# Scanners The default key scanner in KMK assumes a garden variety switch matrix, with one diode per switch to prevent ghosting. This doesn't cover all hardware designs though. With macro pads, for example, it is very common to not have a matrix topology at all. Boards like this aren't compatible with the default matrix scanner, so you will need to swap it out with an alternative scanner. ## Keypad Scanners The scanners in `kmk.scanners.keypad` wrap the `keypad` module that ships with CircuitPython and support the some configuration and tuning options as their upstream. You can find out more in the (CircuitPython documentation)[https://docs.circuitpython.org/en/latest/shared-bindings/keypad/index.html]. ### keypad MatrixScanner This is the default scanner used by KMK. It uses the CircuitPython builtin `keypad.KeyMatrix`. ```python from kmk.scanners.keypad import MatrixScanner class MyKeyboard(KMKKeyboard): def __init__(self): # create and register the scanner self.matrix = MatrixScanner( # required arguments: column_pins=self.col_pins, row_pins=self.row_pins, # optional arguments with defaults: columns_to_anodes=DiodeOrientation.COL2ROW, interval=0.02, max_events=64 ) ``` ### keypad KeysScanner The `keypad.Keys` scanner treats individual GPIO pins as discrete keys. To use this scanner, provide a sequence of pins that describes the layout of your board then include it in the initialization sequence of your keyboard class. ```python import board from kmk.kmk_keyboard import KMKKeyboard from kmk.scanners.keypad import KeysScanner # GPIO to key mapping - each line is a new row. _KEY_CFG = [ board.SW3, board.SW7, board.SW11, board.SW15, board.SW2, board.SW6, board.SW10, board.SW14, board.SW1, board.SW5, board.SW9, board.SW13, board.SW0, board.SW4, board.SW8, board.SW12, ] # Keyboard implementation class class MyKeyboard(KMKKeyboard): def __init__(self): # create and register the scanner self.matrix = MatrixScanner( # require argument: pins=_KEY_CFG, # optional arguments with defaults: value_when_pressed=False, pull=True, interval=0.02, max_events=64 ) ``` ### keypad ShiftRegisterKeys This scanner can read keys attached to a parallel-in serial-out shift register like the 74HC165 or CD4021. Note that you may chain shift registers to load in as many values as you need. ```python from kmk.scanners.keypad import ShiftRegisterKeys class MyKeyboard(KMKKeyboard): def __init__(self): # create and register the scanner self.matrix = ShiftRegisterKeys( # require arguments: clock=board.GP0, data=board.GP1, latch=board.GP2, key_count=8, # optional arguments with defaults: value_to_latch=True, # 74HC165: True, CD4021: False value_when_pressed=False, interval=0.02, max_events=64 ) ``` ## Digitalio Scanners ### digitalio MatrixScanner The digitalio Matrix can scan over, as the name implies, `digitalio.DigitalInOut` objects. That is especially useful if a matrix is build with IO-expanders. ```python from kmk.scanners.digitalio import MatrixScanner class MyKeyboard(KMKKeyboard): def __init__(self): # create and register the scanner self.matrix = MatrixScanner( cols=self.col_pins, rows=self.row_pins, diode_orientation=self.diode_orientation, rollover_cols_every_rows=None, # optional ) ``` ## Rotary Encoder Scanners ### RotaryioEncoder Matrix events from a quadrature ("rotary") encoder? ```python from kmk.scanners.encoder import RotaryioEncoder class MyKeyboard(KMKKeyboard): def __init__(self): # create and register the scanner self.matrix = RotaryioEncoder( pin_a=board.GP0, pin_b=board.GP1, # optional divisor=4, ) ``` ## `Scanner` base class If you require a different type of scanner, you can create your own by providing a subclass of `Scanner`. This is a very simple interface, it only contains a single method, `scan_for_changes(self)` which returns a key report if one exists, or `None` otherwise. ## Advanced Configuration ### Multiple Scanners Sometimes a single scanner doesn't cover all hardware configurations. For example: The bulk of the keyboard may be scanned with a matrix scanner, but a couple of additional keys are directly connected to GPIOs. In that case KMK allows you to define multiple scanners. The `KMKKeyboard.matrix` attribute can either be assigned a single scanner, or a list of scanners. KMK assumes that successive scanner keys are consecutive, and populates `KMKKeyboard.coord_mapping` accordingly; for convenience you may have to supply a `coord_mapping` that resembles your physical layout more closely. Example: ```python class MyKeyboard(KMKKeyboard): self.matrix = [ MatrixScanner(...), KeysScanner(...), # etc... ] ``` #### Multiple Scanners coord_mapping and keymap changes To add more scanners you need to add onto your your " coord_mapping " Example below. Before: ```python coord_mapping = [ 0, 1, 2, 3, 4, 5, 35, 34, 33, 32, 31, 30, 6, 7, 8, 9, 10, 11, 41, 40, 39, 38, 37, 36, 12, 13, 14, 15, 16, 17, 47, 46, 45, 44, 43, 42, 18, 19, 20, 21, 22, 23, 29, 59, 53, 52, 51, 50, 49, 48, 25, 26, 27, 28, 58, 57, 56, 55, ] ``` After: ```python coord_mapping = [ 0, 1, 2, 3, 4, 5, 37, 36, 35, 34, 33, 32, 6, 7, 8, 9, 10, 11, 43, 42, 41, 40, 39, 38, 12, 13, 14, 15, 16, 17, 49, 48, 47, 46, 45, 44, 18, 19, 20, 21, 22, 23, 29, 61, 55, 54, 53, 52, 51, 50, 25, 26, 27, 28, 60, 59, 58, 57, 30, 31, 62, 63 ] ``` This is as complicated as it can be. Split with "RotaryioEncoder" and "MatrixScanner". You will see that the top left side used to count up to 29 and the right side started at 30. With the encoder module added on the left side has 2 more keys so it now counts up to 31 and the right side starts its count at 32 and continues to 63. 30,31,62 and 63 are all for encoders. You will see that all of the encoders are at the end of the array, this means that we need to add 4 more key codes to the end of our `keymap` in `main.py`