initial hall sensor support

software/libraries/hall_speed.py

@@ -1,28 +1,78 @@
 from micropython import const
 import machine
 import time
+import math
 
-#a class abstraction for a digital hall effect sensor used as a rev counter
+# a class abstraction for a digital hall effect sensor used as a rev counter
 
 class hall():
 
     def __init__(self, pin, diameter, scale):
+        """Initialize the hall effect sensor
+
+        Arguments:
+        pin      -- pin number that the hall effect sensor is connected to
+        diameter -- wheel diameter in centimeters
+        scale    -- the scale factor of how many revolutions of the magnet per revolution of the tire
+        """
+
         self.pin = machine.Pin(pin)
-        self.scale = scale*diameter #the scale factor of how many revolutions of the magnet per revolution of the tire
-        self.ticks = time.ticks_us();
-        self.period_us = 0
-
-    def update_period(self):
-        t = time.ticks_us()
-        period_us = time.ticks_diff(self.ticks, t)
-        self.ticks = t()
-
+        self.diameter_scaled = scale*diameter # Scale the diameter.
+        self.ticks = time.ticks_ms() # Take the current ticks (milliseconds).
+
+        # Create an array for the moving average.
+        self.readings = [None] * 5
+
+        # Configure the IRQ for the hall effect sensor pin.
+        self.pin.irq(trigger=machine.Pin.IRQ_RISING, handler=self.rpm_event)
+
+
+    def rpm_event(self, pin):
+        """Calculate RPM and store it in the array"""
+        t = time.ticks_ms() # Get the current ticks (milliseconds).
+        period_ms = time.ticks_diff(t, self.ticks) # Calculate the time since last reading.
+
+        # RPM is calculated as 1 minute (60 * 1000ms) divided by the period_ms.
+        # For example, if period_ms is 60,000, then RPM is 1.
+        rpm = (60*1000)/period_ms
+
+        # Add this reading to the array and pull the first value off the array.
+        self.readings = (self.readings + [rpm])[1:]
+
+        print(self.readings)
+        self.ticks = time.ticks_ms() # Store the current ticks.
+
+
     def get_rpm(self):
-        return(1000000/self.period_us);
-
-    def get_speed(self):
-        return(self.get_rpm()*scale)
-
+        """Get the current RPM reading.
+
+        Returns
+        -1 if there are no readings yet
+        The rolling average RPM value
+        """
+
+        # Don't try to add any None values in the array
+        readings = [x for x in self.readings if x is not None]
+        if len(readings) > 0:
+            return(sum(readings)/len(readings))
+        else:
+            return -1
+
+
+    def get_speed_cm_per_minute(self):
+        return(self.get_rpm()*self.diameter_scaled*math.pi)
+
+
     def get_speed_kph(self):
-        return(self.get_speed()*1.6)
-
+        km_per_minute = self.get_speed_cm_per_minute()/100000
+        return km_per_minute*60
+
+
+if __name__ == '__main__':
+    hall = hall(19, 60, 1)
+    while(True):
+        print(hall.get_rpm())
+        print(f"Speed (cm/min): {hall.get_speed_cm_per_minute()}")
+        print(f"Speed (kph): {hall.get_speed_kph()}")
+        time.sleep(1)
+        #print(machine.Pin(19).value())