Python & CircuitPython Test

It's easy to use the BME280 sensor with Python or CircuitPython and the Adafruit CircuitPython BME280 module.  This module allows you to easily write Python code that reads the humidity, temperature, pressure, and more 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.

CircuitPython Microcontroller Wiring

First wire up a BME280 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 M0 to the sensor with I2C:

  • Board 3V to sensor VIN
  • Board GND to sensor GND
  • Board SCL to sensor SCK
  • Board SDA to sensor SDI

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)

Python Computer Wiring

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:

  • Pi 3V3 to sensor VIN
  • Pi GND to sensor GND
  • Pi SCL to sensor SCK
  • Pi SDA to sensor SDI

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)

CircuitPython Installation of BME280 Library

You'll need to install the Adafruit CircuitPython BME280 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_bme280.mpy
  • adafruit_bus_device

Before continuing make sure your board's lib folder or root filesystem has the adafruit_bme280.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.

Python Installation of BME280 Library

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-bme280

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 busio
import adafruit_bme280
i2c = busio.I2C(board.SCL, board.SDA)
bme280 = adafruit_bme280.Adafruit_BME280_I2C(i2c)

Or if you're using a SPI connection run this code instead to setup the SPI connection and sensor:

import board
import busio
import digitalio
import adafruit_bme280
spi = busio.SPI(board.SCK, MOSI=board.MOSI, MISO=board.MISO)
cs = digitalio.DigitalInOut(board.D5)
bme280 = adafruit_bme280.Adafruit_BME280_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.
  • humidity - The percent humidity as a value from 0 to 100%.
  • pressure - The pressure in hPa.
  • altitude - The altitude in meters.

For example to print temperature, humidity, and pressure:

print("\nTemperature: %0.1f C" % bme280.temperature)
print("Humidity: %0.1f %%" % bme280.humidity)
print("Pressure: %0.1f hPa" % bme280.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 sea_level_pressure property:

bme280.sea_level_pressure = 1013.4

Then read the altitude property for a more accurate altitude reading (but remember this altitude will fluctuate based on atmospheric pressure changes!):

print("Altitude = %0.2f meters" % bme280.altitude)

You can use the BME280 temperature and humidity to calculate the dew point using the Magnus formula! For this example, you'll need to import an additional library: math. Run the following code:

import math
b = 17.62
c = 243.12
gamma = (b * bme280.temperature /(c + bme280.temperature)) + math.log(bme280.humidity / 100.0)
dewpoint = (c * gamma) / (b - gamma)
print(dewpoint)

That's all there is to using the BME280 sensor with CircuitPython!

Full Example Code

import time

import board
import busio
import adafruit_bme280

# Create library object using our Bus I2C port
i2c = busio.I2C(board.SCL, board.SDA)
bme280 = adafruit_bme280.Adafruit_BME280_I2C(i2c)

# OR create library object using our Bus SPI port
#spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
#bme_cs = digitalio.DigitalInOut(board.D10)
#bme280 = adafruit_bme280.Adafruit_BME280_SPI(spi, bme_cs)

# change this to match the location's pressure (hPa) at sea level
bme280.sea_level_pressure = 1013.25

while True:
    print("\nTemperature: %0.1f C" % bme280.temperature)
    print("Humidity: %0.1f %%" % bme280.humidity)
    print("Pressure: %0.1f hPa" % bme280.pressure)
    print("Altitude = %0.2f meters" % bme280.altitude)
    time.sleep(2)
This guide was first published on Jul 24, 2015. It was last updated on Sep 20, 2018. This page (Python & CircuitPython Test) was last updated on Aug 14, 2018.