Migrated sensor.bme280 to the new SensorPlugin interface.

Removed the old `backend.sensor.bme280` and the old `gpio.sensor.bme280`
plugin. They have now been merged into the new `sensor.bme280` runnable
plugin, which extends the `SensorPlugin` API and supports entities.

README.md

@@ -8,8 +8,6 @@ Platypush
 [![Last Commit](https://img.shields.io/github/last-commit/BlackLight/platypush.svg)](https://git.platypush.tech/platypush/platypush/-/commits/master/)
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 <!-- toc -->
 

platypush/backend/sensor/__init__.py

@@ -1,232 +0,0 @@
-import time
-
-from platypush.backend import Backend
-from platypush.context import get_plugin
-from platypush.message.event.sensor import SensorDataChangeEvent, \
-    SensorDataAboveThresholdEvent, SensorDataBelowThresholdEvent
-
-
-class SensorBackend(Backend):
-    """
-    Abstract backend for polling sensors.
-
-    Triggers:
-
-        * :class:`platypush.message.event.sensor.SensorDataChangeEvent` if the measurements of a sensor have changed
-        * :class:`platypush.message.event.sensor.SensorDataAboveThresholdEvent` if the measurements of a sensor have
-            gone above a configured threshold
-        * :class:`platypush.message.event.sensor.SensorDataBelowThresholdEvent` if the measurements of a sensor have
-            gone below a configured threshold
-
-    """
-
-    default_tolerance = 1e-7
-
-    def __init__(self, plugin=None, plugin_args=None, thresholds=None, tolerance=default_tolerance, poll_seconds=None,
-                 enabled_sensors=None, **kwargs):
-        """
-        :param plugin: If set, then this plugin instance, referenced by plugin id, will be polled
-            through ``get_plugin()``. Example: ``'gpio.sensor.bme280'`` or ``'gpio.sensor.envirophat'``.
-        :type plugin: str
-
-        :param plugin_args: If plugin is set and its ``get_measurement()`` method accepts optional arguments, then you
-            can pass those arguments through ``plugin_args``.
-        :type plugin_args: dict
-
-        :param thresholds: Thresholds can be either a scalar value or a dictionary (e.g. ``{"temperature": 20.0}``).
-            Sensor threshold events will be fired when measurements get above or below these values.
-            Set it as a scalar if your get_measurement() code returns a scalar, as a dictionary if it returns a
-            dictionary of values.  For instance, if your sensor code returns both humidity and temperature in a format
-            like ``{'humidity':60.0, 'temperature': 25.0}``, you'll want to set up a threshold on temperature with a
-            syntax like ``{'temperature':20.0}`` to trigger events when the temperature goes above/below 20 degrees.
-
-        :param tolerance: If set, then the sensor change events will be triggered only if the difference between
-            the new value and the previous value is higher than the specified tolerance. Example::
-
-                {
-                    "temperature": 0.01,  # Tolerance on the 2nd decimal digit
-                    "humidity": 0.1       # Tolerance on the 1st decimal digit
-                }
-
-        :type tolerance: dict or float
-
-        :param poll_seconds: If set, the thread will wait for the specified number of seconds between a read and the
-            next one.
-        :type poll_seconds: float
-
-        :param enabled_sensors: If ``get_measurement()`` returns data in dict form, then ``enabled_sensors`` selects
-            which keys should be taken into account when monitoring for new events (e.g. "temperature" or "humidity").
-        :type enabled_sensors: dict (in the form ``name -> [True/False]``), set or list
-        """
-
-        super().__init__(**kwargs)
-
-        self.data = None
-        self.plugin = plugin
-        self.plugin_args = plugin_args or {}
-        self.thresholds = thresholds
-        self.tolerance = tolerance
-        self.poll_seconds = poll_seconds
-
-        if isinstance(enabled_sensors, list):
-            enabled_sensors = set(enabled_sensors)
-        if isinstance(enabled_sensors, set):
-            enabled_sensors = {k: True for k in enabled_sensors}
-
-        self.enabled_sensors = enabled_sensors or {}
-
-    def get_measurement(self):
-        """
-        Wrapper around ``plugin.get_measurement()`` that can filter events on specified enabled sensors data or on
-        specified tolerance values. It can be overridden by derived classes.
-        """
-        if not self.plugin:
-            raise NotImplementedError('No plugin specified')
-
-        reload = False
-        success = False
-        data = None
-
-        while not success:
-            try:
-                plugin = get_plugin(self.plugin, reload=reload)
-                data = plugin.get_data(**self.plugin_args).output
-                if reload:
-                    self.logger.info('Backend successfully restored')
-
-                success = True
-            except Exception as e:
-                self.logger.warning('Unexpected exception while getting data: {}'.format(str(e)))
-                self.logger.exception(e)
-                reload = True
-                time.sleep(5)
-
-            if self.enabled_sensors and data is not None:
-                data = {
-                    sensor: data[sensor]
-                    for sensor, enabled in self.enabled_sensors.items()
-                    if enabled and sensor in data
-                }
-
-        return data
-
-    @staticmethod
-    def _get_value(value):
-        if isinstance(value, float) or isinstance(value, int) or isinstance(value, bool):
-            return value
-        return float(value)
-
-    def get_new_data(self, new_data):
-        if self.data is None or new_data is None:
-            return new_data
-
-        try:
-            # Scalar data case
-            new_data = self._get_value(new_data)
-            return new_data if abs(new_data - self.data) >= self.tolerance else None
-        except (ValueError, TypeError):
-            # If it's not a scalar then it should be a dict
-            assert isinstance(new_data, dict), 'Invalid type {} received for sensor data'.format(type(new_data))
-
-        ret = {}
-        for k, v in new_data.items():
-            if (v is None and self.data.get(k) is not None) \
-                    or k not in self.data \
-                    or self.tolerance is None:
-                ret[k] = v
-                continue
-
-            if v is None:
-                continue
-
-            tolerance = None
-            is_nan = False
-            old_v = None
-
-            try:
-                v = self._get_value(v)
-                old_v = self._get_value(self.data.get(k))
-            except (TypeError, ValueError):
-                is_nan = True
-
-            if not is_nan:
-                if isinstance(self.tolerance, dict):
-                    tolerance = float(self.tolerance.get(k, self.default_tolerance))
-                else:
-                    try:
-                        tolerance = float(self.tolerance)
-                    except (TypeError, ValueError):
-                        pass
-
-                if tolerance is None or abs(v - old_v) >= tolerance:
-                    ret[k] = v
-            elif k not in self.data or self.data[k] != v:
-                ret[k] = v
-
-        return ret
-
-    def on_stop(self):
-        super().on_stop()
-        if not self.plugin:
-            return
-
-        plugin = get_plugin(self.plugin)
-        if plugin and hasattr(plugin, 'close'):
-            plugin.close()
-
-    def process_data(self, data, new_data=None, **__):
-        if data is not None and data not in ({}, []):
-            self.bus.post(SensorDataChangeEvent(data=data, source=self.plugin or self.__class__.__name__))
-
-    def run(self):
-        super().run()
-        self.logger.info('Initialized {} sensor backend'.format(self.__class__.__name__))
-
-        while not self.should_stop():
-            try:
-                data = self.get_measurement()
-                new_data = self.get_new_data(data)
-                self.process_data(new_data)
-
-                data_below_threshold = {}
-                data_above_threshold = {}
-
-                if self.thresholds:
-                    if isinstance(self.thresholds, dict) and isinstance(data, dict):
-                        for (measure, thresholds) in self.thresholds.items():
-                            if measure not in data:
-                                continue
-
-                            if not isinstance(thresholds, list):
-                                thresholds = [thresholds]
-
-                            for threshold in thresholds:
-                                if data[measure] > threshold and (self.data is None or (
-                                        measure in self.data and self.data[measure] <= threshold)):
-                                    data_above_threshold[measure] = data[measure]
-                                elif data[measure] < threshold and (self.data is None or (
-                                        measure in self.data and self.data[measure] >= threshold)):
-                                    data_below_threshold[measure] = data[measure]
-
-                if data_below_threshold:
-                    self.bus.post(SensorDataBelowThresholdEvent(data=data_below_threshold))
-
-                if data_above_threshold:
-                    self.bus.post(SensorDataAboveThresholdEvent(data=data_above_threshold))
-
-                self.data = data
-
-                if new_data:
-                    if isinstance(new_data, dict):
-                        for k, v in new_data.items():
-                            self.data[k] = v
-                    else:
-                        self.data = new_data
-            except Exception as e:
-                self.logger.exception(e)
-
-            if self.poll_seconds:
-                time.sleep(self.poll_seconds)
-
-
-# vim:sw=4:ts=4:et:

platypush/backend/sensor/bme280/__init__.py

@@ -1,39 +0,0 @@
-from platypush.backend.sensor import SensorBackend
-
-
-class SensorBme280Backend(SensorBackend):
-    """
-    Backend to poll analog sensor values from a `BME280 <https://shop.pimoroni.com/products/bme280-breakout>`_
-    environment sensor
-
-    Requires:
-
-        * ``pimoroni-bme280`` (``pip install pimoroni-bme280``)
-
-    Triggers:
-
-        * :class:`platypush.message.event.sensor.SensorDataChangeEvent` if the measurements of a sensor have changed
-        * :class:`platypush.message.event.sensor.SensorDataAboveThresholdEvent` if the measurements of a sensor have
-            gone above a configured threshold
-        * :class:`platypush.message.event.sensor.SensorDataBelowThresholdEvent` if the measurements of a sensor have
-            gone below a configured threshold
-
-    """
-
-    def __init__(self, temperature=True, pressure=True, humidity=True, **kwargs):
-        """
-        :param temperature: Enable temperature sensor polling
-        :param pressure: Enable pressure sensor polling
-        :param humidity: Enable humidity sensor polling
-        """
-
-        enabled_sensors = {
-            'temperature': temperature,
-            'pressure': pressure,
-            'humidity': humidity,
-        }
-
-        super().__init__(plugin='gpio.sensor.bme280', enabled_sensors=enabled_sensors, **kwargs)
-
-
-# vim:sw=4:ts=4:et:

platypush/backend/sensor/bme280/manifest.yaml

@@ -1,13 +0,0 @@
-manifest:
-  events:
-    platypush.message.event.sensor.SensorDataAboveThresholdEvent: if the measurements
-      of a sensor havegone above a configured threshold
-    platypush.message.event.sensor.SensorDataBelowThresholdEvent: if the measurements
-      of a sensor havegone below a configured threshold
-    platypush.message.event.sensor.SensorDataChangeEvent: if the measurements of a
-      sensor have changed
-  install:
-    pip:
-    - pimoroni-bme280
-  package: platypush.backend.sensor.bme280
-  type: backend

platypush/backend/sensor/serial/__init__.py

@@ -1,27 +0,0 @@
-from platypush.backend.sensor import SensorBackend
-
-
-class SensorSerialBackend(SensorBackend):
-    """
-    This backend listens for new events from sensors connected through a serial
-    interface (like Arduino) acting as a wrapper for the ``serial`` plugin.
-
-    Requires:
-
-        * The :mod:`platypush.plugins.serial` plugin configured
-
-    Triggers:
-
-        * :class:`platypush.message.event.sensor.SensorDataChangeEvent` if the measurements of a sensor have changed
-        * :class:`platypush.message.event.sensor.SensorDataAboveThresholdEvent` if the measurements of a sensor have
-            gone above a configured threshold
-        * :class:`platypush.message.event.sensor.SensorDataBelowThresholdEvent` if the measurements of a sensor have
-            gone below a configured threshold
-
-    """
-
-    def __init__(self, **kwargs):
-        super().__init__(plugin='serial', **kwargs)
-
-
-# vim:sw=4:ts=4:et:

platypush/backend/sensor/serial/manifest.yaml

@@ -1,12 +0,0 @@
-manifest:
-  events:
-    platypush.message.event.sensor.SensorDataAboveThresholdEvent: if the measurements
-      of a sensor havegone above a configured threshold
-    platypush.message.event.sensor.SensorDataBelowThresholdEvent: if the measurements
-      of a sensor havegone below a configured threshold
-    platypush.message.event.sensor.SensorDataChangeEvent: if the measurements of a
-      sensor have changed
-  install:
-    pip: []
-  package: platypush.backend.sensor.serial
-  type: backend

platypush/common/sensors.py

@@ -0,0 +1,11 @@
+from typing import Iterable, Mapping, Union
+
+Numeric = Union[float, int]
+SensorDataType = Union[Numeric, Mapping[str, Numeric], Iterable[Numeric]]
+"""
+Numeric sensor data published by integrations can be either of:
+
+    - ``int``/``float``
+    - Mapping of ``str -> int/float``
+    - List of ``int``/``float``
+"""

platypush/message/event/sensor/__init__.py

@@ -1,49 +1,41 @@
+from abc import ABC
 from typing import Optional
 
+from platypush.common.sensors import SensorDataType
 from platypush.message.event import Event
 
 
-class SensorDataChangeEvent(Event):
+class SensorDataEvent(Event, ABC):
+    """
+    Sensor events base class.
+    """
+
+    def __init__(
+        self, *args, data: SensorDataType, source: Optional[str] = None, **kwargs
+    ):
+        """
+        :param data: Sensor data.
+        :param source: Sensor source - usually the plugin qualified name.
+        """
+        super().__init__(data=data, source=source, *args, **kwargs)
+
+
+class SensorDataChangeEvent(SensorDataEvent):
     """
     Event triggered when a sensor has new data
     """
 
-    def __init__(self, data, source: Optional[str] = None, *args, **kwargs):
-        """
-        :param data: Sensor data
-        """
 
-        super().__init__(data=data, source=source, *args, **kwargs)
+class SensorDataAboveThresholdEvent(SensorDataEvent):
-        self.data = data
-        self.source = source
-
-
-class SensorDataAboveThresholdEvent(Event):
     """
     Event triggered when a sensor's read goes above a configured threshold
     """
 
-    def __init__(self, data, *args, **kwargs):
-        """
-        :param data: Sensor data
-        """
 
-        super().__init__(data=data, *args, **kwargs)
+class SensorDataBelowThresholdEvent(SensorDataEvent):
-        self.data = data
-
-
-class SensorDataBelowThresholdEvent(Event):
     """
     Event triggered when a sensor's read goes below a configured threshold
     """
 
-    def __init__(self, data, *args, **kwargs):
-        """
-        :param data: Sensor data
-        """
-
-        super().__init__(data=data, *args, **kwargs)
-        self.data = data
-
 
 # vim:sw=4:ts=4:et:

platypush/plugins/__init__.py

@@ -1,6 +1,7 @@
 import asyncio
 import logging
 import threading
+import warnings
 
 from abc import ABC, abstractmethod
 from functools import wraps
@@ -86,7 +87,9 @@ class RunnablePlugin(Plugin):
     ):
         """
         :param poll_interval: How often the :meth:`.loop` function should be
-            execute (default: 15 seconds).
+            execute (default: 15 seconds). *NOTE*: For back-compatibility
+            reasons, the `poll_seconds` argument is also supported, but it's
+            deprecated.
         :param stop_timeout: How long we should wait for any running
             threads/processes to stop before exiting (default: 5 seconds).
         """
@@ -97,6 +100,16 @@ class RunnablePlugin(Plugin):
         self._stop_timeout = stop_timeout
         self._thread: Optional[threading.Thread] = None
 
