This Python script implements the DiashowDL Sensor Interface on single-board computers with either a BME680 or SCD30 I2C sensor. The Diashow App discovers this node via UDP broadcast and polls it for environment data over HTTPS.

• Single-board computer with I2C support (see table above)
• BME680 breakout (temperature, humidity, pressure, IAQ) or SCD30 module (temperature, humidity, CO2)

Enable I2C on the Pi:

sudo raspi-config   # Interface Options > I2C > Enable

# Create virtual environment
python3 -m venv venv
source venv/bin/activate

# Install dependencies
pip install -r requirements.txt

# Copy and edit configuration
cp config.example.json config.json
# Edit config.json: set api_key, sensor type, and i2c_bus for your board

Generate a self-signed certificate for HTTPS:

openssl req -x509 -nodes -days 3650 -newkey rsa:2048 \
  -keyout key.pem -out cert.pem -subj "/CN=DiashowSensor"

The generated cert.pem and key.pem are referenced in config.json and excluded from Git.

source venv/bin/activate
python3 sensor_node.py

curl -k -H "X-Api-Key: your-sensor-api-key" https://localhost:9132/

Create /etc/systemd/system/diashow-sensor.service:

[Unit]
Description=DiashowDL Sensor Node
After=network-online.target
Wants=network-online.target

[Service]
Type=simple
User=pi
WorkingDirectory=/home/pi/diashow-sensor
ExecStart=/home/pi/diashow-sensor/venv/bin/python3 sensor_node.py
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target

Then enable and start:

sudo systemctl daemon-reload
sudo systemctl enable diashow-sensor
sudo systemctl start diashow-sensor

The BME680 IAQ score is computed using a rolling-baseline algorithm (ported from dart_periphery). It maintains a window of 50 gas resistance readings to establish a baseline, then scores gas (75%) and humidity (25%) relative to their baselines. The score stabilizes after approximately 50 readings.