implement support for multiple scanners at once

fixup

kmk/scanners/__init__.py

@@ -22,7 +22,12 @@ class Scanner:
     Base class for scanners.
     '''
 
-    coord_mapping = None
+    # for split keyboards, the offset value will be assigned in Split module
+    offset = 0
+
+    @property
+    def coord_mapping(self):
+        return tuple(range(self.offset, self.offset + self.key_count))
 
     @property
     def key_count(self):
@@ -34,4 +39,4 @@ class Scanner:
 
         The key report is a byte array with contents [row, col, True if pressed else False]
         '''
-        pass
+        raise NotImplementedError

kmk/scanners/digitalio.py

@@ -78,7 +78,6 @@ class MatrixScanner(Scanner):
             self.rollover_cols_every_rows = self.len_rows
 
         self._key_count = self.len_cols * self.len_rows
-        self.coord_mapping = tuple(range(self.key_count))
         self.state = bytearray(self.key_count)
 
     @property

kmk/scanners/keypad.py

@@ -12,9 +12,6 @@ class KeypadScanner(Scanner):
     '''
 
     def __init__(self):
-        # for split keyboards, the offset value will be assigned in Split module
-        self.offset = 0
-        self.coord_mapping = tuple(range(self.key_count))
         self.curr_event = keypad.Event()
 
     @property