+        if kwargs.get('poll_seconds') is not None:
+            warnings.warn(
+                'poll_seconds is deprecated, use poll_interval instead',
+                DeprecationWarning,
+                stacklevel=2,
+            )
+
+            if self.poll_interval is None:
+                self.poll_interval = kwargs['poll_seconds']
+
     def main(self):
         """
         Implementation of the main loop of the plugin.

platypush/plugins/gpio/sensor/bme280/__init__.py

@@ -1,63 +0,0 @@
-from platypush.plugins import action
-from platypush.plugins.gpio.sensor import GpioSensorPlugin
-
-
-class GpioSensorBme280Plugin(GpioSensorPlugin):
-    """
-    Plugin to interact with a `BME280 <https://shop.pimoroni.com/products/bme280-breakout>`_ environment sensor for
-    temperature, humidity and pressure measurements over I2C interface
-
-    Requires:
-
-        * ``pimoroni-bme280`` (``pip install pimoroni-bme280``)
-    """
-
-    def __init__(self, port=1, **kwargs):
-        """
-        :param port: I2C port. 0 = /dev/i2c-0 (port I2C0), 1 = /dev/i2c-1 (port I2C1)
-        """
-
-        super().__init__(**kwargs)
-        self.port = port
-        self._bus = None
-        self._device = None
-
-    # noinspection PyPackageRequirements
-    # noinspection PyUnresolvedReferences
-    def _get_device(self):
-        if self._device:
-            return self._device
-
-        from smbus import SMBus
-        from bme280 import BME280
-
-        self._bus = SMBus(self.port)
-        self._device = BME280(i2c_dev=self._bus)
-        return self._device
-
-    @action
-    def get_measurement(self):
-        """
-        :returns: dict. Example:
-
-        .. code-block:: python
-
-           output = {
-               "temperature": 21.0,   # Celsius
-               "pressure": 101555.08, # Pascals
-               "humidity": 23.543,    # percentage
-               "altitude": 15.703     # meters
-           }
-
-        """
-
-        device = self._get_device()
-        return {
-            'temperature': device.get_temperature(),
-            'pressure': device.get_pressure()*100,
-            'humidity': device.get_humidity(),
-            'altitude': device.get_altitude(),
-        }
-
-
-# vim:sw=4:ts=4:et:

platypush/plugins/gpio/sensor/bme280/manifest.yaml

@@ -1,7 +0,0 @@
-manifest:
-  events: {}
-  install:
-    pip:
-    - pimoroni-bme280
-  package: platypush.plugins.gpio.sensor.bme280
-  type: plugin

platypush/plugins/sensor/__init__.py

@@ -1,26 +1,350 @@
 from abc import ABC, abstractmethod
+from types import NoneType
+from typing import Collection, Iterable, List, Mapping, Optional, Tuple, Type, Union
+from typing_extensions import override
 
-from platypush.plugins import Plugin, action
+from platypush.common.sensors import Numeric, SensorDataType
+from platypush.context import get_bus
+from platypush.entities import Entity
+from platypush.entities.managers.sensors import SensorEntityManager
+from platypush.message.event.sensor import (
+    SensorDataAboveThresholdEvent,
+    SensorDataBelowThresholdEvent,
+    SensorDataChangeEvent,
+    SensorDataEvent,
+)
+from platypush.plugins import RunnablePlugin, action
+from platypush.utils import get_plugin_name_by_class
+
+ThresholdType = Union[Numeric, Tuple[Numeric, Numeric]]
+ThresholdConfiguration = Union[ThresholdType, Mapping[str, ThresholdType]]
 
 
-class SensorPlugin(Plugin, ABC):
+class SensorPlugin(RunnablePlugin, SensorEntityManager, ABC):
     """
     Sensor abstract plugin. Any plugin that interacts with sensors
-    should implement this class (and the get_measurement() method)
+    should implement this class.
+
+    Triggers:
+
+        * :class:`platypush.message.event.sensor.SensorDataAboveThresholdEvent`
+        * :class:`platypush.message.event.sensor.SensorDataBelowThresholdEvent`
+        * :class:`platypush.message.event.sensor.SensorDataChangeEvent`
+
     """
 
