Add rotaryencoder example

examples/rotaryencoder.py

@@ -0,0 +1,119 @@
+# SPDX-FileCopyrightText: 2021 Jeff Epler, written for Adafruit Industries
+#
+# SPDX-License-Identifier: MIT
+#
+# This example is adapted in part from micropython:
+# https://github.com/micropython/micropython/pull/6894/files
+
+import adafruit_pioasm
+import board
+import rp2pio
+import array
+import digitalio
+
+
+class IncrementalEncoder:
+    _state_look_up_table = array.array(
+        "b",
+        [
+            # Direction = 1
+            0,  # 00 to 00
+            -1,  # 00 to 01
+            +1,  # 00 to 10
+            +2,  # 00 to 11
+            +1,  # 01 to 00
+            0,  # 01 to 01
+            +2,  # 01 to 10
+            -1,  # 01 to 11
+            -1,  # 10 to 00
+            +2,  # 10 to 01
+            0,  # 10 to 10
+            +1,  # 10 to 11
+            +2,  # 11 to 00
+            +1,  # 11 to 01
+            -1,  # 11 to 10
+            0,  # 11 to 11
+            # Direction = 0
+            0,  # 00 to 00
+            -1,  # 00 to 01
+            +1,  # 00 to 10
+            -2,  # 00 to 11
+            +1,  # 01 to 00
+            0,  # 01 to 01
+            -2,  # 01 to 10
+            -1,  # 01 to 11
+            -1,  # 10 to 00
+            -2,  # 10 to 01
+            0,  # 10 to 10
+            +1,  # 10 to 11
+            -2,  # 11 to 00
+            +1,  # 11 to 01
+            -1,  # 11 to 10
+            0,  # 11 to 11
+        ],
+    )
+
+    _sm_code = adafruit_pioasm.assemble(
+        """
+    again:
+        in pins, 2
+        mov x, isr
+        jmp x!=y, push_data
+        mov isr, null
+        jmp again
+    push_data:
+        push
+        mov y, x
+    """
+    )
+
+    _sm_init = adafruit_pioasm.assemble("set y 31")
+
+    def __init__(self, pin_a, pin_b):
+        if not rp2pio.pins_are_sequential([pin_a, pin_b]):
+            raise ValueError("Pins must be sequential")
+
+        self._sm = rp2pio.StateMachine(
+            self._sm_code,
+            160_000,
+            init=self._sm_init,
+            first_in_pin=pin_a,
+            in_pin_count=2,
+            pull_in_pin_up=0b11,
+            in_shift_right=False,
+        )
+
+        self._counter = 0
+        self._direction = 0
+        self._lut_index = 0
+        self._buffer = bytearray(1)
+
+    def _update_state_machine(self, state):
+        lut_index = self._lut_index | (state & 3)
+        lut = self._state_look_up_table[lut_index]
+        self._counter += lut
+        if lut:
+            self._direction = 1 if (lut > 0) else 0
+        self._lut_index = ((lut_index << 2) & 0b1100) | (self._direction << 4)
+
+    def deinit(self):
+        self._sm.deinit()
+
+    @property
+    def value(self):
+        while self._sm.in_waiting:
+            self._sm.readinto(self._buffer)
+            self._update_state_machine(self._buffer[0])
+        return self._counter
+
+
+encoder = IncrementalEncoder(board.GP2, board.GP3)
+
+old_value = None
+while True:
+    gen()
+
+    value = encoder.value
+    if old_value != value:
+        print("Encoder:", value)
+        old_value = value