# SPDX-FileCopyrightText: 2017 ladyada for Adafruit Industries
#
# SPDX-License-Identifier: MIT
"""
`adafruit_bme280.basic`
=========================================================================================
CircuitPython driver from BME280 Temperature, Humidity and Barometric
Pressure sensor
* Author(s): ladyada, Jose David M.
Implementation Notes
--------------------
**Hardware:**
* `Adafruit BME280 Temperature, Humidity and Barometric Pressure sensor
<https://www.adafruit.com/product/2652>`_ (Product ID: 2652)
**Software and Dependencies:**
* Adafruit CircuitPython firmware for the supported boards:
https://circuitpython.org/downloads
* Adafruit's Bus Device library:
https://github.com/adafruit/Adafruit_CircuitPython_BusDevice
"""
import math
import struct
from time import sleep
from micropython import const
from adafruit_bme280.protocol import I2C_Impl, SPI_Impl
try:
import typing # pylint: disable=unused-import
from busio import I2C, SPI
from digitalio import DigitalInOut
except ImportError:
pass
__version__ = "2.6.4"
__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_BME280.git"
# I2C ADDRESS/BITS/SETTINGS
# -----------------------------------------------------------------------
"""General Information"""
_BME280_ADDRESS = const(0x77)
_BME280_CHIPID = const(0x60)
_BME280_REGISTER_CHIPID = const(0xD0)
"""overscan values for temperature, pressure, and humidity"""
OVERSCAN_X1 = const(0x01)
OVERSCAN_X16 = const(0x05)
"""mode values"""
_BME280_MODES = (0x00, 0x01, 0x03)
"""iir_filter values"""
IIR_FILTER_DISABLE = const(0)
"""
standby timeconstant values
TC_X[_Y] where X=milliseconds and Y=tenths of a millisecond
"""
STANDBY_TC_125 = const(0x02) # 125ms
"""mode values"""
MODE_SLEEP = const(0x00)
MODE_FORCE = const(0x01)
MODE_NORMAL = const(0x03)
"""Other Registers"""
_BME280_REGISTER_SOFTRESET = const(0xE0)
_BME280_REGISTER_CTRL_HUM = const(0xF2)
_BME280_REGISTER_STATUS = const(0xF3)
_BME280_REGISTER_CTRL_MEAS = const(0xF4)
_BME280_REGISTER_CONFIG = const(0xF5)
_BME280_REGISTER_TEMPDATA = const(0xFA)
_BME280_REGISTER_HUMIDDATA = const(0xFD)
[docs]
class Adafruit_BME280:
"""Driver from BME280 Temperature, Humidity and Barometric Pressure sensor
.. note::
The operational range of the BME280 is 300-1100 hPa.
Pressure measurements outside this range may not be as accurate.
"""
# pylint: disable=too-many-instance-attributes
def __init__(self, bus_implementation: typing.Union[I2C_Impl, SPI_Impl]) -> None:
"""Check the BME280 was found, read the coefficients and enable the sensor"""
# Check device ID.
self._bus_implementation = bus_implementation
chip_id = self._read_byte(_BME280_REGISTER_CHIPID)
if _BME280_CHIPID != chip_id:
raise RuntimeError("Failed to find BME280! Chip ID 0x%x" % chip_id)
# Set some reasonable defaults.
self._iir_filter = IIR_FILTER_DISABLE
self.overscan_humidity = OVERSCAN_X1
self.overscan_temperature = OVERSCAN_X1
self.overscan_pressure = OVERSCAN_X16
self._t_standby = STANDBY_TC_125
self._mode = MODE_SLEEP
self._reset()
self._read_coefficients()
self._write_ctrl_meas()
self._write_config()
self.sea_level_pressure = 1013.25
"""Pressure in hectoPascals at sea level. Used to calibrate `altitude`."""
