import machine
import utime
from machine import Pin, I2C
import ssd1306
from bme280 import *

# Pin configuration for I2C
sda = Pin(0)
scl = Pin(1)

# Initialize I2C
i2c = I2C(0, sda=sda, scl=scl, freq=400000)

# Initialize the BME280 sensor
bme280 = BME280(i2c=i2c)

# Initialize the SSD1306 OLED display
display = ssd1306.SSD1306_I2C(128, 64, i2c)

# Function to update the display with sensor data
def update_display():
    display.fill(0)  # Clear the display

    # Fetch sensor data
    temperature, pressure, humidity = bme.read_compensated_data()

    # Convert pressure to hPa and temperature to Celsius
    pressure_hpa = pressure // 25600
    temperature_c = temperature // 100

    # Display sensor data on the OLED screen
    display.text("Temperature: {:.1f} C".format(temperature_c / 100), 0, 0)
    display.text("Pressure: {:.1f} hPa".format(pressure_hpa / 100), 0, 16)
    display.text("Humidity: {:.1f} %".format(humidity / 1024), 0, 32)

    display.show()  # Update the display

while True:
    update_display()
    utime.sleep(2)  # Update sensor data and display every 2 seconds


main.py

diagram.json

# MicroPython SSD1306 OLED driver, I2C and SPI interfaces
#
# library taken from repository at:
# https://github.com/micropython/micropython/blob/master/drivers/display/ssd1306.py
#
from micropython import const
import framebuf
import time

# Register definitions
SET_CONTRAST = const(0x81)
SET_ENTIRE_ON = const(0xA4)
SET_NORM_INV = const(0xA6)
SET_DISP = const(0xAE)
SET_MEM_ADDR = const(0x20)
SET_COL_ADDR = const(0x21)
SET_PAGE_ADDR = const(0x22)
SET_DISP_START_LINE = const(0x40)
SET_SEG_REMAP = const(0xA0)
SET_MUX_RATIO = const(0xA8)
SET_COM_OUT_DIR = const(0xC0)
SET_DISP_OFFSET = const(0xD3)
SET_COM_PIN_CFG = const(0xDA)
SET_DISP_CLK_DIV = const(0xD5)
SET_PRECHARGE = const(0xD9)
SET_VCOM_DESEL = const(0xDB)
SET_CHARGE_PUMP = const(0x8D)

# Subclassing FrameBuffer provides support for graphics primitives
# http://docs.micropython.org/en/latest/pyboard/library/framebuf.html
class SSD1306(framebuf.FrameBuffer):
    def __init__(self, width, height, external_vcc):
        self.width = width
        self.height = height
        self.external_vcc = external_vcc
        self.pages = self.height // 8
        self.buffer = bytearray(self.pages * self.width)
        super().__init__(self.buffer, self.width, self.height, framebuf.MONO_VLSB)
        self.init_display()

    def init_display(self):
        for cmd in (
            SET_DISP | 0x00,  # off
            # Address setting
            SET_MEM_ADDR,
            0x00,  # horizontal
            # Resolution and layout
            SET_DISP_START_LINE | 0x00,
            SET_SEG_REMAP | 0x01,  # Column addr 127 mapped to SEG0
            SET_MUX_RATIO,
            self.height - 1,
            SET_COM_OUT_DIR | 0x08,  # Scan from COM[N] to COM0
            SET_DISP_OFFSET,
            0x00,
            SET_COM_PIN_CFG,
            0x02 if self.width > 2 * self.height else 0x12,
            # Timing and driving scheme
            SET_DISP_CLK_DIV,
            0x80,
            SET_PRECHARGE,
            0x22 if self.external_vcc else 0xF1,
            SET_VCOM_DESEL,
            0x30,  # 0.83*Vcc
            # Display
            SET_CONTRAST,
            0xFF,  # maximum
            SET_ENTIRE_ON,  # Output follows RAM contents
            SET_NORM_INV,  # Not inverted
            # Charge pump
            SET_CHARGE_PUMP,
            0x10 if self.external_vcc else 0x14,
            SET_DISP | 0x01,
        ):  # On
            self.write_cmd(cmd)
        self.fill(0)
        self.show()

    def poweroff(self):
        self.write_cmd(SET_DISP | 0x00)

    def poweron(self):
        self.write_cmd(SET_DISP | 0x01)

