Add rotaryio module

src/rotaryio.py

@@ -0,0 +1,137 @@
+# SPDX-FileCopyrightText: 2025 Melissa LeBlanc-Williams for Adafruit Industries
+#
+# SPDX-License-Identifier: MIT
+"""
+`rotaryio` - Support for reading rotation sensors
+===========================================================
+See `CircuitPython:rotaryio` in CircuitPython for more details.
+
+* Author(s): Melissa LeBlanc-Williams
+"""
+
+from __future__ import annotations
+import threading
+import microcontroller
+import digitalio
+
+# Define the state transition table for the quadrature encoder
+transitions = [
+    0,  # 00 -> 00 no movement
+    -1,  # 00 -> 01 3/4 ccw (11 detent) or 1/4 ccw (00 at detent)
+    +1,  # 00 -> 10 3/4 cw or 1/4 cw
+    0,  # 00 -> 11 non-Gray-code transition
+    +1,  # 01 -> 00 2/4 or 4/4 cw
+    0,  # 01 -> 01 no movement
+    0,  # 01 -> 10 non-Gray-code transition
+    -1,  # 01 -> 11 4/4 or 2/4 ccw
+    -1,  # 10 -> 00 2/4 or 4/4 ccw
+    0,  # 10 -> 01 non-Gray-code transition
+    0,  # 10 -> 10 no movement
+    +1,  # 10 -> 11 4/4 or 2/4 cw
+    0,  # 11 -> 00 non-Gray-code transition
+    +1,  # 11 -> 01 1/4 or 3/4 cw
+    -1,  # 11 -> 10 1/4 or 3/4 ccw
+    0,  # 11 -> 11 no movement
+]
+
+
+class IncrementalEncoder:
+    """
+    IncrementalEncoder determines the relative rotational position based on two series of
+    pulses. It assumes that the encoder’s common pin(s) are connected to ground,and enables
+    pull-ups on pin_a and pin_b.
+
+    Create an IncrementalEncoder object associated with the given pins. It tracks the
+    positional state of an incremental rotary encoder (also known as a quadrature encoder.)
+    Position is relative to the position when the object is constructed.
+    """
+
+    def __init__(
+        self, pin_a: microcontroller.Pin, pin_b: microcontroller.Pin, divisor: int = 4
+    ):
+        """
+        Create an IncrementalEncoder object associated with the given pins. It tracks the
+        positional state of an incremental rotary encoder (also known as a quadrature encoder.)
+        Position is relative to the position when the object is constructed.
+
+        :param microcontroller.Pin pin_a: The first pin connected to the encoder.
+        :param microcontroller.Pin pin_b: The second pin connected to the encoder.
+        :param int divisor: The number of pulses per encoder step. Default is 4.
+        """
+        self._pin_a = digitalio.DigitalInOut(pin_a)
+        self._pin_a.switch_to_input(pull=digitalio.Pull.UP)
+        self._pin_b = digitalio.DigitalInOut(pin_b)
+        self._pin_b.switch_to_input(pull=digitalio.Pull.UP)
+        self._position = 0
+        self._last_state = 0
+        self._divisor = divisor
+        self._sub_count = 0
+        self._poll_thread = threading.Thread(target=self._polling_loop, daemon=True)
+        self._poll_thread.start()
+
+    def deinit(self):
+        """Deinitializes the IncrementalEncoder and releases any hardware resources for reuse."""
+        self._pin_a.deinit()
+        self._pin_b.deinit()
+        if self._poll_thread.is_alive():
+            self._poll_thread.join()
+
+    def __enter__(self) -> IncrementalEncoder:
+        """No-op used by Context Managers."""
+        return self
+
+    def __exit__(self, _type, _value, _traceback):
+        """
+        Automatically deinitializes when exiting a context. See
+        :ref:`lifetime-and-contextmanagers` for more info.
+        """
+        self.deinit()
+
+    @property
+    def divisor(self) -> int:
+        """The divisor of the quadrature signal. Use 1 for encoders without detents, or encoders
+        with 4 detents per cycle. Use 2 for encoders with 2 detents per cycle. Use 4 for encoders
+        with 1 detent per cycle."""
+        return self._divisor
+
+    @divisor.setter
+    def divisor(self, value: int):
+        self._divisor = value
+
+    @property
+    def position(self) -> int:
+        """The current position in terms of pulses. The number of pulses per rotation is defined
+        by the specific hardware and by the divisor."""
+        return self._position
+
+    @position.setter
+    def position(self, value: int):
+        self._position = value
+
+    def _get_pin_state(self) -> int:
+        """Returns the current state of the pins."""
+        return self._pin_a.value << 1 | self._pin_b.value
+
+    def _polling_loop(self):
+        while True:
+            self._poll_encoder()
+
+    def _poll_encoder(self):
+        # Check the state of the pins
+        # if either pin has changed, update the state
+        new_state = self._get_pin_state()
+        if new_state != self._last_state:
+            self._state_update(new_state)
+            self._last_state = new_state
+
+    def _state_update(self, new_state: int):
+        new_state &= 3
+        index = self._last_state << 2 | new_state
+        sub_increment = transitions[index]
+        self._sub_count += sub_increment
+        if self._sub_count >= self._divisor:
+            self._position += 1
+            self._sub_count = 0
+        elif self._sub_count <= -self._divisor:
+            self._position -= 1
+            self._sub_count = 0