''' bmp085 is a micropython module for the Bosch bmp085 sensor. It measures temperature as well as pressure, with a high enough resolution to calculate altitude. data-sheet: BST-BMP085-DS000-05.pdf The MIT License (MIT) Copyright (c) 2014 Sebastian Plamauer, oeplse@gmail.com Update 2018: - streamlined the code, especially __init__() - added a setter/getter for the sealevel pressure - return hPa for pressure. - remove all memory allocations from nextgauge() - simplified the calculation, using integer arithmetic and shifts where possible, making use if the unlimited integer size in Python. Since these number can get very large, heap memory may get allocted - remove try/except at places where it cannot fail - use ticks_diff() instead of arithmetic difference 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. ''' from ustruct import unpack as unp import math import time # BMP085 class class BMP085(): ''' Module for the BMP085 pressure sensor. ''' # init def __init__(self, i2c=None): # internal module defines if i2c is None: raise ValueError("The I2C bus must be specified") else: self._bmp_i2c = i2c self._bmp_addr = 119 # fix self.chip_id = self._bmp_i2c.readfrom_mem(self._bmp_addr, 0xD0, 2) self._delays = (7, 8, 14, 28) self._diff_sign = time.ticks_diff(1, 0) # read calibration data from EEPROM (self._AC1, self._AC2, self._AC3, self._AC4, self._AC5, self._AC6, self._B1, self._B2, self._MB, self._MC, self._MD) = \ unp('>hhhHHHhhhhh', self._bmp_i2c.readfrom_mem(self._bmp_addr, 0xAA, 22)) # settings to be adjusted by user self._oversample = 3 self._baseline = 1013.25 # output preset self._UT_raw = bytearray(2) self._B5 = 0 self._MLX = bytearray(3) self._COMMAND = bytearray(1) self.gauge = self.makegauge() # Generator instance for _ in range(128): next(self.gauge) time.sleep_ms(1) def compvaldump(self): ''' Returns a list of all compensation values ''' return [self._AC1, self._AC2, self._AC3, self._AC4, self._AC5, self._AC6, self._B1, self._B2, self._MB, self._MC, self._MD, self._oversample] # gauge raw def makegauge(self): ''' Generator refreshing the raw measurments. ''' while True: self._COMMAND[0] = 0x2e self._bmp_i2c.writeto_mem(self._bmp_addr, 0xF4, self._COMMAND) t_start = time.ticks_ms() while (time.ticks_diff(time.ticks_ms(), t_start) * self._diff_sign) <= 5: # 5mS delay yield None try: self._bmp_i2c.readfrom_mem_into(self._bmp_addr, 0xf6, self._UT_raw) except: yield None self._COMMAND[0] = 0x34 | (self._oversample << 6) self._bmp_i2c.writeto_mem(self._bmp_addr, 0xF4, self._COMMAND) t_pressure_ready = self._delays[self._oversample] t_start = time.ticks_ms() while (time.ticks_diff(time.ticks_ms(), t_start) * self._diff_sign) <= t_pressure_ready: yield None try: self._bmp_i2c.readfrom_mem_into(self._bmp_addr, 0xf6, self._MLX) except: yield None yield True def blocking_read(self): if next(self.gauge) is not None: # Discard old data pass while next(self.gauge) is None: pass @property def sealevel(self): return self._baseline @sealevel.setter def sealevel(self, value): if 300 < value < 1200: # just ensure some reasonable value self._baseline = value @property def oversample(self): return self._oversample @oversample.setter def oversample(self, value): if value in range(4): self._oversample = value else: print('oversample can only be 0, 1, 2 or 3, using 3 instead') self._oversample = 3 @property def temperature(self): ''' Temperature in degree C. ''' next(self.gauge) X1 = ((unp(">H", self._UT_raw)[0] - self._AC6) * self._AC5) >> 15 X2 = (self._MC << 11) // (X1 + self._MD) self._B5 = X1 + X2 return ((self._B5 + 8) >> 4) / 10.0 @property def pressure(self): ''' Pressure in hPa. ''' self.temperature # Get values for temperature AND pressure UP = (((self._MLX[0] << 16) + (self._MLX[1] << 8) + self._MLX[2]) >> (8 - self._oversample)) B6 = self._B5 - 4000 X1 = (self._B2 * ((B6 * B6) >> 12)) >> 11 X2 = (self._AC2 * B6) >> 11 B3 = (((self._AC1 * 4 + X1 + X2) << self._oversample) + 2) >> 2 X1 = (self._AC3 * B6) >> 13 X2 = (self._B1 * ((B6 * B6) >> 12)) >> 16 X3 = ((X1 + X2) + 2) >> 2 B4 = (self._AC4 * (X3 + 32768)) >> 15 B7 = (UP - B3) * (50000 >> self._oversample) p = (B7 * 2) // B4 X1 = (((p >> 8) * (p >> 8)) * 3038) >> 16 X2 = (-7357 * p) // 65536 return (p + (X1 + X2 + 3791) // 16) / 100 @property def altitude(self): ''' Altitude in m. ''' try: p = 44330 * (1.0 - math.pow(self.pressure / self._baseline, 0.1903)) except: p = 0.0 return p class BMP180(BMP085): def __init__(self, i2c=None): super().__init__(i2c)