Custom matrix scanners

- Introduce Scanner base class for MatrixScanner
- Create new Scanner using built-in keypad module
- Allow overriding the scanner used by KMKKeyboard

kmk/scanners/__init__.py

@@ -0,0 +1,12 @@
+class Scanner:
+    '''
+    Base class for scanners.
+    '''
+
+    def scan_for_changes(self):
+        '''
+        Scan for key events and return a key report if an event exists.
+
+        The key report is a byte array with contents [row, col, True if pressed else False]
+        '''
+        pass

kmk/scanners/native_keypad_scanner.py

@@ -0,0 +1,60 @@
+import keypad
+
+from kmk.matrix import DiodeOrientation
+from kmk.scanners import Scanner
+
+
+class NativeKeypadScanner(Scanner):
+    '''
+    Translation layer around a CircuitPython 7 keypad scanner.
+
+    :param pin_map: A sequence of (row, column) tuples for each key.
+    :param kp: An instance of the keypad class.
+    '''
+
+    def __init__(self, pin_map, kp):
+        self.pin_map = pin_map
+        self.keypad = kp
+        # self.coord_mapping = [ic(row, col) for (row, col) in self.pin_map]
+        self.coord_mapping = list(range(len(pin_map)))
+
+        self.curr_event = keypad.Event()
+
+    def scan_for_changes(self):
+        '''
+        Scan for key events and return a key report if an event exists.
+
+        The key report is a byte array with contents [row, col, True if pressed else False]
+        '''
+        ev = self.curr_event
+        has_event = self.keypad.events.get_into(ev)
+        if has_event:
+            return ev
+
+
+def keypad_matrix(row_pins, col_pins, direction=DiodeOrientation.COLUMNS):
+    '''
+    Row/Column matrix using the CircuitPython 7 keypad scanner.
+
+    :param row_pins: A sequence of pins used for rows.
+    :param col_pins: A sequence of pins used for columns.
+    :param direction: The diode orientation of the matrix.
+    '''
+    pin_map = [
+        (row, col) for row in range(len(row_pins)) for col in range(len(col_pins))
+    ]
+    kp = keypad.KeyMatrix(row_pins, col_pins, direction == DiodeOrientation.COLUMNS)
+    return NativeKeypadScanner(pin_map, kp)
+
+
+def keys_scanner(pins):
+    '''
+    GPIO-per-key 'matrix' using the native CircuitPython 7 keypad scanner.
+
+    :param pins: An array of arrays of CircuitPython Pin objects, such that pins[r][c] is the pin for row r, column c.
+    '''
+    pin_map = [(row, col) for row in range(len(pins)) for col in range(len(pins[row]))]
+    kp = keypad.Keys(
+        [pins[r][c] for (r, c) in pin_map], value_when_pressed=False, pull=True
+    )
+    return NativeKeypadScanner(pin_map, kp)