Resolves #56 by moving kmk.common.* up a level to kmk.*

kmk/matrix.py

@@ -0,0 +1,57 @@
+import digitalio
+
+from kmk.consts import DiodeOrientation
+from kmk.event_defs import matrix_changed
+
+
+class MatrixScanner:
+    def __init__(self, cols, rows, diode_orientation=DiodeOrientation.COLUMNS):
+        # A pin cannot be both a row and column, detect this by combining the
+        # two tuples into a set and validating that the length did not drop
+        #
+        # repr() hackery is because CircuitPython Pin objects are not hashable
+        unique_pins = {repr(c) for c in cols} | {repr(r) for r in rows}
+        if len(unique_pins) != len(cols) + len(rows):
+            raise ValueError('Cannot use a pin as both a column and row')
+
+        self.cols = cols
+        self.rows = rows
+        self.diode_orientation = diode_orientation
+        self.last_pressed_len = 0
+
+        if self.diode_orientation == DiodeOrientation.COLUMNS:
+            self.outputs = self.cols
+            self.inputs = self.rows
+        elif self.diode_orientation == DiodeOrientation.ROWS:
+            self.outputs = self.rows
+            self.inputs = self.cols
+        else:
+            raise ValueError('Invalid DiodeOrientation: {}'.format(
+                self.diode_orientation,
+            ))
+
+        for pin in self.outputs:
+            pin.switch_to_output()
+
+        for pin in self.inputs:
+            pin.switch_to_input(pull=digitalio.Pull.DOWN)
+
+    def scan_for_pressed(self):
+        pressed = []
+
+        for oidx, opin in enumerate(self.outputs):
+            opin.value(True)
+
+            for iidx, ipin in enumerate(self.inputs):
+                if ipin.value():
+                    pressed.append(
+                        (oidx, iidx) if self.diode_orientation == DiodeOrientation.ROWS else (iidx, oidx)  # noqa
+                    )
+
+            opin.value(False)
+
+        if len(pressed) != self.last_pressed_len:
+            self.last_pressed_len = len(pressed)
+            return matrix_changed(pressed)
+
+        return None  # The default, but for explicitness