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Copy pathAdafruit_BMP085.py
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Adafruit_BMP085.py
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#!/usr/bin/python
import time
from Adafruit_I2C import Adafruit_I2C
# ===========================================================================
# BMP085 Class
# ===========================================================================
class BMP085 :
i2c = None
# 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
__BMP085_READTEMPCMD = 0x2E
__BMP085_READPRESSURECMD = 0x34
# Private Fields
_cal_AC1 = 0
_cal_AC2 = 0
_cal_AC3 = 0
_cal_AC4 = 0
_cal_AC5 = 0
_cal_AC6 = 0
_cal_B1 = 0
_cal_B2 = 0
_cal_MB = 0
_cal_MC = 0
_cal_MD = 0
# Constructor
def __init__(self, address=0x77, mode=1, debug=False):
self.i2c = Adafruit_I2C(address)
self.address = address
self.debug = debug
# Make sure the specified mode is in the appropriate range
if ((mode < 0) | (mode > 3)):
if (self.debug):
print "Invalid Mode: Using STANDARD by default"
self.mode = self.__BMP085_STANDARD
else:
self.mode = mode
# Read the calibration data
self.readCalibrationData()
def readCalibrationData(self):
"Reads the calibration data from the IC"
self._cal_AC1 = self.i2c.readS16(self.__BMP085_CAL_AC1) # INT16
self._cal_AC2 = self.i2c.readS16(self.__BMP085_CAL_AC2) # INT16
self._cal_AC3 = self.i2c.readS16(self.__BMP085_CAL_AC3) # INT16
self._cal_AC4 = self.i2c.readU16(self.__BMP085_CAL_AC4) # UINT16
self._cal_AC5 = self.i2c.readU16(self.__BMP085_CAL_AC5) # UINT16
self._cal_AC6 = self.i2c.readU16(self.__BMP085_CAL_AC6) # UINT16
self._cal_B1 = self.i2c.readS16(self.__BMP085_CAL_B1) # INT16
self._cal_B2 = self.i2c.readS16(self.__BMP085_CAL_B2) # INT16
self._cal_MB = self.i2c.readS16(self.__BMP085_CAL_MB) # INT16
self._cal_MC = self.i2c.readS16(self.__BMP085_CAL_MC) # INT16
self._cal_MD = self.i2c.readS16(self.__BMP085_CAL_MD) # INT16
if (self.debug):
self.showCalibrationData()
def showCalibrationData(self):
"Displays the calibration values for debugging purposes"
print "DBG: AC1 = %6d" % (self._cal_AC1)
print "DBG: AC2 = %6d" % (self._cal_AC2)
print "DBG: AC3 = %6d" % (self._cal_AC3)
print "DBG: AC4 = %6d" % (self._cal_AC4)
print "DBG: AC5 = %6d" % (self._cal_AC5)
print "DBG: AC6 = %6d" % (self._cal_AC6)
print "DBG: B1 = %6d" % (self._cal_B1)
print "DBG: B2 = %6d" % (self._cal_B2)
print "DBG: MB = %6d" % (self._cal_MB)
print "DBG: MC = %6d" % (self._cal_MC)
print "DBG: MD = %6d" % (self._cal_MD)
def readRawTemp(self):
"Reads the raw (uncompensated) temperature from the sensor"
self.i2c.write8(self.__BMP085_CONTROL, self.__BMP085_READTEMPCMD)
time.sleep(0.005) # Wait 5ms
raw = self.i2c.readU16(self.__BMP085_TEMPDATA)
if (self.debug):
print "DBG: Raw Temp: 0x%04X (%d)" % (raw & 0xFFFF, raw)
return raw
def readRawPressure(self):
"Reads the raw (uncompensated) pressure level from the sensor"
