This feature allows you to use LED matrices driven by external drivers. It hooks into the backlight system so you can use the same keycodes as backlighting to control it.
If you want to use RGB LED's you should use the [RGB Matrix Subsystem](feature_rgb_matrix.md) instead.
You can use between 1 and 4 IS31FL3731 IC's. Do not specify `LED_DRIVER_ADDR_<N>` defines for IC's that are not present on your keyboard. You can define the following items in `config.h`:
!> Note the parentheses, this is so when `LED_DRIVER_LED_TOTAL` is used in code and expanded, the values are added together before any additional math is applied to them. As an example, `rand() % (LED_DRIVER_1_LED_TOTAL + LED_DRIVER_2_LED_TOTAL)` will give very different results than `rand() % LED_DRIVER_1_LED_TOTAL + LED_DRIVER_2_LED_TOTAL`.
Where `Cx_y` is the location of the LED in the matrix defined by [the datasheet](https://www.issi.com/WW/pdf/31FL3731.pdf) and the header file `drivers/issi/is31fl3731-simple.h`. The `driver` is the index of the driver you defined in your `config.h` (`0`, `1`, `2`, or `3` ).
From this point forward the configuration is the same for all the drivers. The `led_config_t` struct provides a key electrical matrix to led index lookup table, what the physical position of each LED is on the board, and what type of key or usage the LED if the LED represents. Here is a brief example:
The first part, `// Key Matrix to LED Index`, tells the system what key this LED represents by using the key's electrical matrix row & col. The second part, `// LED Index to Physical Position` represents the LED's physical `{ x, y }` position on the keyboard. The default expected range of values for `{ x, y }` is the inclusive range `{ 0..224, 0..64 }`. This default expected range is due to effects that calculate the center of the keyboard for their animations. The easiest way to calculate these positions is imagine your keyboard is a grid, and the top left of the keyboard represents `{ x, y }` coordinate `{ 0, 0 }` and the bottom right of your keyboard represents `{ 224, 64 }`. Using this as a basis, you can use the following formula to calculate the physical position:
```c
x = 224 / (NUMBER_OF_COLS - 1) * COL_POSITION
y = 64 / (NUMBER_OF_ROWS - 1) * ROW_POSITION
```
Where NUMBER_OF_COLS, NUMBER_OF_ROWS, COL_POSITION, & ROW_POSITION are all based on the physical layout of your keyboard, not the electrical layout.
As mentioned earlier, the center of the keyboard by default is expected to be `{ 112, 32 }`, but this can be changed if you want to more accurately calculate the LED's physical `{ x, y }` positions. Keyboard designers can implement `#define LED_MATRIX_CENTER { 112, 32 }` in their config.h file with the new center point of the keyboard, or where they want it to be allowing more possibilities for the `{ x, y }` values. Do note that the maximum value for x or y is 255, and the recommended maximum is 224 as this gives animations runoff room before they reset.
`// LED Index to Flag` is a bitmask, whether or not a certain LEDs is of a certain type. It is recommended that LEDs are set to only 1 type.
## Custom LED Matrix Effects :id=custom-led-matrix-effects
By setting `LED_MATRIX_CUSTOM_USER` (and/or `LED_MATRIX_CUSTOM_KB`) in `rules.mk`, new effects can be defined directly from userspace, without having to edit any QMK core files.
To declare new effects, create a new `led_matrix_user/kb.inc` that looks something like this:
`led_matrix_user.inc` should go in the root of the keymap directory.
`led_matrix_kb.inc` should go in the root of the keyboard directory.
To use custom effects in your code, simply prepend `LED_MATRIX_CUSTOM_` to the effect name specified in `LED_MATRIX_EFFECT()`. For example, an effect declared as `LED_MATRIX_EFFECT(my_cool_effect)` would be referenced with:
#define LED_DISABLE_TIMEOUT 0 // number of milliseconds to wait until led automatically turns off
#define LED_DISABLE_AFTER_TIMEOUT 0 // OBSOLETE: number of ticks to wait until disabling effects
#define LED_DISABLE_WHEN_USB_SUSPENDED false // turn off effects when suspended
#define LED_MATRIX_LED_PROCESS_LIMIT (DRIVER_LED_TOTAL + 4) / 5 // limits the number of LEDs to process in an animation per task run (increases keyboard responsiveness)
#define LED_MATRIX_LED_FLUSH_LIMIT 16 // limits in milliseconds how frequently an animation will update the LEDs. 16 (16ms) is equivalent to limiting to 60fps (increases keyboard responsiveness)
#define LED_MATRIX_MAXIMUM_BRIGHTNESS 255 // limits maximum brightness of LEDs
#define LED_MATRIX_STARTUP_MODE LED_MATRIX_SOLID // Sets the default mode, if none has been set
#define LED_MATRIX_STARTUP_VAL LED_MATRIX_MAXIMUM_BRIGHTNESS // Sets the default brightness value, if none has been set
#define LED_MATRIX_STARTUP_SPD 127 // Sets the default animation speed, if none has been set
#define LED_MATRIX_SPLIT { X, Y } // (Optional) For split keyboards, the number of LEDs connected on each half. X = left, Y = Right.
// If LED_MATRIX_KEYPRESSES or LED_MATRIX_KEYRELEASES is enabled, you also will want to enable SPLIT_TRANSPORT_MIRROR
```
## EEPROM storage :id=eeprom-storage
The EEPROM for it is currently shared with the RGB Matrix system (it's generally assumed only one feature would be used at a time), but could be configured to use its own 32bit address with:
|`led_matrix_set_value_all(v)` |Set all of the LEDs to the given value, where `v` is between 0 and 255 (not written to EEPROM) |
|`led_matrix_set_value(index, v)` |Set a single LED to the given value, where `v` is between 0 and 255, and `index` is between 0 and `DRIVER_LED_TOTAL` (not written to EEPROM) |
|`led_matrix_mode(mode)` |Set the mode, if LED animations are enabled |
|`led_matrix_mode_noeeprom(mode)` |Set the mode, if LED animations are enabled (not written to EEPROM) |
|`led_matrix_step()` |Change the mode to the next LED animation in the list of enabled LED animations |
|`led_matrix_step_noeeprom()` |Change the mode to the next LED animation in the list of enabled LED animations (not written to EEPROM) |
|`led_matrix_step_reverse()` |Change the mode to the previous LED animation in the list of enabled LED animations |
|`led_matrix_step_reverse_noeeprom()` |Change the mode to the previous LED animation in the list of enabled LED animations (not written to EEPROM) |
|`led_matrix_increase_speed()` |Increase the speed of the animations |
|`led_matrix_increase_speed_noeeprom()` |Increase the speed of the animations (not written to EEPROM) |
|`led_matrix_decrease_speed()` |Decrease the speed of the animations |
|`led_matrix_decrease_speed_noeeprom()` |Decrease the speed of the animations (not written to EEPROM) |
|`led_matrix_set_speed(speed)` |Set the speed of the animations to the given value where `speed` is between 0 and 255 |
|`led_matrix_set_speed_noeeprom(speed)` |Set the speed of the animations to the given value where `speed` is between 0 and 255 (not written to EEPROM) |
If you want to set custom indicators, such as an LED for Caps Lock, or layer indication, you can use the `led_matrix_indicators_kb` or `led_matrix_indicators_user` function for that:
In addition, there are the advanced indicator functions. These are aimed at those with heavily customized displays, where rendering every LED per cycle is expensive. This includes a special macro to help make this easier to use: `LED_MATRIX_INDICATOR_SET_VALUE(i, v)`.
