bmp085.py

Go to the documentation of this file.

#   Copyright 2012-2013 Eric Ptak - trouch.com
#
#   Licensed under the Apache License, Version 2.0 (the "License");
#   you may not use this file except in compliance with the License.
#   You may obtain a copy of the License at
#
#       http://www.apache.org/licenses/LICENSE-2.0
#
#   Unless required by applicable law or agreed to in writing, software
#   distributed under the License is distributed on an "AS IS" BASIS,
#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#   See the License for the specific language governing permissions and
#   limitations under the License.

import time
from webiopi.utils.types import signInteger
from webiopi.devices.i2c import I2C
from webiopi.devices.sensor import Temperature, Pressure

class BMP085(I2C, Temperature, Pressure):
    def __init__(self, altitude=0, external=None):
        I2C.__init__(self, 0x77)
        Pressure.__init__(self, altitude, external)
        
        self.ac1 = self.readSignedInteger(0xAA)
        self.ac2 = self.readSignedInteger(0xAC)
        self.ac3 = self.readSignedInteger(0xAE)
        self.ac4 = self.readUnsignedInteger(0xB0)
        self.ac5 = self.readUnsignedInteger(0xB2)
        self.ac6 = self.readUnsignedInteger(0xB4)
        self.b1  = self.readSignedInteger(0xB6)
        self.b2  = self.readSignedInteger(0xB8)
        self.mb  = self.readSignedInteger(0xBA)
        self.mc  = self.readSignedInteger(0xBC)
        self.md  = self.readSignedInteger(0xBE)
        
    def __str__(self):
        return "BMP085"
    
    def __family__(self):
        return [Temperature.__family__(self), Pressure.__family__(self)]

    def readUnsignedInteger(self, address):
        d = self.readRegisters(address, 2)
        return d[0] << 8 | d[1]
    
    def readSignedInteger(self, address):
        d = self.readUnsignedInteger(address)
        return signInteger(d, 16)
    
    def readUT(self):
        self.writeRegister(0xF4, 0x2E)
        time.sleep(0.01)
        return self.readUnsignedInteger(0xF6)

    def readUP(self):
        self.writeRegister(0xF4, 0x34)
        time.sleep(0.01)
        return self.readUnsignedInteger(0xF6)

    def getB5(self):
        ut = self.readUT()
        x1 = ((ut - self.ac6) * self.ac5) / 2**15
        x2 = (self.mc * 2**11) / (x1 + self.md)
        return x1 + x2
    
    def __getKelvin__(self):
        return self.Celsius2Kelvin()

    def __getCelsius__(self):
        t = (self.getB5() + 8) / 2**4
        return float(t) / 10.0
    
    def __getFahrenheit__(self):
        return self.Celsius2Fahrenheit()

    def __getPascal__(self):
        b5 = self.getB5()
        up = self.readUP()
        b6 = b5 - 4000
        x1 = (self.b2 * (b6 * b6 / 2**12)) / 2**11
        x2 = self.ac2 * b6 / 2**11
        x3 = x1 + x2
        b3 = (self.ac1*4 + x3 + 2) / 4
        
        x1 = self.ac3 * b6 / 2**13
        x2 = (self.b1 * (b6 * b6 / 2**12)) / 2**16
        x3 = (x1 + x2 + 2) / 2**2
        b4 = self.ac4 * (x3 + 32768) / 2**15
        b7 = (up-b3) * 50000
        if b7 < 0x80000000:
            p = (b7 * 2) / b4
        else:
            p = (b7 / b4) * 2
        
        x1 = (p / 2**8) * (p / 2**8)
        x1 = (x1 * 3038) / 2**16
        x2 = (-7357*p) /  2**16
        p = p + (x1 + x2 + 3791) / 2**4
        return int(p)

class BMP180(BMP085):
    def __init__(self, altitude=0, external=None):
        BMP085.__init__(self, altitude, external)

    def __str__(self):
        return "BMP180"