[#212] Support for asynchronous event monitoring on the GPIO plugin

platypush/message/event/gpio/__init__.py

@@ -0,0 +1,17 @@
+from typing import Union
+
+from platypush.message.event import Event
+
+
+class GPIOEvent(Event):
+    """
+    Event triggered when the value on a GPIO PIN changes.
+    """
+
+    def __init__(self, pin: Union[int, str], value: int, *args, **kwargs):
+        """
+        :param pin: PIN number or name.
+        :param value: Current value of the PIN.
+        """
+        super().__init__(*args, pin=pin, value=value, **kwargs)
+

platypush/plugins/__init__.py

@@ -88,7 +88,8 @@ class RunnablePlugin(Plugin):
         if self._thread and self._thread.is_alive():
             self.logger.info(f'Waiting for {self.__class__.__name__} to stop')
             try:
-                self._thread.join()
+                if self._thread:
+                    self._thread.join()
             except Exception as e:
                 self.logger.warning(f'Could not join thread on stop: {e}')
 

platypush/plugins/gpio/__init__.py

@@ -3,35 +3,58 @@
 """
 
 import threading
-from typing import Any, Optional, Dict, Union
+from typing import Any, Optional, Dict, Union, Collection
 
-from platypush.plugins import Plugin, action
+from platypush.context import get_bus
+from platypush.message.event.gpio import GPIOEvent
+from platypush.plugins import RunnablePlugin, action
 
 
-class GpioPlugin(Plugin):
+class GpioPlugin(RunnablePlugin):
     """
-    Plugin to handle raw read/write operation on the Raspberry Pi GPIO pins.
+    This plugin can be used to interact with custom electronic devices
+    connected to a Raspberry Pi (or compatible device) over GPIO pins.
 
     Requires:
 
         * **RPi.GPIO** (``pip install RPi.GPIO``)
+
+    Triggers:
+
+        * :class:`platypush.message.event.gpio.GPIOEvent` when the value of a
+            monitored PIN changes.
+
     """
 
-    def __init__(self, pins: Optional[Dict[str, int]] = None, mode: str = 'board', **kwargs):
+    def __init__(
+            self,
+            pins: Optional[Dict[str, int]] = None,
+            monitored_pins: Optional[Collection[Union[str, int]]] = None,
+            mode: str = 'board',
+            **kwargs
+    ):
         """
-        :param mode: Specify 'board' if you want to use the board PIN numbers,
-            'bcm' for Broadcom PIN numbers (default: 'board')
-        :param pins: Configuration for the GPIO PINs as a name -> pin_number map.
+        :param mode: Specify ``board`` if you want to use the board PIN numbers,
+            ``bcm`` for Broadcom PIN numbers (default: ``board``)
+        :param pins: Custom `GPIO name` -> `PIN number` mapping. This can be
+            useful if you want to reference your GPIO ports by name instead
+            of PIN number.
 
-        Example::
+        Example:
 
-            {
-                "LED_1": 14,
-                "LED_2": 15,
-                "MOTOR": 16,
-                "SENSOR": 17
-            }
+          .. code-block:: yaml
 
+            pins:
+                LED_1: 14,
+                LED_2: 15,
+                MOTOR: 16,
+                SENSOR_1: 17
+                SENSOR_2: 18
+
+        :param monitored_pins: List of PINs to monitor. If a new value is detected
+            on these pins then a :class:`platypush.message.event.gpio.GPIOEvent`
+            event will be triggered. GPIO PINS can be referenced either by number
+            or name, if a name is specified on the `pins` argument.
         """
 
         super().__init__(**kwargs)
@@ -39,6 +62,7 @@ class GpioPlugin(Plugin):
         self._initialized = False
         self._init_lock = threading.RLock()
         self._initialized_pins = {}
+        self._monitored_pins = monitored_pins or []
         self.pins_by_name = pins if pins else {}
         self.pins_by_number = {number: name
                                for (name, number) in self.pins_by_name.items()}
@@ -71,6 +95,31 @@ class GpioPlugin(Plugin):
         assert mode_str in ['BOARD', 'BCM'], 'Invalid mode: {}'.format(mode_str)
         return getattr(GPIO, mode_str)
 
+    def on_gpio_event(self):
+        def callback(pin: int):
+            import RPi.GPIO as GPIO
+            value = GPIO.input(pin)
+            pin = self.pins_by_number.get(pin, pin)
+            get_bus().post(GPIOEvent(pin=pin, value=value))
+
+        return callback
+
+    def main(self):
+        import RPi.GPIO as GPIO
+        if not self._monitored_pins:
+            return  # No need to start the monitor
+
+        self._init_board()
+        monitored_pins = [
+            self._get_pin_number(pin) for pin in self._monitored_pins
+        ]
+
+        for pin in monitored_pins:
+            GPIO.setup(pin, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)
+            GPIO.add_event_detect(pin, GPIO.BOTH, callback=self.on_gpio_event())
+
+        self._should_stop.wait()
+
     @action
     def write(self, pin: Union[int, str], value: Union[int, bool],
               name: Optional[str] = None) -> Dict[str, Any]:

platypush/plugins/gpio/manifest.yaml

@@ -1,5 +1,7 @@
 manifest:
-  events: {}
+  events:
+    - platypush.message.event.gpio.GPIOEvent:
+        When the value of a monitored PIN changes.
   install:
     pip:
     - RPi.GPIO