It's easy to use the BMP280 sensor with CircuitPython and the Adafruit CircuitPython BMP280 module. This module allows you to easily write Python code that reads the temperature and pressure from the sensor.
You can use this sensor with any CircuitPython microcontroller board or with a computer that has GPIO and Python thanks to Adafruit_Blinka, our CircuitPython-for-Python compatibility library.
First wire up a BMP280 to your board exactly as shown on the previous pages for Arduino. You can use either I2C or SPI wiring, although it's recommended to use I2C for simplicity. Here's an example of wiring a Feather to the sensor with I2C:
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Board 3V to sensor VIN (red wire on STEMMA version)
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Board GND to sensor GND (black wire on STEMMA version)
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Board SCL to sensor SCK (yellow wire on STEMMA version)
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Board SDA to sensor SDI (blue wire on STEMMA version)
And an example of a Feather M0 wired with hardware SPI:
- Board 3V to sensor VIN
- Board GND to sensor GND
- Board SCK to sensor SCK
- Board MOSI to sensor SDI
- Board MISO to sensor SDO
- Board D5 to sensor CS (or use any other free digital I/O pin)
Since there's dozens of Linux computers/boards you can use we will show wiring for Raspberry Pi. For other platforms, please visit the guide for CircuitPython on Linux to see whether your platform is supported.
Here's the Raspberry Pi wired with I2C:
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Pi 3V3 to sensor VIN (red wire on STEMMA version)
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Pi GND to sensor GND (black wire on STEMMA version)
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Pi SCL to sensor SCK (yellow wire on STEMMA version)
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Pi SDA to sensor SDI (blue wire on STEMMA version)
And an example on the Raspberry Pi 3 Model B wired with SPI:
- Pi 3V3 to sensor VIN
- Pi GND to sensor GND
- Pi MOSI to sensor SDI
- Pi MISO to sensor SDO
- Pi SCLK to sensor SCK
- Pi #5 to sensor CS (or use any other free GPIO pin)
You'll need to install the Adafruit CircuitPython BMP280 library on your CircuitPython board.
First make sure you are running the latest version of Adafruit CircuitPython for your board.
Next you'll need to install the necessary libraries to use the hardware--carefully follow the steps to find and install these libraries from Adafruit's CircuitPython library bundle. Our CircuitPython starter guide has a great page on how to install the library bundle.
For non-express boards like the Trinket M0 or Gemma M0, you'll need to manually install the necessary libraries from the bundle:
- adafruit_bmp280.mpy
- adafruit_bus_device
Before continuing make sure your board's lib folder or root filesystem has the adafruit_bmp280.mpy, and adafruit_bus_device files and folders copied over.
Next connect to the board's serial REPL so you are at the CircuitPython >>> prompt.
You'll need to install the Adafruit_Blinka library that provides the CircuitPython support in Python. This may also require enabling I2C on your platform and verifying you are running Python 3. Since each platform is a little different, and Linux changes often, please visit the CircuitPython on Linux guide to get your computer ready!
Once that's done, from your command line run the following command:
sudo pip3 install adafruit-circuitpython-bmp280
If your default Python is version 3 you may need to run 'pip' instead. Just make sure you aren't trying to use CircuitPython on Python 2.x, it isn't supported!
CircuitPython & Python Usage
To demonstrate the usage of the sensor we'll initialize it and read the temperature, humidity, and more from the board's Python REPL.
If you're using an I2C connection run the following code to import the necessary modules and initialize the I2C connection with the sensor:
import board import adafruit_bmp280 i2c = board.I2C() sensor = adafruit_bmp280.Adafruit_BMP280_I2C(i2c)
Or if you're using a SPI connection run this code instead to setup the SPI connection and sensor:
import board import digitalio import adafruit_bmp280 spi = board.SPI() cs = digitalio.DigitalInOut(board.D5) sensor = adafruit_bmp280.Adafruit_BMP280_SPI(spi, cs)
Now you're ready to read values from the sensor using any of these properties:
- temperature - The sensor temperature in degrees Celsius.
- pressure - The pressure in hPa.
- altitude - The altitude in meters.
For example to print temperature and pressure:
print('Temperature: {} degrees C'.format(sensor.temperature))
print('Pressure: {}hPa'.format(sensor.pressure))
For altitude you'll want to set the pressure at sea level for your location to get the most accurate measure (remember these sensors can only infer altitude based on pressure and need a set calibration point). Look at your local weather report for a pressure at sea level reading and set the seaLevelhPA property:
sensor.sea_level_pressure = 1013.25
Then read the altitude property for a more accurate altitude reading (but remember this altitude will fluctuate based on atmospheric pressure changes!):
print('Altitude: {} meters'.format(sensor.altitude))
That's all there is to using the BMP280 sensor with CircuitPython!
Here's a starting example that will print out the temperature, pressure and altitude every 2 seconds:
# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries
# SPDX-License-Identifier: MIT
"""Simpletest Example that shows how to get temperature,
pressure, and altitude readings from a BMP280"""
import time
import board
# import digitalio # For use with SPI
import adafruit_bmp280
# Create sensor object, communicating over the board's default I2C bus
i2c = board.I2C() # uses board.SCL and board.SDA
# i2c = board.STEMMA_I2C() # For using the built-in STEMMA QT connector on a microcontroller
bmp280 = adafruit_bmp280.Adafruit_BMP280_I2C(i2c)
# OR Create sensor object, communicating over the board's default SPI bus
# spi = board.SPI()
# bmp_cs = digitalio.DigitalInOut(board.D10)
# bmp280 = adafruit_bmp280.Adafruit_BMP280_SPI(spi, bmp_cs)
# change this to match the location's pressure (hPa) at sea level
bmp280.sea_level_pressure = 1013.25
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)
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