diff --git a/adafruit_debouncer.py b/adafruit_debouncer.py
index 868a217..67037f7 100644
--- a/adafruit_debouncer.py
+++ b/adafruit_debouncer.py
@@ -31,20 +31,31 @@
 from micropython import const
 from adafruit_ticks import ticks_ms, ticks_diff
 
-_DEBOUNCED_STATE = const(0x01)
-_UNSTABLE_STATE = const(0x02)
-_CHANGED_STATE = const(0x04)
+try:
+    from typing import Callable, Optional, Union
+    from circuitpython_typing.io import ROValueIO
+except ImportError:
+    pass
 
-_TICKS_PER_SEC = const(1000)
+_DEBOUNCED_STATE: int = const(0x01)
+_UNSTABLE_STATE: int = const(0x02)
+_CHANGED_STATE: int = const(0x04)
+
+_TICKS_PER_SEC: int = const(1000)
 
 
 class Debouncer:
     """Debounce an input pin or an arbitrary predicate"""
 
-    def __init__(self, io_or_predicate, interval=0.010):
+    def __init__(
+        self,
+        io_or_predicate: Union[ROValueIO, Callable[[], bool]],
+        interval: float = 0.010,
+    ) -> None:
         """Make an instance.
-        :param DigitalInOut/function io_or_predicate: the DigitalIO or function to debounce
-        :param int interval: bounce threshold in seconds (default is 0.010, i.e. 10 milliseconds)
+        :param DigitalInOut/function io_or_predicate: the DigitalIO or
+                                                      function that returns a boolean to debounce
+        :param float interval: bounce threshold in seconds (default is 0.010, i.e. 10 milliseconds)
         """
         self.state = 0x00
         if hasattr(io_or_predicate, "value"):
@@ -59,21 +70,21 @@ def __init__(self, io_or_predicate, interval=0.010):
 
         # Could use the .interval setter, but pylint prefers that we explicitly
         # set the real underlying attribute:
-        self._interval_ticks = interval * _TICKS_PER_SEC
+        self._interval_ticks = int(interval * _TICKS_PER_SEC)
 
-    def _set_state(self, bits):
+    def _set_state(self, bits: int) -> None:
         self.state |= bits
 
-    def _unset_state(self, bits):
+    def _unset_state(self, bits: int) -> None:
         self.state &= ~bits
 
-    def _toggle_state(self, bits):
+    def _toggle_state(self, bits: int) -> None:
         self.state ^= bits
 
-    def _get_state(self, bits):
+    def _get_state(self, bits: int) -> bool:
         return (self.state & bits) != 0
 
-    def update(self, new_state=None):
+    def update(self, new_state: Optional[int] = None) -> None:
         """Update the debouncer state. MUST be called frequently"""
         now_ticks = ticks_ms()
         self._unset_state(_CHANGED_STATE)
@@ -96,38 +107,38 @@ def update(self, new_state=None):
                     self._state_changed_ticks = now_ticks
 
     @property
-    def interval(self):
+    def interval(self) -> float:
         """The debounce delay, in seconds"""
         return self._interval_ticks / _TICKS_PER_SEC
 
     @interval.setter
-    def interval(self, new_interval_s):
+    def interval(self, new_interval_s: float) -> None:
         self._interval_ticks = new_interval_s * _TICKS_PER_SEC
 
     @property
-    def value(self):
+    def value(self) -> bool:
         """Return the current debounced value."""
         return self._get_state(_DEBOUNCED_STATE)
 
     @property
-    def rose(self):
+    def rose(self) -> bool:
         """Return whether the debounced value went from low to high at the most recent update."""
         return self._get_state(_DEBOUNCED_STATE) and self._get_state(_CHANGED_STATE)
 
     @property
-    def fell(self):
+    def fell(self) -> bool:
         """Return whether the debounced value went from high to low at the most recent update."""
         return (not self._get_state(_DEBOUNCED_STATE)) and self._get_state(
             _CHANGED_STATE
         )
 
     @property
-    def last_duration(self):
+    def last_duration(self) -> float:
         """Return the number of seconds the state was stable prior to the most recent transition."""
         return self._last_duration_ticks / _TICKS_PER_SEC
 
     @property
-    def current_duration(self):
+    def current_duration(self) -> float:
         """Return the number of seconds since the most recent transition."""
         return ticks_diff(ticks_ms(), self._state_changed_ticks) / _TICKS_PER_SEC
 
@@ -148,12 +159,12 @@ class Button(Debouncer):
 
     def __init__(
         self,
-        pin,
-        short_duration_ms=200,
-        long_duration_ms=500,
-        value_when_pressed=False,
+        pin: Union[ROValueIO, Callable[[], bool]],
+        short_duration_ms: int = 200,
+        long_duration_ms: int = 500,
+        value_when_pressed: bool = False,
         **kwargs
-    ):
+    ) -> None:
         self.short_duration_ms = short_duration_ms
         self.long_duration_ms = long_duration_ms
         self.value_when_pressed = value_when_pressed
@@ -165,20 +176,20 @@ def __init__(
         super().__init__(pin, **kwargs)
 
     @property
-    def pressed(self):
+    def pressed(self) -> bool:
         """Return whether the button was pressed or not at the last update."""
         return (self.value_when_pressed and self.rose) or (
             not self.value_when_pressed and self.fell
         )
 
     @property
-    def released(self):
+    def released(self) -> bool:
         """Return whether the button was release or not at the last update."""
         return (self.value_when_pressed and self.fell) or (
             not self.value_when_pressed and self.rose
         )
 
-    def update(self, new_state=None):
+    def update(self, new_state: Optional[int] = None) -> None:
         super().update(new_state)
         if self.pressed:
             self.last_change_ms = ticks_ms()
@@ -210,12 +221,12 @@ def update(self, new_state=None):
                 self.short_to_show = 0
 
     @property
-    def short_count(self):
+    def short_count(self) -> int:
         """Return the number of short press if a series of short presses has
         ended at the last update."""
         return self.short_to_show
 
     @property
-    def long_press(self):
+    def long_press(self) -> bool:
         """Return whether a long press has occured at the last update."""
         return self.long_to_show