README

This is a driver for the Bosch BME280 temperature/pressure/humidity sensor, for use with MicroPython on ESP8266 boards. It is also compatible with the BMP280 which provides the same interface but temperature + pressure only.

About the BME280

The Bosch BME280 Environmental Sensor is a combined temperature, pressure and humidity sensor. It can communicate via I2C or SPI; this driver uses I2C.

See the datasheet at https://www.adafruit.com/datasheets/BST-BME280_DS001-10.pdf for details.

Using the library

Copy bme280.py onto the board (e.g. using webrepl_cli.py). Then:

import machine
import bme280

i2c = machine.I2C(scl=machine.Pin(5), sda=machine.Pin(4))
bme = bme280.BME280(i2c=i2c)

print(bme.values)

Detailed usage

The values property is a convenience function that provides a tuple of human-readable string values to quickly check that the sensor is working. In practice, the method to use is read_compensated_data() which returns a (temperature, pressure, humidity)-tuple:

• temperature: the temperature in hundredths of a degree celsius. For example, the value 2534 indicates a temperature of 25.34 degrees.
• pressure: the atmospheric pressure. This 32-bit value consists of 24 bits indicating the integer value, and 8 bits indicating the fractional value. To get a value in Pascals, divide the return value by 256. For example, a value of 24674867 indicates 96386.2Pa, or 963.862hPa.
• humidity: the relative humidity. This 32-bit value consists of 22 bits indicating the integer value, and 10 bits indicating the fractional value. To get a value in %RH, divide the return value by 1024. For example, a value of 47445 indicates 46.333%RH.