Driver for Buttons or Switches

switch.py

+"""
+    class for mechanical switches (micro switches, push buttons and alike)
+    with rudimentary support for debouncing.
+    The Pins for the switches are configured as Pin.IN and Pin.PULL_UP.
+    The (normally-open) switches are supposed to make ground contact
+    (falling interrupts are used).
+"""
+
+from machine import Pin
+from time import ticks_ms
+
+class Switch(object):
+    def __init__(self, switch):
+        """ <switch> (number) GPIO pin """
+        self._pin = switch                          # pin number
+        self._switch = Pin(switch, Pin.IN, Pin.PULL_UP)
+        self._switch_interrupt = False              # set by switch-ISR, reset by switch() method
+        self._debounce_ticks_ms = ticks_ms()        # remember last switch interrupt time
+        try:                                        # choose for 'hard' interrupt if supported
+            self._interrupt = self._switch.irq(trigger=Pin.IRQ_FALLING, handler=self._callback, hard=True)
+        except TypeError:
+            self._interrupt = self._switch.irq(trigger=Pin.IRQ_FALLING, handler=self._callback)
+
+    def _callback(self, switch):
+        """ Pin interrupt service routine """
+        tick_delta = ticks_ms() - self._debounce_ticks_ms   #
+        # print(f"pin {self._pin} interrupt {tick_delta} status {self._switch.value()}")
+        if tick_delta > 200:                        # skip switch bounces
+            # print(f"pin {self._pin} debounced {tick_delta}")
+            self._switch_interrupt = True           # mark 'interrupt occurred'
+            self._debounce_ticks_ms = ticks_ms()    # update time of last accepted interrupt
+
+    def switch(self):
+        """ Indicator of Pin interrupt
+            True: interrupt occurred since last poll, False: not!
+        """
+        if self._switch_interrupt:
+            self._switch_interrupt = False          # user is aware of interrupt
+            return True                             # signal switch interrupt
+        return False
+
+    def __call__(self):
+        # make instance callable (for convenience!)
+        return self.switch()                          # Pin.value()