gistfile1.py

#!/usr/bin/python
# -*- coding: utf-8 -*-

from smbus import SMBus
from pushetta import Pushetta

import math
import time


# Interfaccia generica per i sensori

class GenericSensor:

    def readValue(self):
        raise NotImplementedError('Metodo readValue da implementare')

    def measureUnit(self):
        raise NotImplementedError('Metodo measureUnit da implementare')


# Impementazione concreta per il sensore di temperatura

class TemperatureSensor(GenericSensor):

    adc_address = 0x48  # Address I2C
    adc_channel = 0x40  # Channel of device

    V_REF = 3.3  # Tensione riferimento misura ADC
    R1 = 15000.0  # Resistenza R1
    V_IN = 3.3  # Tensione alimentazione partitori tensione
    R_th0 = 10000.0  # Resistenza riferimento termistore a 25 c
    A = 0.00335402  # Steinhart-Hart Costante A
    B = 0.000256985  # Steinhart-Hart Costante B
    C = 2.62013e-6  # Steinhart-Hart Costante C
    D = 6.38309e-8  # Steinhart-Hart Costante D
    pB = 4100.0  # Costante parametro B
    K = 6.0  # Fattore dissipazione K 6mV C

    def readValue(self):
        bus = SMBus(1)  # 0 per le rev.1
        bus.write_byte(self.adc_address, self.adc_channel)
        raw_val = bus.read_byte(self.adc_address)
        raw_val = bus.read_byte(self.adc_address)
        raw_val = bus.read_byte(self.adc_address)

        V = raw_val * self.V_REF / 256.0
        R_th = self.R1 * V / (self.V_IN - V)

        # Calcolo dei gradi Kelvin con la formula di Steinhart-Hart

        logR = math.log(R_th / self.R_th0)
        logR2 = logR ** 2
        logR3 = logR ** 3
        Stein = 1.0 / (self.A + self.B * logR + self.C * logR2 + self.D
                       * logR3)

        # Conversione in Celsius

        Celsius = round(Stein - 273.15 - V ** 2 / (self.K * R_th), 2)

        return Celsius

    def measureUnit(self):
        return ' C'


pushetta = Pushetta('0011223344556677aabbccddeeff001122334455')
sensor = TemperatureSensor()
while True:
    temp = sensor.readValue()
    if temp < 18.0:
        pushetta.pushMessage('Camera', 'Brrrr...qui fa freddo')

    time.sleep(1)