# 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("> 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))