rpi_envsens/dht.py

import adafruit_dht
import threading
import time

from . import logger


class dht_22(object):
    KEY_TEMPERATURE = 'temperature'
    KEY_HUMIDITY = 'humidity'
    KEY_TIME = 'time'

    def __init__(self, gpio, data_callback=None):
        self.__data_callback__ = data_callback
        # Initial the dht device, with data pin connected to:
        self.__dht_device__ = adafruit_dht.DHT22(gpio)
        self.__active__ = True
        self.__thread__ = threading.Thread(target=self.run, args=())
        self.__thread__.daemon = True                            # Daemonize thread
        self.__thread__.start()                                  # Start the execution

    def run(self):
        while self.__active__:
            data = self.__dht_data_transmission__()
            if data is not None:
                logger.debug('DHT-Communication: Successfully: %s', repr(data))
                if self.__data_callback__ is not None:
                    self.__data_callback__(**data)
            time.sleep(2.0)

    def close(self):
        self.__active__ = False
        self.__thread__.join()

    def __del__(self):
        self.close()

    def __dht_data_transmission__(self):
        while self.__active__:
            try:
                # Store the values
                data = {}
                data[self.KEY_TEMPERATURE] = self.__dht_device__.temperature
                data[self.KEY_HUMIDITY] = self.__dht_device__.humidity
                data[self.KEY_TIME] = time.time()
                if data[self.KEY_TEMPERATURE] is not None and data[self.KEY_HUMIDITY] is not None:
                    return data
                time.sleep(2.0)
            except RuntimeError as error:
                # Errors happen fairly often, DHT's are hard to read, just keep going
                logger.debug('DHT-Communication: ' + error.args[0])
                time.sleep(0.1)
            except Exception as error:
                self.__dht_device__.exit()
                raise error