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Lesson 20: Temperature, Humidity & Pressure Sensor (BMP280)

In this lesson, you will learn how to connect and read data from a BMP280 sensor that measures temperature, humidity, and pressure using a Raspberry Pi. You’ll set up the sensor and write a Python script to measure environmental data including temperature, atmospheric pressure, and altitude.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
Universal Maker Sensor Kit	94	Universal Maker Sensor Kit

You can also buy them separately from the links below.

Component Introduction	Purchase Link
Raspberry Pi 5	BUY
Temperature, Humidity & Pressure Sensor (BMP280)	BUY
Breadboard	BUY

Wiring

Install Library

Note

The adafruit-circuitpython-bmp280 library relies on Blinka, so please ensure that Blinka has been installed. To install libraries, refer to Insatll Adafruit_Blinka (CircuitPython) - Optional.

Before installing the library, please make sure that the virtual Python environment is activated:

source ~/env/bin/activate

Install adafruit-circuitpython-bmp280 library:

pip install adafruit-circuitpython-bmp280

Run the Code

Note

Please ensure that you have installed the Python library required for running the code according to the “Install Library” steps.
Before running the code, please make sure that you have activated the virtual Python environment with blinka installed. You can activate the virtual environment using a command like this:
```
source ~/env/bin/activate
```
Find the code for this lesson in universal-maker-sensor-kit-main/pi/ directory, or directly copy and paste the code below. Execute the code by running the following commands in terminal:
```
python 22_touch_sensor_module.py
```

import time
import board

import adafruit_bmp280

# Create sensor object, communicating over the board's default I2C bus
i2c = board.I2C()  # uses board.SCL and board.SDA
bmp280 = adafruit_bmp280.Adafruit_BMP280_I2C(i2c,address=0x76)

# change this to match the location's pressure (hPa) at sea level
bmp280.sea_level_pressure = 1013.25

try:
   while True:
      print("\nTemperature: %0.1f C" % bmp280.temperature)
      print("Pressure: %0.1f hPa" % bmp280.pressure)
      print("Altitude = %0.2f meters" % bmp280.altitude)
      time.sleep(2)
except KeyboardInterrupt:
    print("Exit")  # Exit on CTRL+C

Code Analysis

Setting up the sensor

Import necessary libraries and create an object to interact with the BMP280 sensor. board.I2C() sets up the I2C communication. adafruit_bmp280.Adafruit_BMP280_I2C(i2c, address=0x76) initializes the BMP280 sensor with its I2C address.

For more detail about the adafruit_bmp280 library, please refer to adafruit/Adafruit_CircuitPython_BMP280.
```
import time
import board
import adafruit_bmp280
i2c = board.I2C()
bmp280 = adafruit_bmp280.Adafruit_BMP280_I2C(i2c, address=0x76)
```
Configuring sea-level pressure

Set the sea_level_pressure property of the BMP280 object. This value is needed to calculate altitude.
```
bmp280.sea_level_pressure = 1013.25
```

Reading data in a loop

Use a while True loop to continuously read data from the sensor. bmp280.temperature, bmp280.pressure, and bmp280.altitude read the temperature, pressure, and altitude, respectively. time.sleep(2) pauses the loop for 2 seconds.

try:
   while True:
      print("\nTemperature: %0.1f C" % bmp280.temperature)
      print("Pressure: %0.1f hPa" % bmp280.pressure)
      print("Altitude = %0.2f meters" % bmp280.altitude)
      time.sleep(2)
except KeyboardInterrupt:
   print("Exit")

Handling interruptions

The try and except KeyboardInterrupt: block allows the program to exit gracefully when you press CTRL+C.
```
try:
   # while loop code here
except KeyboardInterrupt:
   print("Exit")
```