mpy_bme280_esp8266/bme280.py

# Author: Paul Cunnane 2016
#
# This module borrows heavily from the Adafruit BME280 Python library
# and the Adafruit GPIO/I2C library. Original copyright notices are reproduced
# below.
#
# Those libraries were written for the Raspberry Pi. This modification is
# intended for the MicroPython and esp8266 boards.
#
# 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)
#
# Based on Adafruit_I2C.py created by Kevin Townsend.
#
# 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 time
from bme280_const import *
from i2c_device import Device

class BME280:
    def __init__(self, mode=BME280_OSAMPLE_1, address=BME280_I2CADDR, i2c=None,
                 **kwargs):
        # Check that mode is valid.
        if mode not in [BME280_OSAMPLE_1, BME280_OSAMPLE_2, BME280_OSAMPLE_4,
                        BME280_OSAMPLE_8, BME280_OSAMPLE_16]:
            raise ValueError(
                'Unexpected mode value {0}. Set mode to one of '
                'BME280_ULTRALOWPOWER, BME280_STANDARD, BME280_HIGHRES, or '
                'BME280_ULTRAHIGHRES'.format(mode))
        self._mode = mode
        self.address = address
        if i2c is None:
            raise ValueError('An I2C object is required.')
        self.i2c = i2c
        # Create I2C device.
        self._device = Device(address, i2c)

        # Load calibration values.
        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 << 24) >> 20
        self.dig_H4 = h4 | (self._device.readU8(BME280_REGISTER_DIG_H5) & 0x0F)

        h5 = self._device.readS8(BME280_REGISTER_DIG_H6)
        h5 = (h5 << 24) >> 20
        self.dig_H5 = h5 | (
            self._device.readU8(BME280_REGISTER_DIG_H5) >> 4 & 0x0F)


        self._device.write8(BME280_REGISTER_CONTROL, 0x3F)
        self.t_fine = 0

    def read_raw_data(self):
        """ Reads the raw (uncompensated) data from the sensor.

            Returns:
                tuple with temperature, pressure, humidity
        """

        meas = self._mode
        self.i2c.writeto_mem(self.address, BME280_REGISTER_CONTROL_HUM,
                             bytearray([meas]))
        meas = self._mode << 5 | self._mode << 2 | 1
        self._device.write8(BME280_REGISTER_CONTROL, meas)
        self.i2c.writeto_mem(self.address, BME280_REGISTER_CONTROL,
                             bytearray([meas]))

        sleep_time = 1250 + 2300 * (1 << self._mode)
        sleep_time = sleep_time + 2300 * (1 << self._mode) + 575
        sleep_time = sleep_time + 2300 * (1 << self._mode) + 575
        time.sleep_us(sleep_time)  # Wait the required time

        # burst readout from 0xF7 to 0xFE, recommended by datasheet
        readout = self.i2c.readfrom_mem(self.address, 0xF7, 8)
        # pressure(0xF7): ((msb << 16) | (lsb << 8) | xlsb) >> 4
        raw_press = ((readout[0] << 16) | (readout[1] << 8) | readout[2]) >> 4
        # temperature(0xFA): ((msb << 16) | (lsb << 8) | xlsb) >> 4
        raw_temp = ((readout[3] << 16) | (readout[4] << 8) | readout[5]) >> 4
        # humidity(0xFD): (msb << 8) | lsb
        raw_hum = (readout[6] << 8) | readout[7]

        return (raw_temp, raw_press, raw_hum)

    def read_raw_temp(self):
        """Reads the raw (uncompensated) temperature from the sensor."""
        meas = self._mode
        self._device.write8(BME280_REGISTER_CONTROL_HUM, meas)
        meas = self._mode << 5 | self._mode << 2 | 1
        self._device.write8(BME280_REGISTER_CONTROL, meas)
        sleep_time = 1250 + 2300 * (1 << self._mode)
        sleep_time = sleep_time + 2300 * (1 << self._mode) + 575
        sleep_time = sleep_time + 2300 * (1 << self._mode) + 575
        time.sleep_us(sleep_time)  # Wait the required time
        msb = self._device.readU8(BME280_REGISTER_TEMP_DATA)
        lsb = self._device.readU8(BME280_REGISTER_TEMP_DATA + 1)
        xlsb = self._device.readU8(BME280_REGISTER_TEMP_DATA + 2)
        raw = ((msb << 16) | (lsb << 8) | xlsb) >> 4
        return raw

