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https://github.com/robert-hh/BME280

Micropython driver for the BME280 sensor, target platform Pycom devices
https://github.com/robert-hh/BME280

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Micropython driver for the BME280 sensor, target platform Pycom devices

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# BME280 Micropython driver for the BME280 sensor



This is a driver for the Bosch BME280 temperature/pressure/humidity sensor,

for use with MicroPython on Pycom of ESP8266 boards. It is also compatible with

the BMP280 which provides the same interface but temperature + pressure only.



Two different variants of the library are supplied. bme20_int.py uses integer

arithmetic, bme280_float.py uses float arithmetic for the compensation  of the

raw values. The results are (almost) the identical, but the format of the

returned values differs.



## 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.bosch-sensortec.com/media/boschsensortec/downloads/datasheets/bst-bme280-ds002.pdf

for details.



## Class



bme = BME280(mode=BME280_OSAMPLE_8, address=BME280_I2CADDR, i2c=i2c)



`mode` is the setting for oversampling of the humidity value. It must be either a single

int or a tuple of 3 ints, specifying (mode_hum, mode_temp, mode_pressure). `address` is the i2c

address used, and i2c must be a I2C object.



## Properties



### values = BME280.values



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



### altitude = bme.altitude

Altitude in m. The altitude is calculated based on the value given to

the property sealevel (see below). Obviously, this value does not have to be the

sealevel pressure, but any pressure you may select, for instance to measure

altitude difference in general.



### bme.sealevel = sealevel

### sealevel = bme.sealevel

Setting and getting the pressure for altitude calculation.

The default is 101325 Pa, but you can use your local

QNH in Pa, or set a local pressure to determine altitude difference.



### dew_point = bme.dew_point

Returns the dew_point temperature (°C) calculated from the actual temperature and humidity.



## Methods



### values = read_compensated_data(result = None)



Values is an array of either integers (bme280_int.py) of floats (bme280_float.py),

holding the values of temperature, pressure and humidity.

The format differs for integers and floats:



#### Integer formats:

* `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.



#### Float formats

* `temperature`:  the temperature in degree Celsius.

* `pressure`: the atmospheric pressure in Pascal.

* `humidity`: the relative humidity in percent.



If the parameter result is supplied as an array of the appropriate type, The

return values will in addition be stored in that array, and the array will be

returned.



### read_raw_data(result)

Store the raw sensor data into the array result, which must provide space for three

32 bit integers, as provided for instance by `array("i", [0, 0, 0])`. This

method is used internally.



### Example



Copy `bme280_float.py` onto the board. Then:



``` python

#

# this script for the rp2040 port assumes the I2C connections at

# GPIO8 and 9. At the RPi Pico, these are the board pins 11 and 12

# Please check that pull-up resistors are in place at sda and scl.

#

import machine, Pin

import bme280_float as bme280



i2c = machine.I2C(0, sda=machine.Pin(8), scl=machine.Pin(9))

bme = bme280.BME280(i2c=i2c)



print(bme.values)

```