ESP32 IoT Weather Station: BME280 Arduino Code

BuildWhat You Will Build

GoalsLearning Objectives

• Wire a BME280 sensor over I2C using common Arduino-ESP32 GPIO21/GPIO22 defaults.
• Detect whether the BME280 responds at 0x76 or 0x77.
• Read temperature, humidity, and pressure and print clear labeled Serial Monitor values.
• Interpret local pressure in hPa without confusing it with sea-level adjusted weather reports.
• Identify placement-induced errors from heat, breath, sunlight, enclosures, and poor airflow.
• Share the I2C bus with an optional SSD1306 OLED later when addresses do not conflict.
• Extend reliable local sensor data into MQTT, logging, or a Wi-Fi dashboard after the core reading works.

PartsComponents List

• PartESP32 DevKit boardMain controller with Wi-Fi
• PartBME280 sensor moduleTemperature, humidity, and pressure sensor
• PartSSD1306 OLED displayOptional local display for readings
• PartBreadboard and jumper wiresFor safe low-voltage prototyping
• PartUSB data cableProgramming and bench power

PartsBill of Materials

🔗Wiring

Wire the BME280 first: VCC to 3.3 V, GND to GND, SDA to GPIO21, and SCL to GPIO22. Verify temperature, humidity, pressure, and the detected 0x76 or 0x77 I2C address in Serial Monitor before adding an optional OLED, MQTT feed, or Wi-Fi dashboard.

1. 1

   Unplug USB before wiring the breadboard.

2. 2

   Connect the BME280 breakout VCC to 3.3 V unless that exact breakout documentation says another supply is safe.

3. 3

   Connect BME280 GND to ESP32 GND.

4. 4

   Connect BME280 SDA to GPIO21 and SCL to GPIO22, the common Arduino-ESP32 I2C defaults.

5. 5

   Reconnect USB, upload the core sketch, and open Serial Monitor at 115200 baud.

6. 6

   If you later add an OLED, connect its SDA and SCL to the same I2C bus, confirm its address, and keep signals ESP32-safe.

GPIO Mapping

Circuit Explanation

Engineering Explanation

⌨️Code

Copy into Arduino IDE. Install any libraries noted in the component guides first.

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

Adafruit_BME280 bme;

bool beginBME280() {
  if (bme.begin(0x76)) {
    Serial.println("BME280 found at I2C address 0x76");
    return true;
  }

  if (bme.begin(0x77)) {
    Serial.println("BME280 found at I2C address 0x77");
    return true;
  }

  return false;
}

void setup() {
  Serial.begin(115200);
  delay(200);

  Serial.println("ESP32 BME280 weather station");
  if (!beginBME280()) {
    Serial.println("BME280 not found at 0x76 or 0x77.");
    Serial.println("Check 3.3 V, GND, SDA=GPIO21, SCL=GPIO22, and module address.");
    while (true) delay(100);
  }

  Serial.println("Reading temperature, humidity, and pressure every 2 seconds");
}

void loop() {
  float tempC = bme.readTemperature();
  float humidity = bme.readHumidity();
  float pressureHpa = bme.readPressure() / 100.0F;

  Serial.print("Temperature C: ");
  Serial.print(tempC, 1);
  Serial.print(" | Humidity %: ");
  Serial.print(humidity, 1);
  Serial.print(" | Pressure hPa: ");
  Serial.println(pressureHpa, 1);

  delay(2000);
}

Code Explanation

PhotosBuild Photos

• Photo Breadboard overviewShow the ESP32, BME280 placement, USB connection, and 3.3 V/GND rails clearly.
• Photo Close-up wiringCapture SDA on GPIO21, SCL on GPIO22, 3.3 V, and GND so beginners can compare their build.
• Photo Working outputShow Serial Monitor with temperature, humidity, pressure hPa, and the detected BME280 address.