-    def __init__(self, **kwargs):
+    _max_retry_secs = 60.0
+    """
+    In case of failure, we apply an exponential back-off retry algorithm. This
+    is the maximum number of seconds that we should wait during these retries.
+    """
+
+    def __init__(
+        self,
+        thresholds: Optional[ThresholdConfiguration] = None,
+        tolerance: SensorDataType = 0,
+        enabled_sensors: Optional[Iterable[str]] = None,
+        **kwargs,
+    ):
+        """
+        :param thresholds: A number, numeric pair or mapping of ``str`` to
+            number/numeric pair representing the thresholds for the sensor.
+
+            Examples:
+
+                .. code-block:: yaml
+
+                    # Any value below 25 from any sensor will trigger a
+                    # SensorDataBelowThresholdEvent, if the previous value was
+                    # equal or above, and any value above 25 will trigger a
+                    # SensorDataAboveThresholdEvent, if the previous value was
+                    # equal or below
+                    thresholds: 25.0
+
+                    # Same as above, but the threshold is only applied to
+                    # ``temperature`` readings
+                    thresholds:
+                        temperature: 25.0
+
+                    # Any value below 20 from any sensor will trigger a
+                    # SensorDataBelowThresholdEvent, if the previous value was
+                    # equal or above, and any value above 25 will trigger a
+                    # SensorDataAboveThresholdEvent, if the previous value was
+                    # equal or below (hysteresis configuration with double
+                    # threshold)
+                    thresholds:
+                        - 20.0
+                        - 25.0
+
+                    # Same as above, but the threshold is only applied to
+                    # ``temperature`` readings
+                    thresholds:
+                        temperature:
+                            - 20.0
+                            - 25.0
+
+        :param tolerance: If set, then the sensor change events will be
+            triggered only if the difference between the new value and the
+            previous value is higher than the specified tolerance. For example,
+            if the sensor data is mapped to a dictionary::
+
+                {
+                    "temperature": 0.01,  # Tolerance on the 2nd decimal digit
+                    "humidity": 0.1       # Tolerance on the 1st decimal digit
+                }
+
+            Or, if it's a raw scalar number::
+
+                0.1  # Tolerance on the 1st decimal digit
+
+            Or, if it's a list of values::
+
+                [
+                    0.01,   # Tolerance on the 2nd decimal digit for the first value
+                    0.1     # Tolerance on the 1st decimal digit for the second value
+                ]
+
+        :param enabled_sensors: If :meth:`.get_measurement` returns a key-value
+            mapping, and ``enabled_sensors`` is set, then only the reported
+            sensor keys will be returned.
+        """
         super().__init__(**kwargs)
+        self._tolerance = tolerance
+        self._thresholds = thresholds
+        self._enabled_sensors = set(enabled_sensors or [])
+        self._last_measurement: Optional[SensorDataType] = None
+        """ Latest measurement from the sensor. """
+
+    def _has_changes_scalar(
+        self,
+        old_data: Union[int, float],
+        new_data: Union[int, float],
+        attr: Optional[str] = None,
+        index: Optional[int] = None,
+    ) -> bool:
+        """
+        Returns ``True`` if the new data has changes compared to the old data -
+        limited to numeric scalar values.
+        """
+        if isinstance(self._tolerance, (int, float)):
+            tolerance = self._tolerance
+        elif isinstance(self._tolerance, dict) and attr:
+            tolerance = self._tolerance.get(attr, 0)  # type: ignore
+        elif isinstance(self._tolerance, (list, tuple)) and index:
+            tolerance = self._tolerance[index]
+        else:
+            tolerance = 0
+
+        return abs(old_data - new_data) > tolerance
+
+    def _has_changes(
+        self,
+        old_data: Optional[SensorDataType],
+        new_data: Optional[SensorDataType],
+        attr: Optional[str] = None,
+        index: Optional[int] = None,
+    ) -> bool:
+        """
+        Returns ``True`` if the new data has changes compared to the old data.
+        It also applies the configured tolerance thresholds.
+        """
+        # If there is no previous data, then the new data will always be a change
+        if old_data is None:
+            return True
+
+        # If the new data is missing, then we have no new changes
+        if new_data is None:
+            return False
+
+        # If the data is scalar, then run the comparison logic
+        if isinstance(old_data, (int, float)) and isinstance(new_data, (int, float)):
+            return self._has_changes_scalar(old_data, new_data, attr, index)
+
+        # If the data is dict-like, recursively call _has_changes on its attributes
+        if isinstance(old_data, dict) and isinstance(new_data, dict):
+            return any(
+                self._has_changes(old_data.get(attr), value, attr=attr)  # type: ignore
+                for attr, value in new_data.items()
+            )
+
+        # If the data is list-like, recursively call _has_changes on its values
+        if isinstance(old_data, (list, tuple)) and isinstance(new_data, (list, tuple)):
+            return any(
+                self._has_changes(old_data[i], value, index=i)
+                for i, value in enumerate(new_data)
+            )
+
+        raise AssertionError(
+            f'Mismatching types for old_data and new_data: "{type(old_data)}" '
+            f'and "{type(new_data)}"'
+        )
+
+    def _process_scalar_threshold_events(
+        self,
+        old_data: Optional[Numeric],
+        new_data: Numeric,
+        attr: Optional[str] = None,
+    ) -> List[SensorDataEvent]:
+        """
+        Inner scalar processing for sensor above/below threshold events.
+        """
+        event_types: List[Type[SensorDataEvent]] = []
+        event_args = {
+            'source': get_plugin_name_by_class(self.__class__),
+        }
+
+        # If we're mapping against a dict attribute, extract its thresholds,
+        # otherwise use the default configured thresholds
+        thresholds = (
+            self._thresholds.get(attr)
+            if attr and isinstance(self._thresholds, dict)
+            else self._thresholds
+        )
+
+        # Normalize low/high thresholds
+        low_t, high_t = (
+            sorted(thresholds[:2])
+            if isinstance(thresholds, (list, tuple))
+            else (thresholds, thresholds)
+        )
+
+        if low_t is None or high_t is None:
+            return []
+
+        assert isinstance(low_t, Numeric) and isinstance(
+            high_t, Numeric
+        ), f'Non-numeric thresholds detected: "{low_t}" and "{high_t}"'
+
+        # Above threshold case
+        if (old_data is None or old_data <= high_t) and new_data > high_t:
+            event_types.append(SensorDataAboveThresholdEvent)
+        # Below threshold case
+        elif (old_data is None or old_data >= low_t) and new_data < low_t:
+            event_types.append(SensorDataBelowThresholdEvent)
+
+        return [
+            event_type(
+                data={attr: new_data} if attr else new_data,
+                **event_args,
+            )
+            for event_type in event_types
+        ]
+
+    def _process_threshold_events(
+        self,
+        old_data: Optional[SensorDataType],
+        new_data: SensorDataType,
+        attr: Optional[str] = None,
+    ) -> List[SensorDataEvent]:
+        """
+        Processes sensor above/below threshold events.
+        """
+        events: List[SensorDataEvent] = []
+
+        # If there are no configured thresholds, there's nothing to do
+        if self._thresholds in (None, {}, (), []):
+            return events
+
+        # Scalar case
+        if isinstance(old_data, (Numeric, NoneType)) and isinstance(new_data, Numeric):
+            return self._process_scalar_threshold_events(
+                old_data, new_data, attr  # type: ignore
+            )
+
+        # From here on, threshold comparison only applies if both the old and
+        # new data is a str -> number mapping
+        if not (isinstance(old_data, (dict, NoneType)) and isinstance(new_data, dict)):
+            return events
+
+        # Recursively call _process_threshold_events on the data attributes
+        for attr, value in new_data.items():  # type: ignore
+            events.extend(
+                self._process_threshold_events(
+                    old_data=(
+                        old_data.get(attr)  # type: ignore
+                        if isinstance(old_data, dict)
+                        else old_data
+                    ),
+                    new_data=value,
+                    attr=str(attr),
+                )
+            )
+
+        return events
+
+    def _process_sensor_events(
+        self, old_data: Optional[SensorDataType], new_data: Optional[SensorDataType]
+    ):
+        """
+        Given the previous and new measurement, it runs the comparison logic
+        against the configured tolerance values and thresholds, and it
+        processes the required sensor data change and above/below threshold
+        events.
+        """
+        # If the new data is missing or there are no changes, there are no
+        # events to process
+        if new_data is None or not self._has_changes(old_data, new_data):
+            return
+
+        events = [
+            SensorDataChangeEvent(
+                data=new_data,  # type: ignore
+                source=get_plugin_name_by_class(self.__class__),
+            ),
+            *self._process_threshold_events(old_data, new_data),
+        ]
+
+        for event in events:
+            get_bus().post(event)
+
+        self.publish_entities(new_data)
+
+    def _update_last_measurement(self, new_data: SensorDataType):
+        """
+        Update the ``_last_measurement`` attribute with the newly acquired data.
+        """
+        # If there is no last measurement, or either the new or old
+        # measurements are not dictionaries, then overwrite the previous data
+        # with the new data
+        if not (
+            isinstance(self._last_measurement, dict) and isinstance(new_data, dict)
+        ):
+            self._last_measurement = new_data
+
+        # Otherwise, merge the old data with the new
+        self._last_measurement.update(new_data)  # type: ignore
+
+    def _filter_enabled_sensors(self, data: SensorDataType) -> SensorDataType:
+        """
+        If ``data`` is a sensor mapping, and ``enabled_sensors`` is set, filter
+        out only the requested keys.
+        """
+        if not (isinstance(data, dict) and self._enabled_sensors):
+            return data
+
+        return {k: v for k, v in data.items() if k in self._enabled_sensors}
+
+    @override
+    @abstractmethod
+    def transform_entities(self, entities: SensorDataType) -> Collection[Entity]:
+        raise NotImplementedError()
+
+    @override
+    def publish_entities(
+        self, entities: SensorDataType, *args, **kwargs
+    ) -> Collection[Entity]:
+        entities_args = [entities] if isinstance(entities, Numeric) else entities
+        return super().publish_entities(entities_args, *args, **kwargs)  # type: ignore
 
     @abstractmethod
     @action
-    def get_measurement(self, *args, **kwargs):
+    def get_measurement(self, *args, **kwargs) -> SensorDataType:
         """
         Implemented by the subclasses.
 
-        :returns: Either a raw scalar:
+        :returns: Either a raw scalar::
 
-            ``output = 273.16``
+            output = 273.16
 
         or a name-value dictionary with the values that have been read::
 
@@ -31,7 +355,7 @@ class SensorPlugin(Plugin, ABC):
 
         or a list of values::
 
-            [
+            output = [
                 0.01,
                 0.34,
                 0.53,
@@ -39,18 +363,52 @@ class SensorPlugin(Plugin, ABC):
             ]
 
         """
-        raise NotImplementedError('get_measurement should be implemented in a derived class')
+        raise NotImplementedError()
 
     @action
     def get_data(self, *args, **kwargs):
         """
-        Alias for ``get_measurement``
+        (Deprecated) alias for :meth:`.get_measurement``
         """
-        return self.get_measurement(*args, **kwargs).output
+        return self.get_measurement(*args, **kwargs)
 
