Add NeXT standalone mouse code

CircuitPython_NeXT_Mouse_RP2040/code.py

@@ -0,0 +1,45 @@
+# SPDX-FileCopyrightText: 2023 Jeff Epler for Adafruit Industries
+# SPDX-License-Identifier: MIT
+import board
+import digitalio
+import rotaryio
+from adafruit_hid.mouse import Mouse
+from usb_hid import devices
+
+SCALE = 4
+
+class RelativeEncoder:
+    def __init__(self, pin_a, pin_b, divisor=1):
+        self._encoder = rotaryio.IncrementalEncoder(pin_a, pin_b, divisor)
+        self._old = self._encoder.position
+
+    @property
+    def delta(self):
+        old = self._old
+        new = self._old = self._encoder.position
+        return new - old
+
+xpos = RelativeEncoder(board.A0, board.A1)
+ypos = RelativeEncoder(board.A2, board.A3)
+lmb = digitalio.DigitalInOut(board.SCL)
+lmb.pull = digitalio.Pull.UP
+rmb = digitalio.DigitalInOut(board.SDA)
+rmb.pull = digitalio.Pull.UP
+
+mouse = Mouse(devices)
+
+while True:
+    dx = xpos.delta * SCALE
+    dy = ypos.delta * SCALE
+    l = not lmb.value
+    r = not rmb.value
+    mouse.report[0] = (
+        mouse.MIDDLE_BUTTON if (l and r) else
+        mouse.LEFT_BUTTON if l else
+        mouse.RIGHT_BUTTON if r else
+        0)
+
+    if dx or dy:
+        mouse.move(dx, dy)
+    else:
+        mouse._send_no_move() # pylint: disable=protected-access