    def contrast(self, contrast):
        self.write_cmd(SET_CONTRAST)
        self.write_cmd(contrast)

    def invert(self, invert):
        self.write_cmd(SET_NORM_INV | (invert & 1))

    def show(self):
        x0 = 0
        x1 = self.width - 1
        if self.width == 64:
            # Displays with width of 64 pixels are shifted by 32
            x0 += 32
            x1 += 32
        self.write_cmd(SET_COL_ADDR)
        self.write_cmd(x0)
        self.write_cmd(x1)
        self.write_cmd(SET_PAGE_ADDR)
        self.write_cmd(0)
        self.write_cmd(self.pages - 1)
        self.write_data(self.buffer)


class SSD1306_I2C(SSD1306):
    def __init__(self, width, height, i2c, addr=0x3C, external_vcc=False):
        self.i2c = i2c
        self.addr = addr
        self.temp = bytearray(2)
        self.write_list = [b"\x40", None]  # Co=0, D/C#=1
        super().__init__(width, height, external_vcc)

    def write_cmd(self, cmd):
        self.temp[0] = 0x80  # Co=1, D/C#=0
        self.temp[1] = cmd
        self.i2c.writeto(self.addr, self.temp)

    def write_data(self, buf):
        self.write_list[1] = buf
        self.i2c.writevto(self.addr, self.write_list)

# Only required for SPI version (not covered in this project)
class SSD1306_SPI(SSD1306):
    def __init__(self, width, height, spi, dc, res, cs, external_vcc=False):
        self.rate = 10 * 1024 * 1024
        dc.init(dc.OUT, value=0)
        res.init(res.OUT, value=0)
        cs.init(cs.OUT, value=1)
        self.spi = spi
        self.dc = dc
        self.res = res
        self.cs = cs

        self.res(1)
        time.sleep_ms(1)
        self.res(0)
        time.sleep_ms(10)
        self.res(1)
        super().__init__(width, height, external_vcc)

    def write_cmd(self, cmd):
        self.spi.init(baudrate=self.rate, polarity=0, phase=0)
        self.cs(1)
        self.dc(0)
        self.cs(0)
        self.spi.write(bytearray([cmd]))
        self.cs(1)

    def write_data(self, buf):
        self.spi.init(baudrate=self.rate, polarity=0, phase=0)
        self.cs(1)
        self.dc(1)
        self.cs(0)
        self.spi.write(buf)
        self.cs(1)


ssd1306.py

# Updated 2018 and 2020
# This module is based on the below cited resources, which are all
# based on the documentation as provided in the Bosch Data Sheet and
# the sample implementation provided therein.
#
# Final Document: BST-BME280-DS002-15
#
# Authors: Paul Cunnane 2016, Peter Dahlebrg 2016
#
# This module borrows from the Adafruit BME280 Python 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 ustruct import unpack, unpack_from
from array import array

# BME280 default address.
BME280_I2CADDR = 0x76

# Operating Modes
BME280_OSAMPLE_1 = 1
BME280_OSAMPLE_2 = 2
BME280_OSAMPLE_4 = 3
BME280_OSAMPLE_8 = 4
BME280_OSAMPLE_16 = 5

BME280_REGISTER_CONTROL_HUM = 0xF2
BME280_REGISTER_STATUS = 0xF3
BME280_REGISTER_CONTROL = 0xF4

MODE_SLEEP = const(0)
MODE_FORCED = const(1)
MODE_NORMAL = const(3)

BME280_TIMEOUT = const(100)  # about 1 second timeout

class BME280:

    def __init__(self,
                 mode=BME280_OSAMPLE_8,
                 address=BME280_I2CADDR,
                 i2c=None,
                 **kwargs):
        # Check that mode is valid.
        if type(mode) is tuple and len(mode) == 3:
            self._mode_hum, self._mode_temp, self._mode_press = mode
        elif type(mode) == int:
            self._mode_hum, self._mode_temp, self._mode_press = mode, mode, mode
        else:
            raise ValueError("Wrong type for the mode parameter, must be int or a 3 element tuple")

        for mode in (self._mode_hum, self._mode_temp, self._mode_press):
            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.address = address
        if i2c is None:
            raise ValueError('An I2C object is required.')
        self.i2c = i2c
        self.__sealevel = 101325