     @action
-    def close(self):
+    def status(self, *_, **__) -> Optional[SensorDataType]:
-        pass
+        """
+        Returns the latest read values and publishes the
+        :class:`platypush.message.event.entities.EntityUpdateEvent` events if
+        required.
+        """
+        if self._last_measurement is not None:
+            self.publish_entities(self._last_measurement)
+        return self._last_measurement
+
+    @override
+    def main(self):
+        sleep_retry_secs = 1  # Exponential back-off
+
+        while not self.should_stop():
+            try:
+                new_data: SensorDataType = self.get_measurement().output  # type: ignore
+                # Reset the exponential back-off retry counter in case of success
+                sleep_retry_secs = 1
+            except Exception as e:
+                self.logger.warning(
+                    'Could not update the status: %s. Next retry in %d seconds',
+                    e,
+                    sleep_retry_secs,
+                )
+                self.wait_stop(sleep_retry_secs)
+                sleep_retry_secs = min(
+                    sleep_retry_secs * 2,
+                    self._max_retry_secs,
+                )
+                continue
+
+            new_data = self._filter_enabled_sensors(new_data)
+            self._process_sensor_events(self._last_measurement, new_data)
+            self._update_last_measurement(new_data)
+            self.wait_stop(self.poll_interval)
 
 
 # vim:sw=4:ts=4:et:

platypush/plugins/sensor/bme280/__init__.py

@@ -0,0 +1,155 @@
+from dataclasses import dataclass
+from typing import Dict, List, Type
+from typing_extensions import override
+
+from platypush.common.sensors import Numeric
+from platypush.entities.devices import Device
+from platypush.entities.distance import DistanceSensor
+from platypush.entities.humidity import HumiditySensor
+from platypush.entities.pressure import PressureSensor
+from platypush.entities.sensors import NumericSensor
+from platypush.entities.temperature import TemperatureSensor
+from platypush.plugins import action
+from platypush.plugins.sensor import SensorPlugin
+
+
+@dataclass
+class SensorEntityMapping:
+    """
+    Maps the dict-like data returned by the plugin to corresponding sensor
+    entities.
+    """
+
+    name: str
+    unit: str
+    entity_type: Type[NumericSensor]
+
+    @property
+    def id(self):
+        """
+        The standardized external ID for the entity.
+        """
+        return f'bme280:{self.name}'
+
+
+_sensor_entity_mappings = {
+    mapping.name: mapping
+    for mapping in [
+        SensorEntityMapping(
+            name='temperature',
+            unit='°C',
+            entity_type=TemperatureSensor,
+        ),
+        SensorEntityMapping(
+            name='humidity',
+            unit='%',
+            entity_type=HumiditySensor,
+        ),
+        SensorEntityMapping(
+            name='pressure',
+            unit='Pa',
+            entity_type=PressureSensor,
+        ),
+        SensorEntityMapping(
+            name='altitude',
+            unit='m',
+            entity_type=DistanceSensor,
+        ),
+    ]
+}
+
+
+# pylint: disable=too-many-ancestors
+class SensorBme280Plugin(SensorPlugin):
+    """
+    Plugin to interact with a `BME280 <https://shop.pimoroni.com/products/bme280-breakout>`_ environment sensor for
+    temperature, humidity and pressure measurements over I2C interface
+
+    Requires:
+
+        * ``pimoroni-bme280`` (``pip install pimoroni-bme280``)
+
+    Triggers:
+
+        * :class:`platypush.message.event.sensor.SensorDataAboveThresholdEvent`
+        * :class:`platypush.message.event.sensor.SensorDataBelowThresholdEvent`
+        * :class:`platypush.message.event.sensor.SensorDataChangeEvent`
+
+    """
+
+    def __init__(self, port: int = 1, **kwargs):
+        """
+        :param port: I2C port. 0 = /dev/i2c-0 (port I2C0), 1 = /dev/i2c-1 (port I2C1)
+        """
+
+        super().__init__(**kwargs)
+        self.port = port
+        self._bus = None
+        self._device = None
+
+    def _get_device(self):
+        from smbus import SMBus
+        from bme280 import BME280
+
+        if self._device:
+            return self._device
+
+        self._bus = SMBus(self.port)
+        self._device = BME280(i2c_dev=self._bus)
+        return self._device
+
+    @override
+    @action
+    def get_measurement(self, *_, **__):
+        """
+        :returns: dict. Example:
+
+        .. code-block:: python
+
+           output = {
+               "temperature": 21.0,   # Celsius
+               "pressure": 101555.08, # Pascals
+               "humidity": 23.543,    # percentage
+               "altitude": 15.703     # meters
+           }
+
+        """
+
+        device = self._get_device()
+        return {
+            'temperature': device.get_temperature(),
+            'pressure': device.get_pressure() * 100,
+            'humidity': device.get_humidity(),
+            'altitude': device.get_altitude(),
+        }
+
+    @override
+    def transform_entities(self, entities: Dict[str, Numeric]) -> List[Device]:
+        sensors = []
+        for sensor, value in entities.items():
+            if value is None:
+                continue
+
+            mapping = _sensor_entity_mappings[sensor]
+            sensors.append(
+                mapping.entity_type(
+                    id=mapping.id,
+                    name=mapping.name,
+                    value=value,
+                    unit=mapping.unit,
+                )
+            )
+
+        if not sensors:
+            return []
+
+        return [
+            Device(
+                id='bme280',
+                name='BME280 Sensor',
+                children=sensors,
+            )
+        ]
+
+
+# vim:sw=4:ts=4:et:

platypush/plugins/sensor/bme280/manifest.yaml

@@ -0,0 +1,10 @@
+manifest:
+  events:
+    platypush.message.event.sensor.SensorDataAboveThresholdEvent:
+    platypush.message.event.sensor.SensorDataBelowThresholdEvent:
+    platypush.message.event.sensor.SensorDataChangeEvent:
+  install:
+    pip:
+    - pimoroni-bme280
+  package: platypush.plugins.sensor.bme280
+  type: plugin

platypush/plugins/sensor/distance/vl53l1x/__init__.py

@@ -3,16 +3,13 @@ from threading import RLock
 from typing import List, Mapping
 from typing_extensions import override
 
-from platypush.context import get_bus
-from platypush.entities.managers.sensors import SensorEntityManager
 from platypush.entities.devices import Device
 from platypush.entities.distance import DistanceSensor
-from platypush.message.event.sensor import SensorDataChangeEvent
+from platypush.plugins.sensor import SensorPlugin
-from platypush.plugins import RunnablePlugin, action
-from platypush.utils import get_plugin_name_by_class
 
 
-class SensorDistanceVl53l1xPlugin(RunnablePlugin, SensorEntityManager):
+# pylint: disable=too-many-ancestors
+class SensorDistanceVl53l1xPlugin(SensorPlugin):
     """
     Plugin to interact with an `VL53L1x
     <https://www.st.com/en/imaging-and-photonics-solutions/vl53l1x.html>`_
@@ -68,13 +65,8 @@ class SensorDistanceVl53l1xPlugin(RunnablePlugin, SensorEntityManager):
                 self._device.close()
                 self._device = None
 
-    @action
     @override
-    def status(self, *_, **__):
+    def get_measurement(self, *_, short=True, medium=True, long=True, **__):
-        self.publish_entities(self._last_data)
-        return self._last_data
-
-    def _status(self, *_, short=True, medium=True, long=True, **__):
         """
         :param short: Enable short range measurement (default: True)
         :param medium: Enable medium range measurement (default: True)
@@ -117,20 +109,6 @@ class SensorDistanceVl53l1xPlugin(RunnablePlugin, SensorEntityManager):
 
         return ret
 
-    @action
-    def get_data(self, *args, **kwargs):
-        """
-        (Deprecated) alias for :meth:`.status`.
-        """
-        return self.status(*args, **kwargs)
-
-    @action
-    def get_measurement(self, *args, **kwargs):
-        """
-        (Deprecated) alias for :meth:`.status`.
-        """
-        return self.status(*args, **kwargs)
-
     @override
     def transform_entities(self, entities: Mapping[str, int]) -> List[Device]:
         return super().transform_entities(  # type: ignore
@@ -151,25 +129,5 @@ class SensorDistanceVl53l1xPlugin(RunnablePlugin, SensorEntityManager):
             ]
         )
 
