Added PCA9685 PWM driver plugin

CHANGELOG.md

@@ -19,6 +19,8 @@ Given the high speed of development in the first phase, changes are being report
 - Added generic joystick backend `backend.joystick.jstest` which uses `jstest` from the
   standard `joystick` system package to read the state of joysticks not compatible with
   `python-inputs`.
+  
+- Added PWM PCA9685 plugin.
 
 ### Changed
 

platypush/plugins/pwm/pca9685.py

@@ -0,0 +1,120 @@
+import time
+from typing import Optional, Dict
+
+from platypush.plugins import Plugin, action
+
+
+class PwmPca9685Plugin(Plugin):
+    """
+    This plugin interacts with an `Adafruit PCA9685 <https://learn.adafruit.com/16-channel-pwm-servo-driver?view=all>`_
+    circuit, a 16-channel PWM servo driver. You can leverage this plugin to control servos and motors through Platypush.
+
+    Note that the driver for PCA9685 has been written for CircuitPython, and in order to use it on a Raspberry Pi or
+    similar devices you need to
+    `follow these steps <https://learn.adafruit.com/16-channel-pwm-servo-driver?view=all#python-circuitpython>`_::
+
+        # pip3 install --upgrade adafruit-python-shell
+        $ wget https://raw.githubusercontent.com/adafruit/Raspberry-Pi-Installer-Scripts/master/raspi-blinka.py
+        # python3 raspi-blinka.py
+
+    Then reboot and check that the following virtual devices are available::
+
+        - /dev/i2c-1
+        - /dev/spidev0.0
+        - /dev/spidev0.1
+
+    Finally, install the PCA9685 drivers::
+
+        # pip3 install --upgrade adafruit-circuitpython-pca9685
+
+    This plugin works with a PCA9685 circuit connected to the Platypush host over I2C interface.
+    """
+
+    MIN_PWM_VALUE = 0
+    MAX_PWM_VALUE = 0xffff
+
+    def __init__(self, frequency: float, step_value: float = 0.1, step_duration: float = 0.05, **kwargs):
+        """
+        :param frequency: Default PWM frequency to use for the driver, in Hz.
+        :param step_value: How much each channel value should be increased/decreased on each step.
+        :param step_duration: Length of each step transient when writing PWM values (default: 0.05 seconds).
+        """
+        super().__init__(**kwargs)
+        self.frequency = frequency
+        self.step_value = step_value
+        self.step_duration = step_duration
+        self._pca = None
+
+    @staticmethod
+    def _convert_percent_to_duty_cycle(value: float) -> int:
+        """
+        Convert a duty cycle percentage value to a PCA9685 value between 0 and `0xffff`.
+
+        :param value: Duty cycle value, between 0 and 1.
+        :return: Duty cycle 16-bit value, between 0 and `0xffff`.
+        """
+        return int(value * 65535)
+
+    @action
+    def execute(self, channels: Dict[int, float], frequency: Optional[float] = None, step_value: Optional[float] = None,
+                step_duration: Optional[float] = None):
+        """
+        Send PWM values to the specified channels.
+
+        :param channels: Map of the values to be written, as ``channel_index -> value``, where value is a real number
+            between 0.0 (minimum duty cycle) and 1.0 (maximum duty cycle).
+        :param frequency: Override default frequency.
+        :param step_value: Override default step value.
+        :param step_duration: Override default step duration.
+        """
+        import busio
+        from board import SCL, SDA
+        from adafruit_pca9685 import PCA9685
+
+        values = {k: self._convert_percent_to_duty_cycle(v) for k, v in channels.items()}
+        step_value = self._convert_percent_to_duty_cycle(step_value if step_value is not None else self.step_value)
+        step_duration = step_duration if step_duration is not None else self.step_duration
+        i2c_bus = busio.I2C(SCL, SDA)
+        pca = self._pca or PCA9685(i2c_bus)
+        pca.frequency = frequency or self.frequency
+        self._pca = pca
+        done = False
+
+        while not done:
+            done = True
+
+            for channel, value in values.items():
+                if value == pca.channels[channel].duty_cycle:
+                    continue
+
+                done = False
+                if value > pca.channels[channel].duty_cycle:
+                    pca.channels[channel].duty_cycle = min(pca.channels[channel].duty_cycle + step_value,
+                                                           self.MAX_PWM_VALUE)
+                else:
+                    pca.channels[channel].duty_cycle = max(pca.channels[channel].duty_cycle - step_value,
+                                                           self.MIN_PWM_VALUE)
+
+            time.sleep(step_duration)
+
+    @action
+    def deinit(self):
+        """
+        De-initialize the PCA9685 if it was previously initialized.
+        """
+        if not self._pca:
+            self.logger.warning('The PCA9685 driver is not initialized')
+            return
+
+        self._pca.deinit()
+
+    @action
+    def reset(self):
+        """
+        Reset the PCA9685 (set all the channels to zero).
+        """
+        if not self._pca:
+            self.logger.warning('The PCA9685 driver is not initialized')
+            return
+
+        self._pca.reset()

requirements.txt

@@ -317,3 +317,7 @@ croniter
 
 # Support for file.monitor backend
 #watchdog
+
+# Support for Adafruit PCA9685 PWM controller
+#adafruit-python-shell
+#adafruit-circuitpython-pca9685

setup.py

@@ -249,5 +249,7 @@ setup(
         'smartthings': ['pysmartthings', 'aiohttp'],
         # Support for file.monitor backend
         'filemonitor': ['watchdog'],
+        # Support for Adafruit PCA9685 PWM controller
+        'pca9685': ['adafruit-python-shell', 'adafruit-circuitpython-pca9685'],
     },
 )