        # load calibration data
        dig_88_a1 = self.i2c.readfrom_mem(self.address, 0x88, 26)
        dig_e1_e7 = self.i2c.readfrom_mem(self.address, 0xE1, 7)

        self.dig_T1, self.dig_T2, self.dig_T3, self.dig_P1, \
            self.dig_P2, self.dig_P3, self.dig_P4, self.dig_P5, \
            self.dig_P6, self.dig_P7, self.dig_P8, self.dig_P9, \
            _, self.dig_H1 = unpack("<HhhHhhhhhhhhBB", dig_88_a1)

        self.dig_H2, self.dig_H3, self.dig_H4,\
            self.dig_H5, self.dig_H6 = unpack("<hBbhb", dig_e1_e7)
        # unfold H4, H5, keeping care of a potential sign
        self.dig_H4 = (self.dig_H4 * 16) + (self.dig_H5 & 0xF)
        self.dig_H5 //= 16

        # temporary data holders which stay allocated
        self._l1_barray = bytearray(1)
        self._l8_barray = bytearray(8)
        self._l3_resultarray = array("i", [0, 0, 0])

        self._l1_barray[0] = self._mode_temp << 5 | self._mode_press << 2 | MODE_SLEEP
        self.i2c.writeto_mem(self.address, BME280_REGISTER_CONTROL,
                             self._l1_barray)
        self.t_fine = 0

    def read_raw_data(self, result):
        """ Reads the raw (uncompensated) data from the sensor.

            Args:
                result: array of length 3 or alike where the result will be
                stored, in temperature, pressure, humidity order
            Returns:
                None
        """

        self._l1_barray[0] = self._mode_hum
        self.i2c.writeto_mem(self.address, BME280_REGISTER_CONTROL_HUM,
                             self._l1_barray)
        self._l1_barray[0] = self._mode_temp << 5 | self._mode_press << 2 | MODE_FORCED
        self.i2c.writeto_mem(self.address, BME280_REGISTER_CONTROL,
                             self._l1_barray)

        # Wait for conversion to complete
        for _ in range(BME280_TIMEOUT):
            if self.i2c.readfrom_mem(self.address, BME280_REGISTER_STATUS, 1)[0] & 0x08:
                time.sleep_ms(10)  # still busy
            else:
                break  # Sensor ready
        else:
            raise RuntimeError("Sensor BME280 not ready")

        # burst readout from 0xF7 to 0xFE, recommended by datasheet
        self.i2c.readfrom_mem_into(self.address, 0xF7, self._l8_barray)
        readout = self._l8_barray
        # 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]

        result[0] = raw_temp
        result[1] = raw_press
        result[2] = raw_hum

    def read_compensated_data(self, result=None):
        """ Reads the data from the sensor and returns the compensated data.

            Args:
                result: array of length 3 or alike where the result will be
                stored, in temperature, pressure, humidity order. You may use
                this to read out the sensor without allocating heap memory

            Returns:
                array with temperature, pressure, humidity. Will be the one
                from the result parameter if not None
        """
        self.read_raw_data(self._l3_resultarray)
        raw_temp, raw_press, raw_hum = self._l3_resultarray
        # temperature
        var1 = (raw_temp/16384.0 - self.dig_T1/1024.0) * self.dig_T2
        var2 = raw_temp/131072.0 - self.dig_T1/8192.0
        var2 = var2 * var2 * self.dig_T3
        self.t_fine = int(var1 + var2)
        temp = (var1 + var2) / 5120.0
        temp = max(-40, min(85, temp))

        # pressure
        var1 = (self.t_fine/2.0) - 64000.0
        var2 = var1 * var1 * self.dig_P6 / 32768.0 + var1 * self.dig_P5 * 2.0
        var2 = (var2 / 4.0) + (self.dig_P4 * 65536.0)
        var1 = (self.dig_P3 * var1 * var1 / 524288.0 + self.dig_P2 * var1) / 524288.0
        var1 = (1.0 + var1 / 32768.0) * self.dig_P1
        if (var1 == 0.0):
            pressure = 30000  # avoid exception caused by division by zero
        else:
            p = ((1048576.0 - raw_press) - (var2 / 4096.0)) * 6250.0 / var1
            var1 = self.dig_P9 * p * p / 2147483648.0
            var2 = p * self.dig_P8 / 32768.0
            pressure = p + (var1 + var2 + self.dig_P7) / 16.0
            pressure = max(30000, min(110000, pressure))

