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diff --git a/docs/features/led_indicators.md b/docs/features/led_indicators.md new file mode 100644 index 0000000000..8435c69a55 --- /dev/null +++ b/docs/features/led_indicators.md @@ -0,0 +1,127 @@ +# LED Indicators + +::: tip +LED indicators on split keyboards will require state information synced to the slave half (e.g. `#define SPLIT_LED_STATE_ENABLE`). See [data sync options](split_keyboard#data-sync-options) for more details. +::: + +QMK provides methods to read 5 of the LEDs defined in the HID spec: + +* Num Lock +* Caps Lock +* Scroll Lock +* Compose +* Kana + +There are three ways to get the lock LED state: +* Configuration options in `config.h` +* Implement `led_update_*` function +* Call `led_t host_keyboard_led_state()` + +::: warning +The `host_keyboard_led_state()` may reflect an updated state before `led_update_user()` is called. +::: + +Two deprecated functions that provide the LED state as `uint8_t`: + +* `uint8_t led_set_user(uint8_t usb_led)` +* `uint8_t host_keyboard_leds()` + +## Configuration Options + +To configure the indicators, `#define` these in your `config.h`: + +|Define |Default |Description | +|---------------------|-------------|-------------------------------------------| +|`LED_NUM_LOCK_PIN` |*Not defined*|The pin that controls the `Num Lock` LED | +|`LED_CAPS_LOCK_PIN` |*Not defined*|The pin that controls the `Caps Lock` LED | +|`LED_SCROLL_LOCK_PIN`|*Not defined*|The pin that controls the `Scroll Lock` LED| +|`LED_COMPOSE_PIN` |*Not defined*|The pin that controls the `Compose` LED | +|`LED_KANA_PIN` |*Not defined*|The pin that controls the `Kana` LED | +|`LED_PIN_ON_STATE` |`1` |The state of the indicator pins when the LED is "on" - `1` for high, `0` for low| + +Unless you are designing your own keyboard, you generally should not need to change the above config options. + +## LED update function + +When the configuration options do not provide enough flexibility, the following callbacks allow custom control of the LED behavior. These functions will be called when one of those 5 LEDs changes state: + +* Keyboard/revision: `bool led_update_kb(led_t led_state)` +* Keymap: `bool led_update_user(led_t led_state)` + +Both receives LED state as a struct parameter. Returning `true` in `led_update_user()` will allow the keyboard level code in `led_update_kb()` to run as well. Returning `false` will override the keyboard level code, depending on how the keyboard level function is set up. + +::: tip +This boolean return type of `led_update_user` allows for overriding keyboard LED controls, and is thus recommended over the void `led_set_user` function. +::: + +### Example of keyboard LED update implementation + +This is a template indicator function that can be implemented on keyboard level code: + +```c +bool led_update_kb(led_t led_state) { + bool res = led_update_user(led_state); + if(res) { + // gpio_write_pin sets the pin high for 1 and low for 0. + // In this example the pins are inverted, setting + // it low/0 turns it on, and high/1 turns the LED off. + // This behavior depends on whether the LED is between the pin + // and VCC or the pin and GND. + gpio_write_pin(B0, !led_state.num_lock); + gpio_write_pin(B1, !led_state.caps_lock); + gpio_write_pin(B2, !led_state.scroll_lock); + gpio_write_pin(B3, !led_state.compose); + gpio_write_pin(B4, !led_state.kana); + } + return res; +} +``` + +### Example of user LED update implementation + +This is an incomplete example will play a sound if Caps Lock is turned on or off. It returns `true` to allow keyboard LED function to maintain their state. + +```c +#ifdef AUDIO_ENABLE + float caps_on[][2] = SONG(CAPS_LOCK_ON_SOUND); + float caps_off[][2] = SONG(CAPS_LOCK_OFF_SOUND); +#endif + +bool led_update_user(led_t led_state) { + #ifdef AUDIO_ENABLE + static uint8_t caps_state = 0; + if (caps_state != led_state.caps_lock) { + led_state.caps_lock ? PLAY_SONG(caps_on) : PLAY_SONG(caps_off); + caps_state = led_state.caps_lock; + } + #endif + return true; +} +``` + +## Host keyboard LED state + +The `host_keyboard_led_state()` function will report the LED state returned from the host computer as `led_t`. This is useful for reading the LED state outside `led_update_*`. For example, you can get the boolean state of Caps Lock from the host with: + +```c +bool caps = host_keyboard_led_state().caps_lock; +``` + +## `led_update_ports()` + +This function writes the LED state to the actual hardware. Call it manually +from your `led_update_*()` callbacks to modify the handling of the standard +keyboard LEDs. +For example when repurposing a standard LED indicator as layer indicator. + +## Setting Physical LED State + +Some keyboard implementations provide convenient methods for setting the state of the physical LEDs. + +### Ergodox Boards + +The Ergodox implementations provide `ergodox_right_led_1`/`2`/`3_on`/`off()` to turn individual LEDs on or off, as well as `ergodox_right_led_on`/`off(uint8_t led)` to turn them on or off by their index. + +In addition, it is possible to specify the brightness level of all LEDs with `ergodox_led_all_set(uint8_t n)`; of individual LEDs with `ergodox_right_led_1`/`2`/`3_set(uint8_t n)`; or by index with `ergodox_right_led_set(uint8_t led, uint8_t n)`. + +Ergodox boards also define `LED_BRIGHTNESS_LO` for the lowest brightness and `LED_BRIGHTNESS_HI` for the highest brightness (which is the default). |