bmp280

Overview

The bmp280 node reads temperature and barometric pressure from the Bosch BMP280 sensor via I2C. It also calculates altitude from the pressure reading. This sensor is widely used in weather stations, indoor navigation, drone altitude hold, and environmental monitoring systems.

Wiring (I2C)

sudo raspi-config
# Interface Options → I2C → Enable

# Verify sensor detected:
i2cdetect -y 1
# Should show 76 or 77

Properties

Output

{
  "payload": {
    "temperature": 22.35,
    "pressure": 1012.8,
    "altitude": 3.7
  },
  "temperature": 22.35,
  "pressure": 1012.8,
  "altitude": 3.7,
  "timestamp": 1640000000000
}

Example: Weather Station with Altitude

Build a weather station that tracks pressure trends and calculates altitude above sea level.

// Function node: Pressure trend and altitude analysis
var pressure = msg.pressure;
var history = flow.get('pressureHistory') || [];

history.push({
    pressure: pressure,
    time: Date.now()
});

// Keep last 3 hours of readings
var threeHoursAgo = Date.now() - (3 * 60 * 60 * 1000);
history = history.filter(r => r.time > threeHoursAgo);
flow.set('pressureHistory', history);

// Calculate trend
var trend = "stable";
if (history.length > 1) {
    var oldest = history[0].pressure;
    var change = pressure - oldest;
    if (change > 1.5) trend = "rising";
    else if (change < -1.5) trend = "falling";
}

// Forecast based on pressure trend
var forecast = "No change expected";
if (trend === "rising") forecast = "Weather improving";
if (trend === "falling") forecast = "Possible rain ahead";

msg.payload = {
    temperature: msg.temperature,
    pressure: pressure,
    altitude: msg.altitude,
    trend: trend,
    forecast: forecast
};

return msg;

Example: Altitude Data Logger

Log altitude changes for hiking or drone flight recording.

// Function node: Track altitude changes
var altitude = msg.altitude;
var prev = flow.get('lastAltitude') || altitude;
var maxAlt = flow.get('maxAltitude') || altitude;
var minAlt = flow.get('minAltitude') || altitude;

maxAlt = Math.max(maxAlt, altitude);
minAlt = Math.min(minAlt, altitude);
flow.set('lastAltitude', altitude);
flow.set('maxAltitude', maxAlt);
flow.set('minAltitude', minAlt);

msg.payload = {
    current: altitude.toFixed(1),
    change: (altitude - prev).toFixed(2),
    max: maxAlt.toFixed(1),
    min: minAlt.toFixed(1),
    totalClimb: (maxAlt - minAlt).toFixed(1)
};

return msg;

Use Cases