Adafruit_BME280.py

# Copyright (c) 2014 Adafruit Industries
# Author: Tony DiCola
#
# Based on the BMP280 driver with BME280 changes provided by
# David J Taylor, Edinburgh (www.satsignal.eu). Additional functions added
# by Tom Nardi (www.digifail.com)
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
import logging
import time


# BME280 default address.
BME280_I2CADDR = 0x77

# Operating Modes
BME280_OSAMPLE_1 = 1
BME280_OSAMPLE_2 = 2
BME280_OSAMPLE_4 = 3
BME280_OSAMPLE_8 = 4
BME280_OSAMPLE_16 = 5

# Standby Settings
BME280_STANDBY_0p5 = 0
BME280_STANDBY_62p5 = 1
BME280_STANDBY_125 = 2
BME280_STANDBY_250 = 3
BME280_STANDBY_500 = 4
BME280_STANDBY_1000 = 5
BME280_STANDBY_10 = 6
BME280_STANDBY_20 = 7

# Filter Settings
BME280_FILTER_off = 0
BME280_FILTER_2 = 1
BME280_FILTER_4 = 2
BME280_FILTER_8 = 3
BME280_FILTER_16 = 4

# BME280 Registers

BME280_REGISTER_DIG_T1 = 0x88  # Trimming parameter registers
BME280_REGISTER_DIG_T2 = 0x8A
BME280_REGISTER_DIG_T3 = 0x8C

BME280_REGISTER_DIG_P1 = 0x8E
BME280_REGISTER_DIG_P2 = 0x90
BME280_REGISTER_DIG_P3 = 0x92
BME280_REGISTER_DIG_P4 = 0x94
BME280_REGISTER_DIG_P5 = 0x96
BME280_REGISTER_DIG_P6 = 0x98
BME280_REGISTER_DIG_P7 = 0x9A
BME280_REGISTER_DIG_P8 = 0x9C
BME280_REGISTER_DIG_P9 = 0x9E

BME280_REGISTER_DIG_H1 = 0xA1
BME280_REGISTER_DIG_H2 = 0xE1
BME280_REGISTER_DIG_H3 = 0xE3
BME280_REGISTER_DIG_H4 = 0xE4
BME280_REGISTER_DIG_H5 = 0xE5
BME280_REGISTER_DIG_H6 = 0xE6
BME280_REGISTER_DIG_H7 = 0xE7

BME280_REGISTER_CHIPID = 0xD0
BME280_REGISTER_VERSION = 0xD1
BME280_REGISTER_SOFTRESET = 0xE0

BME280_REGISTER_STATUS = 0xF3
BME280_REGISTER_CONTROL_HUM = 0xF2
BME280_REGISTER_CONTROL = 0xF4
BME280_REGISTER_CONFIG = 0xF5
BME280_REGISTER_DATA = 0xF7