-    @override
-    def publish_entities(self, entities: Mapping[str, int], *_, **__) -> List[Device]:
-        get_bus().post(
-            SensorDataChangeEvent(
-                data=entities,
-                source=get_plugin_name_by_class(self.__class__),
-            )
-        )
-        return super().publish_entities(entities)  # type: ignore
-
-    @override
-    def main(self):
-        while not self.should_stop():
-            status = self._status()
-            if status != self._last_data:
-                self.publish_entities(status)
-
-            self._last_data = status
-            self.wait_stop(self.poll_interval)
-
 
 # vim:sw=4:ts=4:et:

platypush/plugins/serial/__init__.py

@@ -1,47 +1,142 @@
 import base64
+from collections import namedtuple
 import json
-import serial
+from typing import Dict, List, Optional, Union
 import threading
-import time
+from typing_extensions import override
 
+from serial import Serial
+
+from platypush.common.sensors import Numeric
+from platypush.entities.devices import Device
+from platypush.entities.sensors import RawSensor, NumericSensor
 from platypush.plugins import action
 from platypush.plugins.sensor import SensorPlugin
+from platypush.utils import get_lock
+
+_DeviceAndRate = namedtuple('_DeviceAndRate', ['device', 'baud_rate'])
 
 
 class SerialPlugin(SensorPlugin):
     """
-    The serial plugin can read data from a serial device, as long as the serial
+    The serial plugin can read data from a serial device.
-    device returns a JSON. You can use this plugin to interact for example with
+
-    some sensors connected through an Arduino. Just make sure that the code on
+    If the device returns a JSON string, then that string will be parsed for
-    your serial device returns JSON values. If you're using an Arduino or any
+    individual values. For example:
-    ATMega compatible device, take a look at
+
-    https://github.com/bblanchon/ArduinoJson.
+        .. code-block:: json
+
+            {"temperature": 25.0, "humidity": 15.0}
+
+    If the serial device returns such a value, then ``temperature`` and
+    ``humidity`` will be parsed as separate entities with the same names as the
+    keys provided on the payload.
+
+    The JSON option is a good choice if you have an Arduino/ESP-like device
+    whose code you can control, as it allows to easily send data to Platypush
+    in a simple key-value format. The use-case would be that of an Arduino/ESP
+    device that pushes data on the wire, and this integration would then listen
+    for updates.
+
+    Alternatively, you can also use this integration in a more traditional way
+    through the :meth:`.read` and :meth:`.write` methods to read and write data
+    to the device. In such a case, you may want to disable the "smart polling"
+    by setting ``enable_polling`` to ``False`` in the configuration.
+
+    If you want an out-of-the-box solution with a Firmata-compatible firmware,
+    you may consider using the :class:`platypush.plugin.arduino.ArduinoPlugin`
+    instead.
+
+    Note that device paths on Linux may be subject to change. If you want to
+    create static naming associations for your devices (e.g. make sure that
+    your Arduino will always be symlinked to ``/dev/arduino`` instead of
+    ``/dev/ttyUSB<n>``), you may consider creating `static mappings through
+    udev
+    <https://dev.to/enbis/how-udev-rules-can-help-us-to-recognize-a-usb-to-serial-device-over-dev-tty-interface-pbk>`_.
+
+    Requires:
+
+        * **pyserial** (``pip install pyserial``)
+
+    Triggers:
+
+        * :class:`platypush.message.event.sensor.SensorDataAboveThresholdEvent`
+        * :class:`platypush.message.event.sensor.SensorDataBelowThresholdEvent`
+        * :class:`platypush.message.event.sensor.SensorDataChangeEvent`
+
     """
 
-    def __init__(self, device=None, baud_rate=9600, **kwargs):
+    _default_lock_timeout: float = 2.0
+
+    def __init__(
+        self,
+        device: Optional[str] = None,
+        baud_rate: int = 9600,
+        max_size: int = 1 << 19,
+        timeout: float = _default_lock_timeout,
+        enable_polling: bool = True,
+        poll_interval: float = 0.1,
+        **kwargs,
+    ):
         """
         :param device: Device path (e.g. ``/dev/ttyUSB0`` or ``/dev/ttyACM0``)
-        :type device: str
-
         :param baud_rate: Serial baud rate (default: 9600)
-        :type baud_rate: int
+        :param max_size: Maximum size of a JSON payload (default: 512 KB). The
+            plugin will keep reading bytes from the wire until it can form a
+            valid JSON payload, so this upper limit is required to prevent the
+            integration from listening forever and dumping garbage in memory.
+        :param timeout: This integration will ensure that only one
+            reader/writer can access the serial device at the time, in order to
+            prevent mixing up bytes in the response. This value specifies how
+            long we should wait for a pending action to terminate when we try
+            to run a new action. Default: 2 seconds.
+        :param enable_polling: If ``False``, the plugin will not poll the
+            device for updates. This can be the case if you want to
+            programmatically interface with the device via the :meth:`.read`
+            and :meth:`.write` methods instead of polling for updates in JSON
+            format.
+        :param poll_interval: How often (in seconds) we should poll the device
+            for new data. Since we are reading JSON data from a serial
+            interface whenever it's ready, the default here can be quite low
+            (default: 0.1 seconds).
         """
-
+        super().__init__(poll_interval=poll_interval, **kwargs)
-        super().__init__(**kwargs)
 
         self.device = device
         self.baud_rate = baud_rate
         self.serial = None
-        self.serial_lock = threading.Lock()
+        self.serial_lock = threading.RLock()
-        self.last_measurement = None
+        self.last_data: dict = {}
+        self._max_size = max_size
+        self._timeout = timeout
+        self._enable_polling = enable_polling
 
-    def _read_json(self, serial_port):
+    def _read_json(
+        self,
+        serial_port: Serial,
+        max_size: Optional[int] = None,
+    ) -> str:
+        """
+        Reads a JSON payload from the wire. It counts the number of curly
+        brackets detected, ignoring everything before the first curly bracket,
+        and it stops when the processed payload has balanced curly brackets -
+        i.e. it can be mapped to JSON.
+
+        :param serial_port: Serial connection.
+        :param max_size: Default ``max_size`` override.
+        """
         n_brackets = 0
         is_escaped_ch = False
         parse_start = False
         output = bytes()
+        max_size = max_size or self._max_size
 
         while True:
+            assert len(output) <= max_size, (
+                'Maximum allowed size exceeded while reading from the device: '
+                f'read {len(output)} bytes'
+            )
+
             ch = serial_port.read()
             if not ch:
                 break
@@ -70,15 +165,27 @@ class SerialPlugin(SensorPlugin):
 
         return output.decode().strip()
 
-    def _get_serial(self, device=None, baud_rate=None, reset=False):
+    def __get_serial(
+        self,
+        device: Optional[str] = None,
+        baud_rate: Optional[int] = None,
+        reset: bool = False,
+    ) -> Serial:
+        """
+        Return a ``Serial`` connection object to the given device.
+
+        :param device: Default device path override.
+        :param baud_rate: Default baud rate override.
+        :param reset: By default, if a connection to the device is already open
+            then the current object will be returned. If ``reset=True``, the
+            connection will be reset and a new one will be created instead.
+        """
         if not device:
-            if not self.device:
+            assert self.device, 'No device specified nor default device configured'
-                raise RuntimeError('No device specified nor default device configured')
             device = self.device
 
         if baud_rate is None:
-            if self.baud_rate is None:
+            assert self.baud_rate, 'No baud_rate specified nor default configured'
-                raise RuntimeError('No baud_rate specified nor default configured')
             baud_rate = self.baud_rate
 
         if self.serial:
@@ -87,192 +194,240 @@ class SerialPlugin(SensorPlugin):
 
             self._close_serial()
 
-        self.serial = serial.Serial(device, baud_rate)
+        self.serial = Serial(device, baud_rate)
         return self.serial
 
