MQTT Temperature and Humidity Sensor

Arduino code for periodically publishing temperature and humidity measurements to an MQTT broker.

Hardware

• Arduino-compatible board with WiFi connectivity. For this project, I used the FeatherS3 development board
• BME280 Temperature, Humidity, and Pressure Sensor. Adafruit offers a breakout board which easily connects to the STEMMA QT connector on the FeatherS3 board
• STEMMA QT cable
• Lithium Polymer Battery with JST connector

Libraries

The following libraries should be added to the Arduino IDE using the library manager.

• Adafruit_BME280_Library
• MQTT
• ArduinoJson

Configuration

Create a file called "secrets.h" and set the following constants. Note that "secrets.h" is ignored in the .gitignore file to avoid accidentally checking it in.

• WIFI_SSID - the SSID of the WiFi network to connect to.
• WIFI_PASSWORD - the password for the WiFi network.
• MQTT_CLIENT_ID - the client ID for connecting to the MQTT broker.
• MQTT_BROKER - the hostname or IP address (e.g., IPAddress(192, 168, 1, 1)) of the MQTT broker.
• TEMP_TOPIC - the name of the topic to publish temperature messages.
• HUMIDITY_TOPIC - the name of the topic to publish humidity messages.
• LOOP_DELAY - integer representing the delay in milliseconds at the end of loop().

Example Output

After opening the serial monitor, you should see something similar to the following if everything works as expected:

Initializing BME280 sensor...OK
Connecting to Wi-Fi.....OK
Connecting to MQTT broker...OK
PUBLISH home/office/temperature - {"time":4043,"temperature":24.79000092} - OK
PUBLISH home/office/humidity - {"time":4045,"humidity":33.27246094} - OK

TODO

• Reconnect to WiFi and MQTT on disconnect
• Add username/password authentication for MQTT
• Add TLS support for MQTT