The BME280 is one of the easiest sensors to integrate into Home Assistant for live temperature, humidity, and pressure monitoring. In this guide, we show you how to install the sensor, flash the ESP32, configure MQTT, and view the readings inside Home Assistant.

This example uses standard Arduino libraries, MQTT, and Home Assistant’s built-in MQTT integration.

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1. What You Need

• ESP32 development board
• BME280 (I²C version)
• 4 jumper wires
• Home Assistant running on your network
• MQTT broker (built-in Mosquitto or external)
• Arduino IDE with ESP32 board support

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2. Wiring the ESP32 to BME280

BME280	ESP32
VIN	3.3V
GND	GND
SCL	GPIO 22
SDA	GPIO 21

This wiring matches the ESP32’s default I²C pins.

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3. Installing Required Arduino Libraries

Open Arduino IDE → Tools → Manage Libraries and install:

• Adafruit BME280
• Adafruit Unified Sensor
• PubSubClient
• ESP32 WiFi (already included)

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4. ESP32 Code (Ready to Flash)

Below is the full working sketch.
Important: Replace WiFi and MQTT credentials with yours.

#include <WiFi.h>
#include <PubSubClient.h>
#include <Wire.h>
#include <Adafruit_BME280.h>

#define WIFI_SSID "wifi"
#define WIFI_PASS "password"
#define MQTT_SERVER "192.168.0.10"   // Home Assistant IP
#define MQTT_PORT 1883
#define MQTT_USER "user"
#define MQTT_PASS "password"

Adafruit_BME280 bme;
WiFiClient espClient;
PubSubClient client(espClient);

void setup() {
  Serial.begin(115200);
  WiFi.begin(WIFI_SSID, WIFI_PASS);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("\nWiFi connected");
  
  client.setServer(MQTT_SERVER, MQTT_PORT);

  if (!bme.begin(0x76)) {
    Serial.println("BME280 not found!");
    while (1);
  }
}

void loop() {
  if (!client.connected()) {
    reconnect();
  }
  client.loop();

  float temp = bme.readTemperature();
  float hum = bme.readHumidity();
  float press = bme.readPressure();
  float alt = bme.readAltitude(1013.25);

  char payload[100];
  snprintf(payload, sizeof(payload), "{\"temperature\":%.2f,\"humidity\":%.2f,\"Pressure\":%.2f,\"Altitude\":%.2f}",
           temp, hum, press, alt);

  client.publish("home/livingroom/sensor", payload);

  delay(10000);  // every 10 seconds
}

void reconnect() {
  while (!client.connected()) {
    if (client.connect("esp32_livingroom", MQTT_USER, MQTT_PASS)) {
      Serial.println("Connected to MQTT");
    } else {
      delay(2000);
    }
  }
}

This publishes a JSON payload every 10 seconds to:

home/livingroom/sensor

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5. Configure Home Assistant

A. Add MQTT Integration (if not already)

Home Assistant → Settings → Devices & Services → Add Integration → MQTT

Set your broker IP, username, and password.

B. Add MQTT Sensor Definitions

Edit configuration.yaml:

sensor:
  - platform: mqtt
    name: "Living Room Temperature"
    state_topic: "home/livingroom/sensor"
    unit_of_measurement: "°C"
    value_template: "{{ value_json.temperature }}"

  - platform: mqtt
    name: "Living Room Humidity"
    state_topic: "home/livingroom/sensor"
    unit_of_measurement: "%"
    value_template: "{{ value_json.humidity }}"

  - platform: mqtt
    name: "Living Room Pressure"
    unit_of_measurement: "Pa"
    state_topic: "home/livingroom/sensor"
    value_template: "{{ value_json.Pressure }}"

  - platform: mqtt
    name: "Living Room Altitude"
    unit_of_measurement: "m"
    state_topic: "home/livingroom/sensor"
    value_template: "{{ value_json.Altitude }}"

Save → Restart Home Assistant.

You will now see 4 new sensors.

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6. View Your Sensor in Home Assistant

Go to:

Overview → Add Card → Sensor

Choose your new sensors:

• Living Room Temperature
• Living Room Humidity
• Living Room Pressure
• Living Room Altitude

You now have a live dashboard.

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7. Troubleshooting

BME280 Not Found

• Check wiring
• Confirm address: most boards use 0x76, some use 0x77

No MQTT Data

• Check broker IP
• Check username/password
• Use MQTT Explorer to verify messages

WiFi Fails to Connect

• Ensure 2.4 GHz WiFi is enabled
• ESP32 cannot connect to WPA3-only networks

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8. Final Notes

This setup works perfectly for:

• Multiple rooms
• Outdoor sensors
• Climate dashboards
• Automations (fans, AC, HVAC)

The ESP32 + BME280 combo is stable, accurate, and cheap—ideal for Home Assistant installations.