commit d8d78924a8f20928d5d33d9c47eaeca8c97f31d7 Author: hh Date: Sun Nov 11 16:01:02 2018 +0100 bme280_xxx.py: Microypthon driver for the BME280 sensor Initial commit. Files: bme280_int.py: Driver using integer arithmetic for compensation bme280_float.py: Driver using floating point arithmetic for compensation README.md: Documentation bmetest.py: Sample test code. diff --git a/README.md b/README.md new file mode 100644 index 0000000..6b6d30c --- /dev/null +++ b/README.md @@ -0,0 +1,85 @@ +# BME280 Micropython driver for the BME280 sensor + +This is a driver for the Bosch BME280 temperature/pressure/humidity sensor, +for use with MicroPython on Pycom of ESP8266 boards. It is also compatible with +the BMP280 which provides the same interface but temperature + pressure only. + +Two different variants of the library are supplied. bme20_int.py uses integer +arithmetic. bme280_float.py uses float arithmetic for the compensation of the +raw values. The results are (almost) the identical, but the format of the +returned values differs. + +## About the BME280 + +The Bosch BME280 Environmental Sensor is a combined temperature, pressure and +humidity sensor. It can communicate via I2C or SPI; this driver uses I2C. + +See the datasheet at https://ae-bst.resource.bosch.com/media/_tech/media/datasheets/BST-BME280_DS002.pdf +for details. + +## Class + +bme= BME280(i2c=i2c, mode=BME280_OSAMPLE_8, address=BME280_I2CADDR) + +mode is the setting for oversampling of the humidity value, address the i2c +address used. + +## Property + +### values = BME280.value + +The `values` property is a convenience function that provides a tuple of +human-readable string values to quickly check that the sensor is working. +In practice, the method to use is `read_compensated_data()` which returns +a `(temperature, pressure, humidity)`-tuple + +## Methods + +### values = read_compensated_data(result = None) + +Values is an array of either integers of floats, holding the values of temperature, +pressure and humidity. The format differs for integers and floats: + +#### Integer formats: +* `temperature`: the temperature in hundredths of a degree Celsius. For example, +the value 2534 indicates a temperature of 25.34 degrees. +* `pressure`: the atmospheric pressure. This 32-bit value consists of 24 bits +indicating the integer value, and 8 bits indicating the fractional value. To get +a value in Pascals, divide the return value by 256. For example, a value of +24674867 indicates 96386.2Pa, or 963.862hPa. +* `humidity`: the relative humidity. This 32-bit value consists of 22 bits +indicating the integer value, and 10 bits indicating the fractional value. +To get a value in %RH, divide the return value by 1024. For example, a value of +47445 indicates 46.333%RH. + +#### Float formats +* `temperature`: the temperature in degree Celsius. +* `pressure`: the atmospheric pressure in Pascal. +* `humidity`: the relative humidity in percent. + +If the parameter result is supplied as an array of the appropriate type, The +return values will in addition be stored in that array, and the array will be +returned. + +### read_raw_data(result) +Store the raw sensor data into the array result, which must provide space for three +32 bit integers, as provided for instance by `array("i", [0, 0, 0])`. This +method is used internally. + +### Example + +Copy `bme280.py` onto the board. Then: + +``` python +# +# this script assumes the default connection of the I2C bus +# On pycom devuces that is P9 = SDA, P10 = scl +# +import machine +import bme280 + +i2c = machine.I2C() +bme = bme280.BME280(i2c=i2c) + +print(bme.values) +``` diff --git a/bme280_float.py b/bme280_float.py new file mode 100644 index 0000000..3d97e97 --- /dev/null +++ b/bme280_float.py @@ -0,0 +1,197 @@ +# 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_CONTROL = 0xF4 + + +class BME280: + + def __init__(self, + mode=BME280_OSAMPLE_8, + 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 + + # 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) & 0x0F) + + self.dig_H6 = unpack_from("> 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 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)) + diff --git a/bme280_int.py b/bme280_int.py new file mode 100644 index 0000000..d5f2fcc --- /dev/null +++ b/bme280_int.py @@ -0,0 +1,203 @@ +# 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_CONTROL = 0xF4 + + +class BME280: + + def __init__(self, + mode=BME280_OSAMPLE_8, + 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 + + # 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) + + self.dig_H6 = unpack_from("> 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 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)) + diff --git a/bmetest.py b/bmetest.py new file mode 100644 index 0000000..1756555 --- /dev/null +++ b/bmetest.py @@ -0,0 +1,9 @@ +# +# Example. Using I2C at P9, P10 +# +from machine import I2C +from bme280 import * +i2c=I2C() +bme280 = BME280(i2c=i2c) +bme280.values +