        # humidity
        h = (self.t_fine - 76800.0)
        h = ((raw_hum - (self.dig_H4 * 64.0 + self.dig_H5 / 16384.0 * h)) *
             (self.dig_H2 / 65536.0 * (1.0 + self.dig_H6 / 67108864.0 * h *
                                       (1.0 + self.dig_H3 / 67108864.0 * h))))
        humidity = h * (1.0 - self.dig_H1 * h / 524288.0)
        # humidity = max(0, min(100, humidity))

        if result:
            result[0] = temp
            result[1] = pressure
            result[2] = humidity
            return result

        return array("f", (temp, pressure, humidity))

    @property
    def sealevel(self):
        return self.__sealevel

    @sealevel.setter
    def sealevel(self, value):
        if 30000 < value < 120000:  # just ensure some reasonable value
            self.__sealevel = value

    @property
    def altitude(self):
        '''
        Altitude in m.
        '''
        from math import pow
        try:
            p = 44330 * (1.0 - pow(self.read_compensated_data()[1] /
                                   self.__sealevel, 0.1903))
        except:
            p = 0.0
        return p

    @property
    def dew_point(self):
        """
        Compute the dew point temperature for the current Temperature
        and Humidity measured pair
        """
        from math import log
        t, p, h = self.read_compensated_data()
        h = (log(h, 10) - 2) / 0.4343 + (17.62 * t) / (243.12 + t)
        return 243.12 * h / (17.62 - h)

    @property
    def values(self):
        """ human readable values """

        t, p, h = self.read_compensated_data()

        return ("{:.2f}C".format(t), "{:.2f}hPa".format(p/100),
                "{:.2f}%".format(h))


bme280_float.py

# Updated 2018 and 2020
# This module is based on the below cited resources, which are all
# based on the documentation as provided in the Bosch Data Sheet and
# the sample implementation provided therein.
#
# Final Document: BST-BME280-DS002-15
#
# Authors: Paul Cunnane 2016, Peter Dahlebrg 2016
#
# This module borrows from the Adafruit BME280 Python 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 ustruct import unpack, unpack_from
from array import array

# BME280 default address.
BME280_I2CADDR = 0x76

# Operating Modes
BME280_OSAMPLE_1 = 1
BME280_OSAMPLE_2 = 2
BME280_OSAMPLE_4 = 3
BME280_OSAMPLE_8 = 4
BME280_OSAMPLE_16 = 5

BME280_REGISTER_CONTROL_HUM = 0xF2
BME280_REGISTER_STATUS = 0xF3
BME280_REGISTER_CONTROL = 0xF4

MODE_SLEEP = const(0)
MODE_FORCED = const(1)
MODE_NORMAL = const(3)

BME280_TIMEOUT = const(100)  # about 1 second timeout


class BME280:

    def __init__(self,
                 mode=BME280_OSAMPLE_8,
                 address=BME280_I2CADDR,
                 i2c=None,
                 **kwargs):
        # Check that mode is valid.
        if type(mode) is tuple and len(mode) == 3:
            self._mode_hum, self._mode_temp, self._mode_press = mode
        elif type(mode) == int:
            self._mode_hum, self._mode_temp, self._mode_press = mode, mode, mode
        else:
            raise ValueError("Wrong type for the mode parameter, must be int or a 3 element tuple")

        for mode in (self._mode_hum, self._mode_temp, self._mode_press):
            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.address = address
        if i2c is None:
            raise ValueError('An I2C object is required.')
        self.i2c = i2c
        self.__sealevel = 101325

        # load calibration data
        dig_88_a1 = self.i2c.readfrom_mem(self.address, 0x88, 26)
        dig_e1_e7 = self.i2c.readfrom_mem(self.address, 0xE1, 7)
        self.dig_T1, self.dig_T2, self.dig_T3, self.dig_P1, \
            self.dig_P2, self.dig_P3, self.dig_P4, self.dig_P5, \
            self.dig_P6, self.dig_P7, self.dig_P8, self.dig_P9, \
            _, self.dig_H1 = unpack("<HhhHhhhhhhhhBB", dig_88_a1)

        self.dig_H2, self.dig_H3, self.dig_H4,\
            self.dig_H5, self.dig_H6 = unpack("<hBbhb", dig_e1_e7)
        # unfold H4, H5, keeping care of a potential sign
        self.dig_H4 = (self.dig_H4 * 16) + (self.dig_H5 & 0xF)
        self.dig_H5 //= 16

        self.t_fine = 0

        # temporary data holders which stay allocated
        self._l1_barray = bytearray(1)
        self._l8_barray = bytearray(8)
        self._l3_resultarray = array("i", [0, 0, 0])

        self._l1_barray[0] = self._mode_temp << 5 | self._mode_press << 2 | MODE_SLEEP
        self.i2c.writeto_mem(self.address, BME280_REGISTER_CONTROL,
                             bytearray([0x3c | MODE_SLEEP]))

    def read_raw_data(self, result):
        """ Reads the raw (uncompensated) data from the sensor.