self.i2c.write8(self.__BMP085_CONTROL, self.__BMP085_READPRESSURECMD + (self.mode << 6))
if (self.mode == self.__BMP085_ULTRALOWPOWER):
time.sleep(0.005)
elif (self.mode == self.__BMP085_HIGHRES):
time.sleep(0.014)
elif (self.mode == self.__BMP085_ULTRAHIGHRES):
time.sleep(0.026)
else:
time.sleep(0.008)
msb = self.i2c.readU8(self.__BMP085_PRESSUREDATA)
lsb = self.i2c.readU8(self.__BMP085_PRESSUREDATA+1)
xlsb = self.i2c.readU8(self.__BMP085_PRESSUREDATA+2)
raw = ((msb << 16) + (lsb << 8) + xlsb) >> (8 - self.mode)
if (self.debug):
print "DBG: Raw Pressure: 0x%04X (%d)" % (raw & 0xFFFF, raw)
return raw
def readTemperature(self):
"Gets the compensated temperature in degrees celcius"
UT = 0
X1 = 0
X2 = 0
B5 = 0
temp = 0.0
# Read raw temp before aligning it with the calibration values
UT = self.readRawTemp()
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
if (self.debug):
print "DBG: Calibrated temperature = %f C" % temp
return temp
def readPressure(self):
"Gets the compensated pressure in pascal"
UT = 0
UP = 0
B3 = 0
B5 = 0
B6 = 0
X1 = 0
X2 = 0
X3 = 0
p = 0
B4 = 0
B7 = 0
UT = self.readRawTemp()
UP = self.readRawPressure()
# You can use the datasheet values to test the conversion results
# dsValues = True
dsValues = False
if (dsValues):
UT = 27898
UP = 23843
self._cal_AC6 = 23153
self._cal_AC5 = 32757
self._cal_MC = -8711
self._cal_MD = 2868
self._cal_B1 = 6190
self._cal_B2 = 4
self._cal_AC3 = -14383
self._cal_AC2 = -72
self._cal_AC1 = 408
self._cal_AC4 = 32741
self.mode = self.__BMP085_ULTRALOWPOWER
if (self.debug):
self.showCalibrationData()
# True Temperature Calculations
X1 = ((UT - self._cal_AC6) * self._cal_AC5) >> 15
X2 = (self._cal_MC << 11) / (X1 + self._cal_MD)
B5 = X1 + X2
if (self.debug):
print "DBG: X1 = %d" % (X1)
print "DBG: X2 = %d" % (X2)
print "DBG: B5 = %d" % (B5)
print "DBG: True Temperature = %.2f C" % (((B5 + 8) >> 4) / 10.0)
# Pressure Calculations
B6 = B5 - 4000
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
if (self.debug):
print "DBG: B6 = %d" % (B6)
print "DBG: X1 = %d" % (X1)
print "DBG: X2 = %d" % (X2)
print "DBG: B3 = %d" % (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
B7 = (UP - B3) * (50000 >> self.mode)
if (self.debug):
print "DBG: X1 = %d" % (X1)
print "DBG: X2 = %d" % (X2)
print "DBG: B4 = %d" % (B4)
print "DBG: B7 = %d" % (B7)
if (B7 < 0x80000000):
p = (B7 * 2) / B4
else:
p = (B7 / B4) * 2
X1 = (p >> 8) * (p >> 8)
X1 = (X1 * 3038) >> 16
X2 = (-7375 * p) >> 16
if (self.debug):
print "DBG: p = %d" % (p)
print "DBG: X1 = %d" % (X1)
print "DBG: X2 = %d" % (X2)
p = p + ((X1 + X2 + 3791) >> 4)
if (self.debug):
print "DBG: Pressure = %d Pa" % (p)
return p
def readAltitude(self, seaLevelPressure=101325):
"Calculates the altitude in meters"
altitude = 0.0
pressure = float(self.readPressure())
altitude = 44330.0 * (1.0 - pow(pressure / seaLevelPressure, 0.1903))
if (self.debug):
print "DBG: Altitude = %d" % (altitude)
return altitude
return 0