class BME280(object):
    def __init__(self, t_mode=BME280_OSAMPLE_1, p_mode=BME280_OSAMPLE_1, h_mode=BME280_OSAMPLE_1,
                 standby=BME280_STANDBY_250, filter=BME280_FILTER_off, address=BME280_I2CADDR, i2c=None,
                 **kwargs):
        self._logger = logging.getLogger('Adafruit_BMP.BMP085')
        # Check that t_mode is valid.
        if t_mode not in [BME280_OSAMPLE_1, BME280_OSAMPLE_2, BME280_OSAMPLE_4,
                        BME280_OSAMPLE_8, BME280_OSAMPLE_16]:
            raise ValueError(
                'Unexpected t_mode value {0}.'.format(t_mode))
        self._t_mode = t_mode
        # Check that p_mode is valid.
        if p_mode not in [BME280_OSAMPLE_1, BME280_OSAMPLE_2, BME280_OSAMPLE_4,
                        BME280_OSAMPLE_8, BME280_OSAMPLE_16]:
            raise ValueError(
                'Unexpected p_mode value {0}.'.format(p_mode))
        self._p_mode = p_mode
        # Check that h_mode is valid.
        if h_mode not in [BME280_OSAMPLE_1, BME280_OSAMPLE_2, BME280_OSAMPLE_4,
                        BME280_OSAMPLE_8, BME280_OSAMPLE_16]:
            raise ValueError(
                'Unexpected h_mode value {0}.'.format(h_mode))
        self._h_mode = h_mode
        # Check that standby is valid.
        if standby not in [BME280_STANDBY_0p5, BME280_STANDBY_62p5, BME280_STANDBY_125, BME280_STANDBY_250,
                        BME280_STANDBY_500, BME280_STANDBY_1000, BME280_STANDBY_10, BME280_STANDBY_20]:
            raise ValueError(
                'Unexpected standby value {0}.'.format(standby))
        self._standby = standby
        # Check that filter is valid.
        if filter not in [BME280_FILTER_off, BME280_FILTER_2, BME280_FILTER_4, BME280_FILTER_8, BME280_FILTER_16]:
            raise ValueError(
                'Unexpected filter value {0}.'.format(filter))
        self._filter = filter
        # Create I2C device.
        if i2c is None:
            import Adafruit_GPIO.I2C as I2C
            i2c = I2C
        # Create device, catch permission errors
        try:
            self._device = i2c.get_i2c_device(address, **kwargs)
        except IOError:
            print("Unable to communicate with sensor, check permissions.")
            exit()
        # Load calibration values.
        self._load_calibration()
        self._device.write8(BME280_REGISTER_CONTROL, 0x24)  # Sleep mode
        time.sleep(0.002)
        self._device.write8(BME280_REGISTER_CONFIG, ((standby << 5) | (filter << 2)))
        time.sleep(0.002)
        self._device.write8(BME280_REGISTER_CONTROL_HUM, h_mode)  # Set Humidity Oversample
        self._device.write8(BME280_REGISTER_CONTROL, ((t_mode << 5) | (p_mode << 2) | 3))  # Set Temp/Pressure Oversample and enter Normal mode
        self.t_fine = 0.0

    def _load_calibration(self):

        self.dig_T1 = self._device.readU16LE(BME280_REGISTER_DIG_T1)
        self.dig_T2 = self._device.readS16LE(BME280_REGISTER_DIG_T2)
        self.dig_T3 = self._device.readS16LE(BME280_REGISTER_DIG_T3)

        self.dig_P1 = self._device.readU16LE(BME280_REGISTER_DIG_P1)
        self.dig_P2 = self._device.readS16LE(BME280_REGISTER_DIG_P2)
        self.dig_P3 = self._device.readS16LE(BME280_REGISTER_DIG_P3)
        self.dig_P4 = self._device.readS16LE(BME280_REGISTER_DIG_P4)
        self.dig_P5 = self._device.readS16LE(BME280_REGISTER_DIG_P5)
        self.dig_P6 = self._device.readS16LE(BME280_REGISTER_DIG_P6)
        self.dig_P7 = self._device.readS16LE(BME280_REGISTER_DIG_P7)
        self.dig_P8 = self._device.readS16LE(BME280_REGISTER_DIG_P8)
        self.dig_P9 = self._device.readS16LE(BME280_REGISTER_DIG_P9)

        self.dig_H1 = self._device.readU8(BME280_REGISTER_DIG_H1)
        self.dig_H2 = self._device.readS16LE(BME280_REGISTER_DIG_H2)
        self.dig_H3 = self._device.readU8(BME280_REGISTER_DIG_H3)
        self.dig_H6 = self._device.readS8(BME280_REGISTER_DIG_H7)

        h4 = self._device.readS8(BME280_REGISTER_DIG_H4)
        h4 = (h4 << 4)
        self.dig_H4 = h4 | (self._device.readU8(BME280_REGISTER_DIG_H5) & 0x0F)

        h5 = self._device.readS8(BME280_REGISTER_DIG_H6)
        h5 = (h5 << 4)
        self.dig_H5 = h5 | (
        self._device.readU8(BME280_REGISTER_DIG_H5) >> 4 & 0x0F)

        '''
        print '0xE4 = {0:2x}'.format (self._device.readU8 (BME280_REGISTER_DIG_H4))
        print '0xE5 = {0:2x}'.format (self._device.readU8 (BME280_REGISTER_DIG_H5))
        print '0xE6 = {0:2x}'.format (self._device.readU8 (BME280_REGISTER_DIG_H6))

        print 'dig_H1 = {0:d}'.format (self.dig_H1)
        print 'dig_H2 = {0:d}'.format (self.dig_H2)
        print 'dig_H3 = {0:d}'.format (self.dig_H3)
        print 'dig_H4 = {0:d}'.format (self.dig_H4)
        print 'dig_H5 = {0:d}'.format (self.dig_H5)
        print 'dig_H6 = {0:d}'.format (self.dig_H6)
        '''

