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)

# optional, check your local METAR for the current value
bme.sea_level_millibars = 1013.10

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 addition to the formatting the sensor values, it also computes pressure altitude. 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.