* `USB_LED_COMPOSE`
* `USB_LED_KANA`
-### Example `led_set_kb()` Implementation
+### Example `led_set_user()` Implementation
```
-void led_set_kb(uint8_t usb_led) {
+void led_set_user(uint8_t usb_led) {
if (usb_led & (1<<USB_LED_NUM_LOCK)) {
PORTB |= (1<<0);
} else {
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_kb()` Implementation
+### Example `matrix_init_user()` Implementation
This example, at the keyboard level, sets up B1, B2, and B3 as LED pins.
```
-void matrix_init_kb(void) {
+void matrix_init_user(void) {
// Call the keymap level matrix init.
- matrix_init_user();
// Set our LED pins as output
DDRB |= (1<<1);
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)