self._t_fine = None
def _read_temperature(self) -> None:
# perform one measurement
if self.mode != MODE_NORMAL:
self.mode = MODE_FORCE
# Wait for conversion to complete
while self._get_status() & 0x08:
sleep(0.002)
raw_temperature = (
self._read24(_BME280_REGISTER_TEMPDATA) / 16
) # lowest 4 bits get dropped
var1 = (
raw_temperature / 16384.0 - self._temp_calib[0] / 1024.0
) * self._temp_calib[1]
var2 = (
(raw_temperature / 131072.0 - self._temp_calib[0] / 8192.0)
* (raw_temperature / 131072.0 - self._temp_calib[0] / 8192.0)
) * self._temp_calib[2]
self._t_fine = int(var1 + var2)
def _reset(self) -> None:
"""Soft reset the sensor"""
self._write_register_byte(_BME280_REGISTER_SOFTRESET, 0xB6)
sleep(0.004) # Datasheet says 2ms. Using 4ms just to be safe
def _write_ctrl_meas(self) -> None:
"""
Write the values to the ctrl_meas and ctrl_hum registers in the device
ctrl_meas sets the pressure and temperature data acquisition options
ctrl_hum sets the humidity oversampling and must be written to first
"""
self._write_register_byte(_BME280_REGISTER_CTRL_HUM, self.overscan_humidity)
self._write_register_byte(_BME280_REGISTER_CTRL_MEAS, self._ctrl_meas)
def _get_status(self) -> int:
"""Get the value from the status register in the device"""
return self._read_byte(_BME280_REGISTER_STATUS)
def _read_config(self) -> int:
"""Read the value from the config register in the device"""
return self._read_byte(_BME280_REGISTER_CONFIG)
def _write_config(self) -> None:
"""Write the value to the config register in the device"""
normal_flag = False
if self._mode == MODE_NORMAL:
# Writes to the config register may be ignored while in Normal mode
normal_flag = True
self.mode = MODE_SLEEP # So we switch to Sleep mode first
self._write_register_byte(_BME280_REGISTER_CONFIG, self._config)
if normal_flag:
self.mode = MODE_NORMAL
@property
def mode(self) -> int:
"""
Operation mode
Allowed values are the constants MODE_*
"""
return self._mode
@mode.setter
def mode(self, value: int) -> None:
if not value in _BME280_MODES:
raise ValueError("Mode '%s' not supported" % (value))
self._mode = value
self._write_ctrl_meas()
@property
def _config(self) -> int:
"""Value to be written to the device's config register"""
config = 0
if self.mode == 0x03: # MODE_NORMAL
config += self._t_standby << 5
if self._iir_filter:
config += self._iir_filter << 2
return config
@property
def _ctrl_meas(self) -> int:
"""Value to be written to the device's ctrl_meas register"""
ctrl_meas = self.overscan_temperature << 5
ctrl_meas += self.overscan_pressure << 2
ctrl_meas += self.mode
return ctrl_meas
@property
def temperature(self) -> float:
"""The compensated temperature in degrees Celsius."""
self._read_temperature()
return self._t_fine / 5120.0
@property
def pressure(self) -> float:
"""
The compensated pressure in hectoPascals.
"""
self._read_temperature()
# Algorithm from the BME280 driver
# https://github.com/BoschSensortec/BME280_driver/blob/master/bme280.c
adc = (
self._read24(0xF7) / 16 # BME280_REGISTER_PRESSUREDATA
) # lowest 4 bits get dropped
var1 = float(self._t_fine) / 2.0 - 64000.0
var2 = var1 * var1 * self._pressure_calib[5] / 32768.0
var2 = var2 + var1 * self._pressure_calib[4] * 2.0
var2 = var2 / 4.0 + self._pressure_calib[3] * 65536.0
var3 = self._pressure_calib[2] * var1 * var1 / 524288.0
var1 = (var3 + self._pressure_calib[1] * var1) / 524288.0
var1 = (1.0 + var1 / 32768.0) * self._pressure_calib[0]
if not var1: # avoid exception caused by division by zero
raise ArithmeticError(
"Invalid result possibly related to error while reading the calibration registers"
)
pressure = 1048576.0 - adc
pressure = ((pressure - var2 / 4096.0) * 6250.0) / var1
var1 = self._pressure_calib[8] * pressure * pressure / 2147483648.0
var2 = pressure * self._pressure_calib[7] / 32768.0
pressure = pressure + (var1 + var2 + self._pressure_calib[6]) / 16.0
pressure /= 100
return pressure
@property
def relative_humidity(self) -> float:
"""
The relative humidity in RH %
"""
return self.humidity
@property
def humidity(self) -> float:
"""
The relative humidity in RH %
"""
self._read_temperature()
hum = self._read_register(0xFD, 2) # BME280_REGISTER_HUMIDDATA
adc = float(hum[0] << 8 | hum[1])
# Algorithm from the BME280 driver
# https://github.com/BoschSensortec/BME280_driver/blob/master/bme280.c
var1 = float(self._t_fine) - 76800.0
var2 = (
self._humidity_calib[3] * 64.0 + (self._humidity_calib[4] / 16384.0) * var1
)
var3 = adc - var2
var4 = self._humidity_calib[1] / 65536.0
var5 = 1.0 + (self._humidity_calib[2] / 67108864.0) * var1
var6 = 1.0 + (self._humidity_calib[5] / 67108864.0) * var1 * var5
var6 = var3 * var4 * (var5 * var6)
humidity = var6 * (1.0 - self._humidity_calib[0] * var6 / 524288.0)
if humidity > 100:
return 100
if humidity < 0:
return 0
# else...
return humidity
@property
def altitude(self) -> float:
"""The altitude based on current :attr:`pressure` versus the sea level pressure
(``sea_level_pressure``) - which you must enter ahead of time)"""
pressure = self.pressure # in Si units for hPascal
return 44330 * (1.0 - math.pow(pressure / self.sea_level_pressure, 0.1903))
def _read_coefficients(self) -> None:
"""Read & save the calibration coefficients"""
coeff = self._read_register(0x88, 24) # BME280_REGISTER_DIG_T1
coeff = list(struct.unpack("<HhhHhhhhhhhh", bytes(coeff)))
coeff = [float(i) for i in coeff]
self._temp_calib = coeff[:3]
self._pressure_calib = coeff[3:]
self._humidity_calib = [0] * 6
self._humidity_calib[0] = self._read_byte(0xA1) # BME280_REGISTER_DIG_H1
coeff = self._read_register(0xE1, 7) # BME280_REGISTER_DIG_H2
coeff = list(struct.unpack("<hBbBbb", bytes(coeff)))
self._humidity_calib[1] = float(coeff[0])
self._humidity_calib[2] = float(coeff[1])
self._humidity_calib[3] = float((coeff[2] << 4) | (coeff[3] & 0xF))
self._humidity_calib[4] = float((coeff[4] << 4) | (coeff[3] >> 4))
self._humidity_calib[5] = float(coeff[5])
def _read_byte(self, register: int) -> int:
"""Read a byte register value and return it"""
return self._read_register(register, 1)[0]
def _read24(self, register: int) -> float:
"""Read an unsigned 24-bit value as a floating point and return it."""
ret = 0.0
for b in self._read_register(register, 3):
ret *= 256.0
ret += float(b & 0xFF)
return ret
def _read_register(self, register: int, length: int) -> bytearray:
return self._bus_implementation.read_register(register, length)
def _write_register_byte(self, register: int, value: int) -> None:
self._bus_implementation.write_register_byte(register, value)
[docs]
class Adafruit_BME280_I2C(Adafruit_BME280):
"""Driver for BME280 connected over I2C
:param ~busio.I2C i2c: The I2C bus the BME280 is connected to.
:param int address: I2C device address. Defaults to :const:`0x77`.
but another address can be passed in as an argument
.. note::
The operational range of the BMP280 is 300-1100 hPa.
Pressure measurements outside this range may not be as accurate.
**Quickstart: Importing and using the BME280**
Here is an example of using the :class:`Adafruit_BME280_I2C`.
First you will need to import the libraries to use the sensor
.. code-block:: python
import board
from adafruit_bme280 import basic as adafruit_bme280
Once this is done you can define your `board.I2C` object and define your sensor object
.. code-block:: python
i2c = board.I2C() # uses board.SCL and board.SDA
bme280 = adafruit_bme280.Adafruit_BME280_I2C(i2c)
You need to setup the pressure at sea level
.. code-block:: python
bme280.sea_level_pressure = 1013.25
Now you have access to the :attr:`temperature`, :attr:`relative_humidity`
:attr:`pressure` and :attr:`altitude` attributes
.. code-block:: python
temperature = bme280.temperature
relative_humidity = bme280.relative_humidity
pressure = bme280.pressure
altitude = bme280.altitude
"""
def __init__(self, i2c: I2C, address: int = 0x77) -> None: # BME280_ADDRESS
super().__init__(I2C_Impl(i2c, address))
[docs]
class Adafruit_BME280_SPI(Adafruit_BME280):
"""Driver for BME280 connected over SPI
:param ~busio.SPI spi: SPI device
:param ~digitalio.DigitalInOut cs: Chip Select
:param int baudrate: Clock rate, default is 100000. Can be changed with :meth:`baudrate`
.. note::
The operational range of the BMP280 is 300-1100 hPa.
Pressure measurements outside this range may not be as accurate.
**Quickstart: Importing and using the BME280**
Here is an example of using the :class:`Adafruit_BME280_SPI` class.
First you will need to import the libraries to use the sensor
.. code-block:: python
import board
from digitalio import DigitalInOut
from adafruit_bme280 import basic as adafruit_bme280
Once this is done you can define your `board.SPI` object and define your sensor object
.. code-block:: python
cs = digitalio.DigitalInOut(board.D10)
spi = board.SPI()
bme280 = adafruit_bme280.Adafruit_BME280_SPI(spi, cs)
You need to setup the pressure at sea level
.. code-block:: python
bme280.sea_level_pressure = 1013.25
Now you have access to the :attr:`temperature`, :attr:`relative_humidity`
:attr:`pressure` and :attr:`altitude` attributes
.. code-block:: python
temperature = bme280.temperature
relative_humidity = bme280.relative_humidity
pressure = bme280.pressure
altitude = bme280.altitude
"""
def __init__(self, spi: SPI, cs: DigitalInOut, baudrate: int = 100000) -> None:
super().__init__(SPI_Impl(spi, cs, baudrate))