+    def _get_serial(
+        self,
+        device: Optional[str] = None,
+        baud_rate: Optional[int] = None,
+    ) -> Serial:
+        """
+        Return a ``Serial`` connection object to the given device.
+
+        :param device: Default device path override.
+        :param baud_rate: Default baud rate override.
+        :param reset: By default, if a connection to the device is already open
+            then the current object will be returned. If ``reset=True``, the
+            connection will be reset and a new one will be created instead.
+        """
+        try:
+            return self.__get_serial(device, baud_rate)
+        except AssertionError as e:
+            raise e
+        except Exception as e:
+            self.logger.debug(e)
+            self.wait_stop(1)
+            return self.__get_serial(device=device, baud_rate=baud_rate, reset=True)
+
     def _close_serial(self):
+        """
+        Close the serial connection if it's currently open.
+        """
         if self.serial:
             try:
                 self.serial.close()
-                self.serial = None
             except Exception as e:
-                self.logger.warning('Error while closing serial communication: {}')
+                self.logger.warning('Error while closing serial communication: %s', e)
                 self.logger.exception(e)
 
-    @action
+            self.serial = None
-    def get_measurement(self, device=None, baud_rate=None):
+
+    def _get_device_and_baud_rate(
+        self, device: Optional[str] = None, baud_rate: Optional[int] = None
+    ) -> _DeviceAndRate:
         """
-        Reads JSON data from the serial device and returns it as a message
+        Gets the device path and baud rate from the given device and baud rate
+        if set, or it falls back on the default configured ones.
 
-        :param device: Device path (default: default configured device)
+        :raise AssertionError: If neither ``device`` nor ``baud_rate`` is set
-        :type device: str
+            nor configured.
-
-        :param baud_rate: Baud rate (default: default configured baud_rate)
-        :type baud_rate: int
         """
 
         if not device:
-            if not self.device:
+            assert (
-                raise RuntimeError('No device specified nor default device configured')
+                self.device
+            ), 'No device specified and a default one is not configured'
             device = self.device
 
         if baud_rate is None:
-            if self.baud_rate is None:
+            assert (
-                raise RuntimeError('No baud_rate specified nor default configured')
+                self.baud_rate is not None
+            ), 'No baud_rate specified nor a default value is configured'
             baud_rate = self.baud_rate
 
+        return _DeviceAndRate(device, baud_rate)
+
+    @override
+    @action
+    def get_measurement(
+        self,
+        *_,
+        device: Optional[str] = None,
+        baud_rate: Optional[int] = None,
+        **__,
+    ) -> Dict[str, Numeric]:
+        """
+        Reads JSON data from the serial device and returns it as a message
+
+        :param device: Device path (default: default configured device).
+        :param baud_rate: Baud rate (default: default configured baud_rate).
+        """
+
+        device, baud_rate = self._get_device_and_baud_rate(device, baud_rate)
         data = None
 
-        try:
+        with get_lock(self.serial_lock, timeout=self._timeout) as serial_available:
-            serial_available = self.serial_lock.acquire(timeout=2)
             if serial_available:
-                try:
                 ser = self._get_serial(device=device, baud_rate=baud_rate)
-                except Exception as e:
-                    self.logger.debug(e)
-                    time.sleep(1)
-                    ser = self._get_serial(device=device, baud_rate=baud_rate, reset=True)
-
                 data = self._read_json(ser)
 
                 try:
-                    data = json.loads(data)
+                    data = dict(json.loads(data))
-                except (ValueError, TypeError):
+                except (ValueError, TypeError) as e:
-                    self.logger.warning('Invalid JSON message from {}: {}'.format(self.device, data))
+                    raise AssertionError(
+                        f'Invalid JSON message from {device}: {e}. Message: {data}'
+                    ) from e
             else:
-                data = self.last_measurement
+                data = self.last_data
-        finally:
-            try:
-                self.serial_lock.release()
-            except Exception as e:
-                self.logger.debug(e)
 
         if data:
-            self.last_measurement = data
+            self.last_data = data
 
         return data
 
     @action
-    def read(self, device=None, baud_rate=None, size=None, end=None):
+    def read(
+        self,
+        device: Optional[str] = None,
+        baud_rate: Optional[int] = None,
+        size: Optional[int] = None,
+        end: Optional[Union[int, str]] = None,
+        binary: bool = False,
+    ) -> str:
         """
         Reads raw data from the serial device
 
         :param device: Device to read (default: default configured device)
-        :type device: str
-
         :param baud_rate: Baud rate (default: default configured baud_rate)
-        :type baud_rate: int
-
         :param size: Number of bytes to read
-        :type size: int
+        :param end: End of message, as a character or bytecode
-
+        :param binary: If set to ``True``, then the serial output will be
-        :param end: End of message byte or character
+            interpreted as binary data and a base64-encoded representation will
-        :type end: int, bytes or str
+            be returned. Otherwise, the output will be interpreted as a UTF-8
+            encoded string.
+        :return: The read message as a UTF-8 string if ``binary=False``,
+            otherwise as a base64-encoded string.
         """
 
-        if not device:
+        device, baud_rate = self._get_device_and_baud_rate(device, baud_rate)
-            if not self.device:
+        assert not (
-                raise RuntimeError('No device specified nor default device configured')
+            (size is None and end is None) or (size is not None and end is not None)
-            device = self.device
+        ), 'Either size or end must be specified'
 
-        if baud_rate is None:
+        assert not (
-            if self.baud_rate is None:
+            end and isinstance(end, str) and len(end) > 1
-                raise RuntimeError('No baud_rate specified nor default configured')
+        ), 'The serial end must be a single character, not a string'
-            baud_rate = self.baud_rate
-
-        if (size is None and end is None) or (size is not None and end is not None):
-            raise RuntimeError('Either size or end must be specified')
-
-        if end and isinstance(end, str) and len(end) > 1:
-            raise RuntimeError('The serial end must be a single character, not a string')
 
         data = bytes()
 
-        try:
+        with get_lock(self.serial_lock, timeout=self._timeout) as serial_available:
-            serial_available = self.serial_lock.acquire(timeout=2)
+            assert serial_available, 'Serial read timed out'
-            if serial_available:
-                try:
-                    ser = self._get_serial(device=device, baud_rate=baud_rate)
-                except Exception as e:
-                    self.logger.debug(e)
-                    time.sleep(1)
-                    ser = self._get_serial(device=device, baud_rate=baud_rate, reset=True)
 
+            ser = self._get_serial(device=device, baud_rate=baud_rate)
             if size is not None:
                 for _ in range(0, size):
                     data += ser.read()
             elif end is not None:
-                    if isinstance(end, str):
+                end_byte = end.encode() if isinstance(end, str) else bytes([end])
-                        end = end.encode()
-
                 ch = None
-                    while ch != end:
-                        ch = ser.read()
 
+                while ch != end_byte:
+                    ch = ser.read()
                     if ch != end:
                         data += ch
-            else:
-                self.logger.warning('Serial read timeout')
-        finally:
-            try:
-                self.serial_lock.release()
-            except Exception as e:
-                self.logger.debug(e)
 
-        try:
+        return base64.b64encode(data).decode() if binary else data.decode('utf-8')
-            data = data.decode()
-        except (ValueError, TypeError):
-            data = base64.encodebytes(data)
-
-        return data
 
     @action
-    def write(self, data, device=None, baud_rate=None):
+    def write(
+        self,
+        data: Union[str, dict, list, bytes, bytearray],
+        device: Optional[str] = None,
+        baud_rate: Optional[int] = None,
+        binary: bool = False,
+    ):
         """
         Writes data to the serial device.
 