    def read_raw_pressure(self):
        """Reads the raw (uncompensated) pressure level from the sensor."""
        """Assumes that the temperature has already been read """
        """i.e. that enough delay has been provided"""
        msb = self._device.readU8(BME280_REGISTER_PRESSURE_DATA)
        lsb = self._device.readU8(BME280_REGISTER_PRESSURE_DATA + 1)
        xlsb = self._device.readU8(BME280_REGISTER_PRESSURE_DATA + 2)
        raw = ((msb << 16) | (lsb << 8) | xlsb) >> 4
        return raw

    def read_raw_humidity(self):
        """Assumes that the temperature has already been read """
        """i.e. that enough delay has been provided"""
        msb = self._device.readU8(BME280_REGISTER_HUMIDITY_DATA)
        lsb = self._device.readU8(BME280_REGISTER_HUMIDITY_DATA + 1)
        raw = (msb << 8) | lsb
        return raw

    def read_temperature(self):
        """Get the compensated temperature in 0.01 of a degree celsius."""
        adc = self.read_raw_temp()
        var1 = ((adc >> 3) - (self.dig_T1 << 1)) * (self.dig_T2 >> 11)
        var2 = ((
            (((adc >> 4) - self.dig_T1) * ((adc >> 4) - self.dig_T1)) >> 12) *
            self.dig_T3) >> 14
        self.t_fine = var1 + var2
        return (self.t_fine * 5 + 128) >> 8

    def read_pressure(self):
        """Gets the compensated pressure in Pascals."""
        adc = self.read_raw_pressure()
        var1 = self.t_fine - 128000
        var2 = var1 * var1 * self.dig_P6
        var2 = var2 + ((var1 * self.dig_P5) << 17)
        var2 = var2 + (self.dig_P4 << 35)
        var1 = (((var1 * var1 * self.dig_P3) >> 8) +
                ((var1 * self.dig_P2) >> 12))
        var1 = (((1 << 47) + var1) * self.dig_P1) >> 33
        if var1 == 0:
            return 0
        p = 1048576 - adc
        p = (((p << 31) - var2) * 3125) // var1
        var1 = (self.dig_P9 * (p >> 13) * (p >> 13)) >> 25
        var2 = (self.dig_P8 * p) >> 19
        return ((p + var1 + var2) >> 8) + (self.dig_P7 << 4)

    def read_humidity(self):
        adc = self.read_raw_humidity()
        # print 'Raw humidity = {0:d}'.format (adc)
        h = self.t_fine - 76800
        h = (((((adc << 14) - (self.dig_H4 << 20) - (self.dig_H5 * h)) +
             16384) >> 15) * (((((((h * self.dig_H6) >> 10) * (((h *
                              self.dig_H3) >> 11) + 32768)) >> 10) + 2097152) *
                              self.dig_H2 + 8192) >> 14))
        h = h - (((((h >> 15) * (h >> 15)) >> 7) * self.dig_H1) >> 4)
        h = 0 if h < 0 else h
        h = 419430400 if h > 419430400 else h
        return h >> 12

    @property
    def values(self):
        """ human readable values """

        t = self.read_temperature()
        ti = t // 100
        td = t - ti * 100

        p = self.read_pressure() // 256
        pi = p // 100
        pd = p - pi * 100

        h = self.read_humidity()
        hi = h // 1024
        hd = h * 100 // 1024 - hi * 100
        return ("{}.{:02d}C".format(ti, td), "{}.{:02d}hPa".format(pi, pd),
                "{}.{:02d}%".format(hi, hd))