on host 192.168.0.17, include plotting (-g)

Seperate threads and callbacks are made for plotting and writing to the datafile

• log_worker empties the data-to-log queue every 2 seconds
• plotter.update is the matplotlib.animate.funcanimation function that updates the graph every provided interval (also has a queue to process data)

Example Video:

Esp32 code for sensor and mqtt client/publishing is also included.

Setting Up the ESP32 sensor

A BME temperature sensor is used over Two-Wire/I2C.

TODO - wiring diagram

Setting up the RasPi/MQTT Broker

On local machine:

# use SSH from a terminal to get into the Pi server
ssh pi@raspberrypi.local 
# ... enter user/pass ...

In a server terminal (or after SSHing in):

# print IP address (should match the one in `secrets.h`)
hostname -I 
# ...
# check the `mosquitto` status:
systemctl status mosquitto.service 
# ... if status is running try:
mosquitto_pub -d -t inTopic -m "ON" 
# which should turn the builtin on the ESP32 ON if it is OFF

If necessary restart the mosquitto service with sudo systemctl restart mosquitto

If we want to see the outTopic responses from the ESP32 we can open up another terminal on the MQTT broker and subscripe to this topic e.g. mosquitto_sub -d -t outTopic Or to subscribe to all topics do: mosquitto_sub -d -t "#"

Notes/Gotchas

• the mosquitto broker has to be configured to accept anonymous connections (disabled by default)
• put the ESP32 in "flash" mode by (1) pressing and holding BOOT (2) pressing and releasing ENABLE (3) releasing BOOT

Code Description - ESP32

Overview:

• publishes values to topic as e.g. GATEWAY_ID/DEVICE_ID/temperature/32.0
• was implemented using C style strings, should probably be refactored to smart pointers and std library strings
• currently implemented publishing from a bme280 temperature and humidity sensor (via Adafruit libary)

mqttHelper

Establishes a connection to an MQTT broker, subscribes to specific topics, and publishes sensor data to MQTT topics. including potential buffer overflow issues when dealing with large float values, minimal error handling, and limited documentation. Additionally, it lacks configurability for MQTT client parameters, making it less flexible for different MQTT broker setups

Need to add more error handling and confirugability for different MQTT client parameters (e.g. name, etc).

wifiHelper

Sets up wifi with the WiFi.h library.