New Sensor Module: Frequency Counter (#378)

* Add generic Frequency Counter Module

README.md

@@ -46,8 +46,10 @@ Hardware support is provided by specific GPIO, Sensor and Stream modules. It's e
   - PMS5003 particulate sensor (`pms5003`)
   - SHT40/SHT41/SHT45 temperature and humidity sensors (`sht4x`)
   - YF-S201 flow rate sensor (`yfs201`)
+  - FREQUENCYCOUNTER Counts pulses from GPIOs and return the frequency in Hz (frequencycounter)
   - FLOWSENSOR generic flow rate sensor like YF-S201 or YF-DN50 (`flowsensor`)
 
+
 ### Streams
 
   - Serial port (`serial`)

mqtt_io/modules/sensor/frequencycounter.py

@@ -0,0 +1,93 @@
+"""
+
+Frequencycounter: Generic Frequency Counter
+
+Example configuration:
+
+sensor_modules:
+  - name: frequency
+    module: frequencycounter
+
+sensor_inputs:
+  - name: flow_rate1
+    module: frequency
+    pin: 0
+    digits: 0
+    interval: 10
+
+"""
+
+from typing import Dict
+from ...types import CerberusSchemaType, ConfigType, SensorValueType
+from . import GenericSensor
+
+REQUIREMENTS = ("gpiozero",)
+
+
+class FREQUENCYCOUNTER:
+    """
+    Frequency Counter class
+    Multiple instances support multiple sensors on different pins
+    """
+
+    def __init__(self, gpiozero, name: str, pin: int) -> None: # type: ignore[no-untyped-def]
+        self.name = name
+        self.pin = gpiozero.DigitalInputDevice(pin)
+        self.pin.when_activated = self.count_pulse
+        self.count = 0
+
+    def count_pulse(self) -> None:
+        """Increment pulse count."""
+        self.count += 1
+
+    def reset_count(self) -> None:
+        """Reset pulse count."""
+        self.count = 0
+
+    def frequency(self, sample_window: int) -> float:
+        """
+        sample_window is in seconds, so hz is pulse_count / sample_window
+        """
+        hertz = self.count / sample_window
+        return hertz
+
+    def get_value(self, interval: int) -> float:
+        """Return frequency over interval seconds and reset count."""
+        frequency = self.frequency(interval)
+        self.reset_count()
+        return frequency
+
+
+class Sensor(GenericSensor):
+    """
+    Frequency Counter
+    """
+
+    SENSOR_SCHEMA: CerberusSchemaType = {
+        "pin": {
+            "type": 'integer',
+            "required": True,
+            "empty": False,
+        },
+        "interval": {
+            "type": 'integer',
+            "required": True,
+            "empty": False,
+        }
+    }
+
+    def setup_module(self) -> None:
+        # pylint: disable=import-outside-toplevel,import-error
+        import gpiozero  # type: ignore
+
+        self.gpiozero = gpiozero
+        self.sensors: Dict[str, FREQUENCYCOUNTER] = {}
+
+    def setup_sensor(self, sens_conf: ConfigType) -> None:
+        sensor = FREQUENCYCOUNTER(
+            gpiozero=self.gpiozero, name=sens_conf["name"], pin=sens_conf["pin"]
+        )
+        self.sensors[sensor.name] = sensor
+
+    def get_value(self, sens_conf: ConfigType) -> SensorValueType:
+        return self.sensors[sens_conf["name"]].get_value(sens_conf["interval"])