''' bmp180 is a micropython module for the Bosch BMP180 sensor. It measures temperature as well as pressure, with a high enough resolution to calculate altitude. Breakoutboard: http://www.adafruit.com/products/1603 data-sheet: http://ae-bst.resource.bosch.com/media/products/dokumente/ bmp180/BST-BMP180-DS000-09.pdf The MIT License (MIT) Copyright (c) 2014 Sebastian Plamauer, oeplse@gmail.com 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 from machine import I2C, Pin import math import time # BMP180 class class BMP180(): ''' Module for the BMP180 pressure sensor. ''' _bmp_addr = 119 # adress of BMP180 is hardcoded on the sensor # init def __init__(self, i2c_bus): # create i2c obect _bmp_addr = self._bmp_addr self._bmp_i2c = i2c_bus self._bmp_i2c.start() self.chip_id = self._bmp_i2c.readfrom_mem(_bmp_addr, 0xD0, 2) # read calibration data from EEPROM self._AC1 = unp('>h', self._bmp_i2c.readfrom_mem(_bmp_addr, 0xAA, 2))[0] self._AC2 = unp('>h', self._bmp_i2c.readfrom_mem(_bmp_addr, 0xAC, 2))[0] self._AC3 = unp('>h', self._bmp_i2c.readfrom_mem(_bmp_addr, 0xAE, 2))[0] self._AC4 = unp('>H', self._bmp_i2c.readfrom_mem(_bmp_addr, 0xB0, 2))[0] self._AC5 = unp('>H', self._bmp_i2c.readfrom_mem(_bmp_addr, 0xB2, 2))[0] self._AC6 = unp('>H', self._bmp_i2c.readfrom_mem(_bmp_addr, 0xB4, 2))[0] self._B1 = unp('>h', self._bmp_i2c.readfrom_mem(_bmp_addr, 0xB6, 2))[0] self._B2 = unp('>h', self._bmp_i2c.readfrom_mem(_bmp_addr, 0xB8, 2))[0] self._MB = unp('>h', self._bmp_i2c.readfrom_mem(_bmp_addr, 0xBA, 2))[0] self._MC = unp('>h', self._bmp_i2c.readfrom_mem(_bmp_addr, 0xBC, 2))[0] self._MD = unp('>h', self._bmp_i2c.readfrom_mem(_bmp_addr, 0xBE, 2))[0] # settings to be adjusted by user self.oversample_setting = 3 self.baseline = 101325.0 # output raw self.UT_raw = None self.B5_raw = None self.MSB_raw = None self.LSB_raw = None self.XLSB_raw = None 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_setting] # gauge raw def makegauge(self): ''' Generator refreshing the raw measurments. ''' delays = (5, 8, 14, 25) while True: self._bmp_i2c.writeto_mem(self._bmp_addr, 0xF4, bytearray([0x2E])) t_start = time.ticks_ms() while (time.ticks_ms() - t_start) <= 5: # 5mS delay yield None try: self.UT_raw = self._bmp_i2c.readfrom_mem(self._bmp_addr, 0xF6, 2) except: yield None self._bmp_i2c.writeto_mem(self._bmp_addr, 0xF4, bytearray([0x34+(self.oversample_setting << 6)])) t_pressure_ready = delays[self.oversample_setting] t_start = time.ticks_ms() while (time.ticks_ms() - t_start) <= t_pressure_ready: yield None try: self.MSB_raw = self._bmp_i2c.readfrom_mem(self._bmp_addr, 0xF6, 1) self.LSB_raw = self._bmp_i2c.readfrom_mem(self._bmp_addr, 0xF7, 1) self.XLSB_raw = self._bmp_i2c.readfrom_mem(self._bmp_addr, 0xF8, 1) 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 oversample_sett(self): return self.oversample_setting @oversample_sett.setter def oversample_sett(self, value): if value in range(4): self.oversample_setting = value else: print('oversample_sett can only be 0, 1, 2 or 3, using 3 instead') self.oversample_setting = 3 @property def temperature(self): ''' Temperature in degree C. ''' next(self.gauge) try: UT = unp('>H', self.UT_raw)[0] except: return 0.0 X1 = (UT-self._AC6)*self._AC5/2**15 X2 = self._MC*2**11/(X1+self._MD) self.B5_raw = X1+X2 return (((X1+X2)+8)/2**4)/10 @property def pressure(self): ''' Pressure in mbar. ''' next(self.gauge) self.temperature # Populate self.B5_raw try: MSB = unp('B', self.MSB_raw)[0] LSB = unp('B', self.LSB_raw)[0] XLSB = unp('B', self.XLSB_raw)[0] except: return 0.0 UP = ((MSB << 16)+(LSB << 8)+XLSB) >> (8-self.oversample_setting) B6 = self.B5_raw-4000 X1 = (self._B2*(B6**2/2**12))/2**11 X2 = self._AC2*B6/2**11 X3 = X1+X2 B3 = ((int((self._AC1*4+X3)) << self.oversample_setting)+2)/4 X1 = self._AC3*B6/2**13 X2 = (self._B1*(B6**2/2**12))/2**16 X3 = ((X1+X2)+2)/2**2 B4 = abs(self._AC4)*(X3+32768)/2**15 B7 = (abs(UP)-B3) * (50000 >> self.oversample_setting) if B7 < 0x80000000: pressure = (B7*2)/B4 else: pressure = (B7/B4)*2 X1 = (pressure/2**8)**2 X1 = (X1*3038)/2**16 X2 = (-7357*pressure)/2**16 return pressure+(X1+X2+3791)/2**4 @property def altitude(self): ''' Altitude in m. ''' try: p = -7990.0*math.log(self.pressure/self.baseline) except: p = 0.0 return p