# Configuring KMK

KMK is configured through a rather large plain-old-Python class called
`KMKKeyboard`. Subclasses of this configuration exist which pre-fill defaults
for various known keyboards (for example, many QMK, TMK, or ZMK keyboards 
are supported with a nice!nano, or through our ItsyBitsy to ProMicro pinout adapter. 
This class is the main interface between end users and the inner workings of KMK. 
Let's dive in!

- Edit or create a file called `main.py` on your `CIRCUITPY` drive. You can also
  keep this file on your computer (perhaps under `user_keymaps` - please feel
  free to submit a pull request with your layout definitions!) and copy it over
  (either manually or, if you're adept with developer tooling and/or a command
  line, [our
  Makefile](https://github.com/KMKfw/kmk_firmware/blob/master/docs/flashing.md)).
  It's definitely recommended to keep a backup of your configuration somewhere
  that isn't the microcontroller itself - MCUs die, CircuitPython may run into
  corruption bugs, or you might just have bad luck and delete the wrong file
  some day.

- Assign a `KMKKeyboard` instance to a variable (ex. `keyboard = KMKKeyboard()` - note
  the parentheses)

- Make sure this `KMKKeyboard` instance is actually run at the end of the file with
  a block such as the following:

```python
if __name__ == '__main__':
    keyboard.go()
```

- Assign pins and your diode orientation (only necessary on handwire keyboards),
  for example:

```python
import board

from kmk.matrix import DiodeOrientation

col_pins = (board.SCK, board.MOSI, board.MISO, board.RX, board.TX, board.D4)
row_pins = (board.D10, board.D11, board.D12, board.D13, board.D9, board.D6, board.D5, board.SCL)
rollover_cols_every_rows = 4
diode_orientation = DiodeOrientation.COL2ROW
```

The pins should be based on whatever CircuitPython calls pins on your particular
board. You can find these in the REPL on your CircuitPython device:

```python
import board
print(dir(board))
```

> Note: `rollover_cols_every_rows` is only supported with
> `DiodeOrientation.COLUMNS`/`DiodeOrientation.COL2ROW`, not `DiodeOrientation.ROWS`/`DiodeOrientation.ROW2COL`. It is used for boards
> such as the Planck Rev6 which reuse column pins to simulate a 4x12 matrix in
> the form of an 8x6 matrix

- Import the global list of key definitions with `from kmk.keys import KC`. You
  can either print this out in the REPL as we did with `board` above, or simply
  look at [our Key
  documentation](https://github.com/KMKfw/kmk_firmware/blob/master/docs/keycodes.md).
  We've tried to keep that listing reasonably up to date, but if it feels like
  something is missing, you may need to read through `kmk/keys.py` (and then
  open a ticket to tell us our docs are out of date, or open a PR and fix the
  docs yourself!)

- Define a keymap, which is, in Python terms, a List of Lists of `Key` objects.
  A very simple keymap, for a keyboard with just two physical keys on a single
  layer, may look like this:

```python
keyboard.keymap = [[KC.A, KC.B]]
```

You can further define a bunch of other stuff:

- `keyboard.debug_enabled` which will spew a ton of debugging information to the serial
  console. This is very rarely needed, but can provide very valuable information
  if you need to open an issue.

- `keyboard.tap_time` which defines how long `KC.TT` and `KC.LT` will wait before
  considering a key "held" (see `layers.md`)