            Args:
                result: array of length 3 or alike where the result will be
                stored, in temperature, pressure, humidity order
            Returns:
                None
        """

        self._l1_barray[0] = self._mode_hum
        self.i2c.writeto_mem(self.address, BME280_REGISTER_CONTROL_HUM,
                             self._l1_barray)
        self._l1_barray[0] = self._mode_temp << 5 | self._mode_press << 2 | MODE_FORCED
        self.i2c.writeto_mem(self.address, BME280_REGISTER_CONTROL,
                             self._l1_barray)

        # Wait for conversion to complete
        for _ in range(BME280_TIMEOUT):
            if self.i2c.readfrom_mem(self.address, BME280_REGISTER_STATUS, 1)[0] & 0x08:
                time.sleep_ms(10)  # still busy
            else:
                break  # Sensor ready
        else:
            raise RuntimeError("Sensor BME280 not ready")

        # burst readout from 0xF7 to 0xFE, recommended by datasheet
        self.i2c.readfrom_mem_into(self.address, 0xF7, self._l8_barray)
        readout = self._l8_barray
        # 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]

        result[0] = raw_temp
        result[1] = raw_press
        result[2] = raw_hum

    def read_compensated_data(self, result=None):
        """ Reads the data from the sensor and returns the compensated data.

            Args:
                result: array of length 3 or alike where the result will be
                stored, in temperature, pressure, humidity order. You may use
                this to read out the sensor without allocating heap memory

            Returns:
                array with temperature, pressure, humidity. Will be the one
                from the result parameter if not None
        """
        self.read_raw_data(self._l3_resultarray)
        raw_temp, raw_press, raw_hum = self._l3_resultarray
        # temperature
        var1 = (((raw_temp // 8) - (self.dig_T1 * 2)) * self.dig_T2) // 2048
        var2 = (raw_temp // 16) - self.dig_T1
        var2 = (((var2 * var2) // 4096) * self.dig_T3) // 16384
        self.t_fine = var1 + var2
        temp = (self.t_fine * 5 + 128) // 256

        # 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:
            pressure = 0
        else:
            p = ((((1048576 - raw_press) << 31) - var2) * 3125) // var1
            var1 = (self.dig_P9 * (p >> 13) * (p >> 13)) >> 25
            var2 = (self.dig_P8 * p) >> 19
            pressure = ((p + var1 + var2) >> 8) + (self.dig_P7 << 4)

        # humidity
        h = self.t_fine - 76800
        h = (((((raw_hum << 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
        humidity = h >> 12

        if result:
            result[0] = temp
            result[1] = pressure
            result[2] = humidity
            return result

        return array("i", (temp, pressure, humidity))

    @property
    def sealevel(self):
        return self.__sealevel

    @sealevel.setter
    def sealevel(self, value):
        if 300 < value < 1200:  # just ensure some reasonable value
            self.__sealevel = value

    @property
    def altitude(self):
        '''
        Altitude in m.
        '''
        from math import pow
        try:
            p = 44330 * (1.0 - pow((self.read_compensated_data()[1] / 256) /
                                   self.__sealevel, 0.1903))
        except:
            p = 0.0
        return p

    @property
    def dew_point(self):
        """
        Compute the dew point temperature for the current Temperature
        and Humidity measured pair
        """
        from math import log
        t, p, h = self.read_compensated_data()
        t /= 100
        h /= 1024
        h = (log(h, 10) - 2) / 0.4343 + (17.62 * t) / (243.12 + t)
        return (243.12 * h / (17.62 - h)) * 100

    @property
    def values(self):
        """ human readable values """

        t, p, h = self.read_compensated_data()

        p = p / 256

        h = h / 1024
        return ("{}C".format(t / 100), "{:.02f}hPa".format(p/100),
                "{:.02f}%".format(h))
