This project had two main goals:
- Learn more about MQTT for IoT projects
- Get used to the ESP32 development framework
To use MQTT, I decided to use a Raspberry Pi as the broker using Mosquitto. Once the broker was set up, I worked on the ESP32 side of the project. Doing this using the Arduino Framework would have been much easier, but I wanted to use the ESP-IDF to understand better how things worked.
The first step was to adapt my AHT10 temperature and humidity driver from an ATMega328 to work with the ESP32. After this, I used the ESP-IDF WiFi and MQTT examples as base, and was able to connect the ESP32 to the broker and publish the temperature and humidity data. To display the data I used the Paho Javascript library and used websockets to subscribe to the different topics.
The result is a simple website that shows the temperature and humidity readings in real time and a graph with the day's history.
The data used to create the graph comes from a .csv file created with a Python script (mqtt_read.py) running on the Raspberry Pi. The script reads the sensors' values and every two minutes it appends the data to a .csv file named after the date. Each day a new file is created for each sensor.
