kopia lustrzana https://github.com/robert-hh/BME280
Robert Hammelrath
robert-hh
rodzic
0da810b150
commit
aaf2a4f271
202
README.md
202
README.md
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# BME280 Micropython driver for the BME280 sensor
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This is a driver for the Bosch BME280 temperature/pressure/humidity sensor,
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for use with MicroPython on Pycom of ESP8266 boards. It is also compatible with
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the BMP280 which provides the same interface but temperature + pressure only.
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Two different variants of the library are supplied. bme20_int.py uses integer
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arithmetic, bme280_float.py uses float arithmetic for the compensation of the
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raw values. The results are (almost) the identical, but the format of the
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returned values differs.
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## About the BME280
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The Bosch BME280 Environmental Sensor is a combined temperature, pressure and
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humidity sensor. It can communicate via I2C or SPI; this driver uses I2C.
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See the datasheet at https://ae-bst.resource.bosch.com/media/_tech/media/datasheets/BST-BME280_DS002.pdf
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for details.
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## Class
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bme= BME280(i2c=i2c, mode=BME280_OSAMPLE_8, address=BME280_I2CADDR)
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mode is the setting for oversampling of the humidity value, address the i2c
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address used.
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## Properties
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### values = BME280.values
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The `values` property is a convenience function that provides a tuple of
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human-readable string values to quickly check that the sensor is working.
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In practice, the method to use is `read_compensated_data()` which returns
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a `(temperature, pressure, humidity)`-tuple
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### altitude = bmp.altitude
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Altitude in m. The altitude is calculated based on the value given to
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the property sealevel (see below). Obviously, this value does not have to be the
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sealevel pressure, but any pressure you may select, for instance to measure
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altitude difference in general.
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### bmp.sealevel = sealevel
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### sealevel = bmp.sealevel
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Setting and getting the pressure for altitude calculation.
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The default is 101325 Pa, but you can use your local
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QNH in Pa, or set a local pressure to determine altitude difference.
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### dew_point = bmp.dew_point
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Returns the dew_point temperature (°C) calculated from the actual temperature and humidity.
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## Methods
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### values = read_compensated_data(result = None)
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Values is an array of either integers (bme280_int.py) of floats (bme280_float.py),
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holding the values of temperature, pressure and humidity.
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The format differs for integers and floats:
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#### Integer formats:
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* `temperature`: the temperature in hundredths of a degree Celsius. For example,
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the value 2534 indicates a temperature of 25.34 degrees.
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* `pressure`: the atmospheric pressure. This 32-bit value consists of 24 bits
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indicating the integer value, and 8 bits indicating the fractional value. To get
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a value in Pascals, divide the return value by 256. For example, a value of
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24674867 indicates 96386.2Pa, or 963.862hPa.
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* `humidity`: the relative humidity. This 32-bit value consists of 22 bits
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indicating the integer value, and 10 bits indicating the fractional value.
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To get a value in %RH, divide the return value by 1024. For example, a value of
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47445 indicates 46.333%RH.
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#### Float formats
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* `temperature`: the temperature in degree Celsius.
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* `pressure`: the atmospheric pressure in Pascal.
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* `humidity`: the relative humidity in percent.
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If the parameter result is supplied as an array of the appropriate type, The
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return values will in addition be stored in that array, and the array will be
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returned.
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### read_raw_data(result)
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Store the raw sensor data into the array result, which must provide space for three
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32 bit integers, as provided for instance by `array("i", [0, 0, 0])`. This
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method is used internally.
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### Example
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Copy `bme280_float.py` onto the board. Then:
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``` python
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#
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# this script assumes the default connection of the I2C bus
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# On pycom devuces that is P9 = SDA, P10 = scl
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#
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import machine
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import bme280_float as bme280
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i2c = machine.I2C()
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bme = bme280.BME280(i2c=i2c)
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print(bme.values)
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```
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# BME280 Micropython driver for the BME280 sensor
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This is a driver for the Bosch BME280 temperature/pressure/humidity sensor,
|
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for use with MicroPython on Pycom of ESP8266 boards. It is also compatible with
|
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the BMP180 which provides the same interface but temperature + pressure only.
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Two different variants of the library are supplied. bme20_int.py uses integer
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arithmetic, bme280_float.py uses float arithmetic for the compensation of the
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raw values. The results are (almost) the identical, but the format of the
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returned values differs.
|
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## About the BME280
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The Bosch BME280 Environmental Sensor is a combined temperature, pressure and
|
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humidity sensor. It can communicate via I2C or SPI; this driver uses I2C.
|
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See the datasheet at https://ae-bst.resource.bosch.com/media/_tech/media/datasheets/BST-BME280_DS002.pdf
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for details.
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## Class
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bme = BME280(i2c=i2c, mode=BME280_OSAMPLE_8, address=BME280_I2CADDR)
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mode is the setting for oversampling of the humidity value, address the i2c
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address used.
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## Properties
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### values = BME280.values
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The `values` property is a convenience function that provides a tuple of
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human-readable string values to quickly check that the sensor is working.
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In practice, the method to use is `read_compensated_data()` which returns
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a `(temperature, pressure, humidity)`-tuple
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### altitude = bme.altitude
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Altitude in m. The altitude is calculated based on the value given to
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the property sealevel (see below). Obviously, this value does not have to be the
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sealevel pressure, but any pressure you may select, for instance to measure
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altitude difference in general.
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### bme.sealevel = sealevel
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### sealevel = bme.sealevel
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Setting and getting the pressure for altitude calculation.
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The default is 101325 Pa, but you can use your local
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QNH in Pa, or set a local pressure to determine altitude difference.
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### dew_point = bme.dew_point
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Returns the dew_point temperature (°C) calculated from the actual temperature and humidity.
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## Methods
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### values = read_compensated_data(result = None)
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Values is an array of either integers (bme280_int.py) of floats (bme280_float.py),
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holding the values of temperature, pressure and humidity.
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The format differs for integers and floats:
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#### Integer formats:
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* `temperature`: the temperature in hundredths of a degree Celsius. For example,
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the value 2534 indicates a temperature of 25.34 degrees.
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* `pressure`: the atmospheric pressure. This 32-bit value consists of 24 bits
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indicating the integer value, and 8 bits indicating the fractional value. To get
|
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a value in Pascals, divide the return value by 256. For example, a value of
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24674867 indicates 96386.2Pa, or 963.862hPa.
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* `humidity`: the relative humidity. This 32-bit value consists of 22 bits
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indicating the integer value, and 10 bits indicating the fractional value.
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To get a value in %RH, divide the return value by 1024. For example, a value of
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47445 indicates 46.333%RH.
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#### Float formats
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* `temperature`: the temperature in degree Celsius.
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* `pressure`: the atmospheric pressure in Pascal.
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* `humidity`: the relative humidity in percent.
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If the parameter result is supplied as an array of the appropriate type, The
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return values will in addition be stored in that array, and the array will be
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returned.
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### read_raw_data(result)
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Store the raw sensor data into the array result, which must provide space for three
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32 bit integers, as provided for instance by `array("i", [0, 0, 0])`. This
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method is used internally.
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### Example
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Copy `bme280_float.py` onto the board. Then:
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``` python
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#
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# this script assumes the default connection of the I2C bus
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# On pycom devuces that is P9 = SDA, P10 = scl
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#
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import machine
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import bme280_float as bme280
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i2c = machine.I2C()
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bme = bme280.BME280(i2c=i2c)
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print(bme.values)
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```
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