-        :param device: Device to write (default: default configured device)
+        :param device: Device to write (default: default configured device).
-        :type device: str
+        :param baud_rate: Baud rate (default: default configured baud_rate).
+        :param data: Data to send to the serial device. It can be any of the following:
 
-        :param baud_rate: Baud rate (default: default configured baud_rate)
+            - A UTF-8 string
-        :type baud_rate: int
+            - A base64-encoded string (if ``binary=True``)
+            - A dictionary/list that will be encoded as JSON
+            - A bytes/bytearray sequence
 
-        :param data: Data to send to the serial device
+        :param binary: If ``True``, then the message is either a
-        :type data: str, bytes or dict. If dict, it will be serialized as JSON.
+            bytes/bytearray sequence or a base64-encoded string.
         """
 
-        if not device:
+        device, baud_rate = self._get_device_and_baud_rate(device, baud_rate)
-            if not self.device:
+        if isinstance(data, (dict, list)):
-                raise RuntimeError('No device specified nor default device configured')
-            device = self.device
-
-        if baud_rate is None:
-            if self.baud_rate is None:
-                raise RuntimeError('No baud_rate specified nor default configured')
-            baud_rate = self.baud_rate
-
-        if isinstance(data, dict):
             data = json.dumps(data)
         if isinstance(data, str):
-            data = data.encode('utf-8')
+            data = base64.b64decode(data) if binary else data.encode('utf-8')
 
-        try:
+        data = bytes(data)
-            serial_available = self.serial_lock.acquire(timeout=2)
+        with get_lock(self.serial_lock, timeout=self._timeout) as serial_available:
-            if serial_available:
+            assert serial_available, 'Could not acquire the device lock'
-                try:
             ser = self._get_serial(device=device, baud_rate=baud_rate)
-                except Exception as e:
+            self.logger.info('Writing %d bytes to %s', len(data), device)
-                    self.logger.debug(e)
-                    time.sleep(1)
-                    ser = self._get_serial(device=device, baud_rate=baud_rate, reset=True)
-
-                self.logger.info('Writing {} to {}'.format(data, self.device))
             ser.write(data)
-        finally:
+
+    @override
+    def transform_entities(self, entities: Dict[str, Numeric]) -> List[Device]:
+        transformed_entities = []
+
+        for k, v in entities.items():
+            sensor_id = f'serial:{k}'
             try:
-                self.serial_lock.release()
+                value = float(v)
-            except Exception as e:
+                entity_type = NumericSensor
-                self.logger.debug(e)
+            except (TypeError, ValueError):
+                value = v
+                entity_type = RawSensor
+
+            transformed_entities.append(
+                entity_type(
+                    id=sensor_id,
+                    name=k,
+                    value=value,
+                )
+            )
+
+        return [
+            Device(
+                id='serial',
+                name=self.device,
+                children=transformed_entities,
+            )
+        ]
+
+    @override
+    def main(self):
+        if not self._enable_polling:
+            # If the polling is disabled, we don't need to do anything here
+            self.wait_stop()
+            return
+
+        super().main()
+
+    @override
+    def stop(self):
+        super().stop()
+        self._close_serial()
 
 
 # vim:sw=4:ts=4:et:

platypush/plugins/serial/manifest.yaml

@@ -1,6 +1,8 @@
 manifest:
-  events: {}
+  events:
+    - platypush.message.event.sensor.SensorDataChangeEvent:
   install:
-    pip: []
+    pip:
+      - pyserial
   package: platypush.plugins.serial
   type: plugin

platypush/utils/__init__.py

@@ -5,6 +5,7 @@ import hashlib
 import importlib
 import inspect
 import logging
+from multiprocessing import Lock as PLock
 import os
 import pathlib
 import re
@@ -12,13 +13,15 @@ import signal
 import socket
 import ssl
 import urllib.request
-from typing import Optional, Tuple, Union
+from threading import Lock as TLock
+from typing import Generator, Optional, Tuple, Union
 
 from dateutil import parser, tz
 from redis import Redis
 from rsa.key import PublicKey, PrivateKey, newkeys
 
 logger = logging.getLogger('utils')
+Lock = Union[PLock, TLock]  # type: ignore
 
 
 def get_module_and_method_from_action(action):
@@ -363,7 +366,7 @@ def get_mime_type(resource: str) -> Optional[str]:
             return response.info().get_content_type()
     else:
         if hasattr(magic, 'detect_from_filename'):
-            mime = magic.detect_from_filename(resource)
+            mime = magic.detect_from_filename(resource)  # type: ignore
         elif hasattr(magic, 'from_file'):
             mime = magic.from_file(resource, mime=True)
         else:
@@ -372,7 +375,7 @@ def get_mime_type(resource: str) -> Optional[str]:
             )
 
         if mime:
-            return mime.mime_type if hasattr(mime, 'mime_type') else mime
+            return mime.mime_type if hasattr(mime, 'mime_type') else mime  # type: ignore
 
     return None
 
@@ -559,4 +562,29 @@ def to_datetime(t: Union[str, int, float, datetime.datetime]) -> datetime.dateti
     return t
 
 
+@contextlib.contextmanager
+def get_lock(
+    lock: Lock, timeout: Optional[float] = None
+) -> Generator[bool, None, None]:
+    """
+    Get a lock with an optional timeout through a context manager construct:
+
+        >>> from threading import Lock
+        >>> lock = Lock()
+        >>> with get_lock(lock, timeout=2):
+        >>>     ...
+
+    """
+    kwargs = {'timeout': timeout} if timeout else {}
+    result = lock.acquire(**kwargs)
+
+    try:
+        if not result:
+            raise TimeoutError()
+        yield result
+    finally:
+        if result:
+            lock.release()
+
+
 # vim:sw=4:ts=4:et:

tests/utils.py

@@ -1,7 +1,8 @@
 import os
-import requests
 from typing import Optional
 
+import requests
+
 from platypush.message import Message
 from platypush.message.response import Response
 from platypush.utils import set_timeout, clear_timeout
@@ -36,12 +37,19 @@ class TimeoutException(RuntimeError):
     """
     Exception raised in case of timeout.
     """
+
     def __init__(self, msg: str = 'Timeout'):
         self.msg = msg
 
 
-def send_request(action: str, timeout: Optional[float] = None, args: Optional[dict] = None,
+def send_request(
-                 parse_json: bool = True, authenticate: bool = True, **kwargs):
+    action: str,
+    timeout: Optional[float] = None,
+    args: Optional[dict] = None,
+    parse_json: bool = True,
+    authenticate: bool = True,
+    **kwargs
+):
     if not timeout:
         timeout = request_timeout
     if not args:
@@ -56,7 +64,8 @@ def send_request(action: str, timeout: Optional[float] = None, args: Optional[di
             'type': 'request',
             'action': action,
             'args': args,
-        }, **kwargs
+        },
+        **kwargs
     )
 
     clear_timeout()
@@ -71,23 +80,33 @@ def register_user(username: Optional[str] = None, password: Optional[str] = None
         username = test_user
         password = test_pass
 
-    set_timeout(seconds=request_timeout, on_timeout=on_timeout('User registration response timed out'))
+    set_timeout(
-    response = requests.post('{base_url}/register?redirect={base_url}/'.format(base_url=base_url), data={
+        seconds=request_timeout,
+        on_timeout=on_timeout('User registration response timed out'),
+    )
+    response = requests.post(
+        '{base_url}/register?redirect={base_url}/'.format(base_url=base_url),
+        data={
             'username': username,
             'password': password,
             'confirm_password': password,
-    })
+        },
+    )
 
     clear_timeout()
     return response
 
 
 def on_timeout(msg):
-    def _f(): raise TimeoutException(msg)
+    def _f():
+        raise TimeoutException(msg)
+
     return _f
 
 
 def parse_response(response):
     response = Message.build(response.json())
-    assert isinstance(response, Response), 'Expected Response type, got {}'.format(response.__class__.__name__)
+    assert isinstance(response, Response), 'Expected Response type, got {}'.format(
+        response.__class__.__name__
+    )
     return response