    def read_raw_temp(self):
        """Waits for reading to become available on device."""
        """Does a single burst read of all data values from device."""
        """Returns the raw (uncompensated) temperature from the sensor."""
        while (self._device.readU8(BME280_REGISTER_STATUS) & 0x08):    # Wait for conversion to complete (TODO : add timeout)
            time.sleep(0.002)
        self.BME280Data = self._device.readList(BME280_REGISTER_DATA, 8)
        raw = ((self.BME280Data[3] << 16) | (self.BME280Data[4] << 8) | self.BME280Data[5]) >> 4
        return raw

    def read_raw_pressure(self):
        """Returns the raw (uncompensated) pressure level from the sensor."""
        """Assumes that the temperature has already been read """
        """i.e. that BME280Data[] has been populated."""
        raw = ((self.BME280Data[0] << 16) | (self.BME280Data[1] << 8) | self.BME280Data[2]) >> 4
        return raw

    def read_raw_humidity(self):
        """Returns the raw (uncompensated) humidity value from the sensor."""
        """Assumes that the temperature has already been read """
        """i.e. that BME280Data[] has been populated."""
        raw = (self.BME280Data[6] << 8) | self.BME280Data[7]
        return raw

    def read_temperature(self):
        """Gets the compensated temperature in degrees celsius."""
        # float in Python is double precision
        UT = float(self.read_raw_temp())
        var1 = (UT / 16384.0 - float(self.dig_T1) / 1024.0) * float(self.dig_T2)
        var2 = ((UT / 131072.0 - float(self.dig_T1) / 8192.0) * (
        UT / 131072.0 - float(self.dig_T1) / 8192.0)) * float(self.dig_T3)
        self.t_fine = int(var1 + var2)
        temp = (var1 + var2) / 5120.0
        return temp

    def read_pressure(self):
        """Gets the compensated pressure in Pascals."""
        adc = float(self.read_raw_pressure())
        var1 = float(self.t_fine) / 2.0 - 64000.0
        var2 = var1 * var1 * float(self.dig_P6) / 32768.0
        var2 = var2 + var1 * float(self.dig_P5) * 2.0
        var2 = var2 / 4.0 + float(self.dig_P4) * 65536.0
        var1 = (
               float(self.dig_P3) * var1 * var1 / 524288.0 + float(self.dig_P2) * var1) / 524288.0
        var1 = (1.0 + var1 / 32768.0) * float(self.dig_P1)
        if var1 == 0:
            return 0
        p = 1048576.0 - adc
        p = ((p - var2 / 4096.0) * 6250.0) / var1
        var1 = float(self.dig_P9) * p * p / 2147483648.0
        var2 = p * float(self.dig_P8) / 32768.0
        p = p + (var1 + var2 + float(self.dig_P7)) / 16.0
        return p

    def read_humidity(self):
        adc = float(self.read_raw_humidity())
        # print 'Raw humidity = {0:d}'.format (adc)
        h = float(self.t_fine) - 76800.0
        h = (adc - (float(self.dig_H4) * 64.0 + float(self.dig_H5) / 16384.0 * h)) * (
        float(self.dig_H2) / 65536.0 * (1.0 + float(self.dig_H6) / 67108864.0 * h * (
        1.0 + float(self.dig_H3) / 67108864.0 * h)))
        h = h * (1.0 - float(self.dig_H1) * h / 524288.0)
        if h > 100:
            h = 100
        elif h < 0:
            h = 0
        return h

    def read_temperature_f(self):
        # Wrapper to get temp in F
        celsius = self.read_temperature()
        temp = celsius * 1.8 + 32
        return temp

    def read_pressure_inches(self):
        # Wrapper to get pressure in inches of Hg
        pascals = self.read_pressure()
        inches = pascals * 0.0002953
        return inches

    def read_dewpoint(self):
        # Return calculated dewpoint in C, only accurate at > 50% RH
        celsius = self.read_temperature()
        humidity = self.read_humidity()
        dewpoint = celsius - ((100 - humidity) / 5)
        return dewpoint

    def read_dewpoint_f(self):
        # Return calculated dewpoint in F, only accurate at > 50% RH
        dewpoint_c = self.read_dewpoint()
        dewpoint_f = dewpoint_c * 1.8 + 32
        return dewpoint_f