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5559f4c Apr 14, 2016
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# Copyright (c) 2014 Adafruit Industries
# Author: Tony DiCola
#
# 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 __future__ import division
import logging
import time
# BMP085 default address.
BMP085_I2CADDR = 0x77
# Operating Modes
BMP085_ULTRALOWPOWER = 0
BMP085_STANDARD = 1
BMP085_HIGHRES = 2
BMP085_ULTRAHIGHRES = 3
# BMP085 Registers
BMP085_CAL_AC1 = 0xAA # R Calibration data (16 bits)
BMP085_CAL_AC2 = 0xAC # R Calibration data (16 bits)
BMP085_CAL_AC3 = 0xAE # R Calibration data (16 bits)
BMP085_CAL_AC4 = 0xB0 # R Calibration data (16 bits)
BMP085_CAL_AC5 = 0xB2 # R Calibration data (16 bits)
BMP085_CAL_AC6 = 0xB4 # R Calibration data (16 bits)
BMP085_CAL_B1 = 0xB6 # R Calibration data (16 bits)
BMP085_CAL_B2 = 0xB8 # R Calibration data (16 bits)
BMP085_CAL_MB = 0xBA # R Calibration data (16 bits)
BMP085_CAL_MC = 0xBC # R Calibration data (16 bits)
BMP085_CAL_MD = 0xBE # R Calibration data (16 bits)
BMP085_CONTROL = 0xF4
BMP085_TEMPDATA = 0xF6
BMP085_PRESSUREDATA = 0xF6
# Commands
BMP085_READTEMPCMD = 0x2E
BMP085_READPRESSURECMD = 0x34
class BMP085(object):
def __init__(self, mode=BMP085_STANDARD, address=BMP085_I2CADDR, i2c=None, **kwargs):
self._logger = logging.getLogger('Adafruit_BMP.BMP085')
# Check that mode is valid.
if mode not in [BMP085_ULTRALOWPOWER, BMP085_STANDARD, BMP085_HIGHRES, BMP085_ULTRAHIGHRES]:
raise ValueError('Unexpected mode value {0}. Set mode to one of BMP085_ULTRALOWPOWER, BMP085_STANDARD, BMP085_HIGHRES, or BMP085_ULTRAHIGHRES'.format(mode))
self._mode = mode
# Create I2C device.
if i2c is None:
import Adafruit_GPIO.I2C as I2C
i2c = I2C
self._device = i2c.get_i2c_device(address, **kwargs)
# Load calibration values.
self._load_calibration()
def _load_calibration(self):
self.cal_AC1 = self._device.readS16BE(BMP085_CAL_AC1) # INT16
self.cal_AC2 = self._device.readS16BE(BMP085_CAL_AC2) # INT16
self.cal_AC3 = self._device.readS16BE(BMP085_CAL_AC3) # INT16
self.cal_AC4 = self._device.readU16BE(BMP085_CAL_AC4) # UINT16
self.cal_AC5 = self._device.readU16BE(BMP085_CAL_AC5) # UINT16
self.cal_AC6 = self._device.readU16BE(BMP085_CAL_AC6) # UINT16
self.cal_B1 = self._device.readS16BE(BMP085_CAL_B1) # INT16
self.cal_B2 = self._device.readS16BE(BMP085_CAL_B2) # INT16
self.cal_MB = self._device.readS16BE(BMP085_CAL_MB) # INT16
self.cal_MC = self._device.readS16BE(BMP085_CAL_MC) # INT16
self.cal_MD = self._device.readS16BE(BMP085_CAL_MD) # INT16
self._logger.debug('AC1 = {0:6d}'.format(self.cal_AC1))
self._logger.debug('AC2 = {0:6d}'.format(self.cal_AC2))
self._logger.debug('AC3 = {0:6d}'.format(self.cal_AC3))
self._logger.debug('AC4 = {0:6d}'.format(self.cal_AC4))
self._logger.debug('AC5 = {0:6d}'.format(self.cal_AC5))
self._logger.debug('AC6 = {0:6d}'.format(self.cal_AC6))
self._logger.debug('B1 = {0:6d}'.format(self.cal_B1))
self._logger.debug('B2 = {0:6d}'.format(self.cal_B2))
self._logger.debug('MB = {0:6d}'.format(self.cal_MB))
self._logger.debug('MC = {0:6d}'.format(self.cal_MC))
self._logger.debug('MD = {0:6d}'.format(self.cal_MD))
def _load_datasheet_calibration(self):
# Set calibration from values in the datasheet example. Useful for debugging the
# temp and pressure calculation accuracy.
self.cal_AC1 = 408
self.cal_AC2 = -72
self.cal_AC3 = -14383
self.cal_AC4 = 32741
self.cal_AC5 = 32757
self.cal_AC6 = 23153
self.cal_B1 = 6190
self.cal_B2 = 4
self.cal_MB = -32767
self.cal_MC = -8711
self.cal_MD = 2868
def read_raw_temp(self):
"""Reads the raw (uncompensated) temperature from the sensor."""
