Bosch’s BME280 is a precision sensor used in a myriad of applications ranging from weather monitoring to gaming controls to altitude measurement where accuracy of just a few feet is required.

This sensor is simple to use, comes pre-calibrated, and requires no additional components, so you can start measuring relative humidity, temperature, barometric pressure, and altitude in no time. 

So, let’s get acquainted with the BME280, which we have heard a lot about.

BME280 Capabilities

Hardware Overview

BME280 IC

At the core of the module is the next-generation digital temperature, humidity, and pressure sensor from Bosch – BME280. It is the successor to sensors such as the BMP180, BMP085 and BMP183.

Power

The module includes an on-board LM6206 3.3V regulator and I2C Voltage Level Translator, so you can use it with a 3.3V or 5V logic microcontroller like Arduino without worry.

The BME280 consumes less than 1mA during measurements and only 5μA when idle. Because of its low power consumption, it can be used in battery-powered devices such as handsets, GPS modules, and watches.

I2C Interface

The BME280 module communicates via I2C and supports two I2C addresses, 0x76 and 0x77, allowing up to two sensors to be used on the same bus.

The module’s default I2C address is 0x76_HEX, which can be easily changed to 0x77_HEX using the provided solder jumper.

To change the i2c address to 0x77, cut the trace between the middle and left copper pads with a sharp knife. Then, add a solder blob between the middle and right copper pads to short them.

Technical Specifications

Here are the specifications:

For more information, please refer to the datasheet below.

BME280 Sensor Pinout

The BME280 module has only 4 pins that interface it to the outside world. The connections are as follows:

VIN supplies power to the module. Connect any voltage between 3.3V and 5V to this pin.

GND is the ground pin.

SCL is a serial clock pin for the I2C interface.

SDA is a serial data pin for the I2C interface.

Wiring a BME280 Module to an Arduino

Let’s hook the BME280 module to the Arduino.

Connections are straightforward. Begin by connecting the VCC pin to the Arduino’s 5V output and the GND pin to ground.

Now we are left with the pins that are used for I2C communication. Note that each Arduino Board has different I2C pins that must be connected correctly.  On Arduino boards with the R3 layout, the SDA (data line) and SCL (clock line) are on the pin headers close to the AREF pin. They are also referred to as A5 (SCL) and A4 (SDA).

The following table lists the pin connections:

The diagram below shows how to connect everything.

Installing Necessary libraries

To begin reading sensor data, you must first install the Adafruit BME280 Library. It is available from the Arduino library manager.

To install the library, navigate to Sketch > Include Library > Manage Libraries… Wait for the Library Manager to download the libraries index and update the list of installed libraries.

Filter your search by entering ‘bme280’. Look for the Adafruit BME280 Library by Adafruit. Click on that entry and then choose Install.

The BME280 sensor library makes use of the Adafruit Sensor support backend. So, look for Adafruit Unified Sensor and install it as well (you may have to scroll a bit).

Arduino Example Code

Here is a simple program that reads the temperature, relative humidity, pressure, and approx. altitude from the BME280 module and prints them on the serial monitor.

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

#define SEALEVELPRESSURE_HPA (1013.25)

Adafruit_BME280 bme;

void setup() {
	Serial.begin(9600);

	if (!bme.begin(0x76)) {
		Serial.println("Could not find a valid BME280 sensor, check wiring!");
		while (1);
	}
}

void loop() {
	Serial.print("Temperature = ");
	Serial.print(bme.readTemperature());
	Serial.println("*C");

	Serial.print("Pressure = ");
	Serial.print(bme.readPressure() / 100.0F);
	Serial.println("hPa");

	Serial.print("Approx. Altitude = ");
	Serial.print(bme.readAltitude(SEALEVELPRESSURE_HPA));
	Serial.println("m");

	Serial.print("Humidity = ");
	Serial.print(bme.readHumidity());
	Serial.println("%");

	Serial.println();
	delay(1000);
}

You should see a similar output in the serial monitor.

Code Explanation:

The sketch begins by including three libraries, namely Wire.h, Adafruit Sensor.h, and Adafruit BME280.h.

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

The variable SEALEVELPRESSURE_HPA is then defined. This variable stores the sea level pressure in millibars and is used to calculate absolute altitude for a given pressure by comparing it to the sea level pressure. The default value (1013.25) is used in this sketch, but for accurate results, replace it with the current sea level pressure at your location.

An object of the Adafruit BME280 library is also created so that we can access its functions.

#define SEALEVELPRESSURE_HPA (1013.25)

Adafruit_BME280 bme;

In the setup section of the code, we initialize the serial communication with the PC and call the begin() function.

The begin(I2C_ADDR) function takes the module’s I2C address as a parameter. If you changed the I2C address of your module, you must specify it correctly. This function initializes the I2C interface with the given I2C address and validates the chip ID. It then soft-resets the chip and waits for the sensor to calibrate after wake-up.

Serial.begin(9600);

if (!bme.begin(0x76)) {
	Serial.println("Could not find a valid BME280 sensor, check wiring!");
	while (1);
}

In the loop section of the code, we use the following functions to read temperature, relative humidity, and barometric pressure from the BME280 module.

readTemperature() function returns the temperature.

readPressure() function returns the barometric pressure.

readAltitude(SEALEVELPRESSURE_HPA) function computes the altitude (in meters) by comparing the specified atmospheric pressure (in hPa) to the sea-level pressure (in hPa).

readHumidity() function returns the relative humidity.

Serial.print("Temperature = ");
Serial.print(bme.readTemperature());
Serial.println("*C");

Serial.print("Pressure = ");
Serial.print(bme.readPressure() / 100.0F);
Serial.println("hPa");

Serial.print("Approx. Altitude = ");
Serial.print(bme.readAltitude(SEALEVELPRESSURE_HPA));
Serial.println("m");

Serial.print("Humidity = ");
Serial.print(bme.readHumidity());
Serial.println("%");