+
+### `led_set_*` Function Documentation
+
+* Keyboard/Revision: `void led_set_kb(uint8_t usb_led)`
+* Keymap: `void led_set_user(uint8_t usb_led)`
+
+# Matrix Initialization Code
+
+Before a keyboard can be used the hardware must be initialized. QMK handles initialization of the keyboard matrix itself, but if you have other hardware like LED's or i²c controllers you will need to set up that hardware before it can be used.
+
+### Example `matrix_init_user()` Implementation
+
+This example, at the keyboard level, sets up B1, B2, and B3 as LED pins.
+
+```
+void matrix_init_user(void) {
+ // Call the keymap level matrix init.
+
+ // Set our LED pins as output
+ DDRB |= (1<<1);
+ DDRB |= (1<<2);
+ DDRB |= (1<<3);
+}
+```
+
+### `matrix_init_*` Function Documentation
+
+* Keyboard/Revision: `void matrix_init_kb(void)`
+* Keymap: `void matrix_init_user(void)`
+
+# Matrix Scanning Code
+
+Whenever possible you should customize your keyboard by using `process_record_*()` and hooking into events that way, to ensure that your code does not have a negative performance impact on your keyboard. However, in rare cases it is necessary to hook into the matrix scanning. Be extremely careful with the performance of code in these functions, as it will be called at least 10 times per second.
+
+### Example `matrix_scan_*` Implementation
+
+This example has been deliberately omitted. You should understand enough about QMK internals to write this without an example before hooking into such a performance sensitive area. If you need help please [open an issue](https://github.com/qmk/qmk_firmware/issues/new) or [chat with us on gitter](https://gitter.im/qmk/qmk_firmware).
+
+### `matrix_scan_*` Function Documentation
+
+* Keyboard/Revision: `void matrix_scan_kb(void)`
+* Keymap: `void matrix_scan_user(void)`
+
+This function gets called at every matrix scan, which is basically as often as the MCU can handle. Be careful what you put here, as it will get run a lot.
+
+You should use this function if you need custom matrix scanning code. It can also be used for custom status output (such as LED's or a display) or other functionality that you want to trigger regularly even when the user isn't typing.
+
+
+# Layer Change Code
+
+Thir runs code every time that the layers get changed. This can be useful for layer indication, or custom layer handling.
+
+### Example `layer_state_set_*` Implementation
+
+This example shows how to set the [RGB Underglow](feature_rgblight.md) lights based on the layer, using the Planck as an example
+
+```
+uint32_t layer_state_set_user(uint32_t state) {
+ switch (biton32(state)) {
+ case _RAISE:
+ rgblight_setrgb (0x00, 0x00, 0xFF);
+ break;
+ case _LOWER:
+ rgblight_setrgb (0xFF, 0x00, 0x00);
+ break;
+ case _PLOVER:
+ rgblight_setrgb (0x00, 0xFF, 0x00);
+ break;
+ case _ADJUST:
+ rgblight_setrgb (0x7A, 0x00, 0xFF);
+ break;
+ default: // for any other layers, or the default layer
+ rgblight_setrgb (0x00, 0xFF, 0xFF);
+ break;
+ }
+ return state;
+}
+```
+### `layer_state_set_*` Function Documentation
+
+* Keyboard/Revision: `void uint32_t layer_state_set_kb(uint32_t state)`
+* Keymap: `uint32_t layer_state_set_user(uint32_t state)`
+
+The `state` is the bitmask of the active layers, as explained in the [Keymap Overview](keymap.md#keymap-layer-status)