self._device.write8(BMP085_CONTROL, BMP085_READTEMPCMD)
time.sleep(0.005) # Wait 5ms
raw = self._device.readU16BE(BMP085_TEMPDATA)
self._logger.debug('Raw temp 0x{0:X} ({1})'.format(raw & 0xFFFF, raw))
return raw
def read_raw_pressure(self):
"""Reads the raw (uncompensated) pressure level from the sensor."""
self._device.write8(BMP085_CONTROL, BMP085_READPRESSURECMD + (self._mode << 6))
if self._mode == BMP085_ULTRALOWPOWER:
time.sleep(0.005)
elif self._mode == BMP085_HIGHRES:
time.sleep(0.014)
elif self._mode == BMP085_ULTRAHIGHRES:
time.sleep(0.026)
else:
time.sleep(0.008)
msb = self._device.readU8(BMP085_PRESSUREDATA)
lsb = self._device.readU8(BMP085_PRESSUREDATA+1)
xlsb = self._device.readU8(BMP085_PRESSUREDATA+2)
raw = ((msb << 16) + (lsb << 8) + xlsb) >> (8 - self._mode)
self._logger.debug('Raw pressure 0x{0:04X} ({1})'.format(raw & 0xFFFF, raw))
return raw
def read_temperature(self):
"""Gets the compensated temperature in degrees celsius."""
UT = self.read_raw_temp()
# Datasheet value for debugging:
#UT = 27898
# Calculations below are taken straight from section 3.5 of the datasheet.
X1 = ((UT - self.cal_AC6) * self.cal_AC5) >> 15
X2 = (self.cal_MC << 11) // (X1 + self.cal_MD)
B5 = X1 + X2
temp = ((B5 + 8) >> 4) / 10.0
self._logger.debug('Calibrated temperature {0} C'.format(temp))
return temp
def read_pressure(self):
"""Gets the compensated pressure in Pascals."""
UT = self.read_raw_temp()
UP = self.read_raw_pressure()
# Datasheet values for debugging:
#UT = 27898
#UP = 23843
# Calculations below are taken straight from section 3.5 of the datasheet.
# Calculate true temperature coefficient B5.
X1 = ((UT - self.cal_AC6) * self.cal_AC5) >> 15
X2 = (self.cal_MC << 11) // (X1 + self.cal_MD)
B5 = X1 + X2
self._logger.debug('B5 = {0}'.format(B5))
# Pressure Calculations
B6 = B5 - 4000
self._logger.debug('B6 = {0}'.format(B6))
X1 = (self.cal_B2 * (B6 * B6) >> 12) >> 11
X2 = (self.cal_AC2 * B6) >> 11
X3 = X1 + X2
B3 = (((self.cal_AC1 * 4 + X3) << self._mode) + 2) // 4
self._logger.debug('B3 = {0}'.format(B3))
X1 = (self.cal_AC3 * B6) >> 13
X2 = (self.cal_B1 * ((B6 * B6) >> 12)) >> 16
X3 = ((X1 + X2) + 2) >> 2
B4 = (self.cal_AC4 * (X3 + 32768)) >> 15
self._logger.debug('B4 = {0}'.format(B4))
B7 = (UP - B3) * (50000 >> self._mode)
self._logger.debug('B7 = {0}'.format(B7))
if B7 < 0x80000000:
p = (B7 * 2) // B4
else:
p = (B7 // B4) * 2
X1 = (p >> 8) * (p >> 8)
X1 = (X1 * 3038) >> 16
X2 = (-7357 * p) >> 16
p = p + ((X1 + X2 + 3791) >> 4)
self._logger.debug('Pressure {0} Pa'.format(p))
return p
def read_altitude(self, sealevel_pa=101325.0):
"""Calculates the altitude in meters."""
# Calculation taken straight from section 3.6 of the datasheet.
pressure = float(self.read_pressure())
altitude = 44330.0 * (1.0 - pow(pressure / sealevel_pa, (1.0/5.255)))
self._logger.debug('Altitude {0} m'.format(altitude))
return altitude
def read_sealevel_pressure(self, altitude_m=0.0):
"""Calculates the pressure at sealevel when given a known altitude in
meters. Returns a value in Pascals."""
pressure = float(self.read_pressure())
p0 = pressure / pow(1.0 - altitude_m/44330.0, 5.255)
self._logger.debug('Sealevel pressure {0} Pa'.format(p0))
return p0