1 # How to Customize Your Keyboard's Behavior
3 For a lot of people a custom keyboard is about more than sending button presses to your computer. You want to be able to do things that are more complex than simple button presses and macros. QMK has hooks that allow you to inject code, override functionality, and otherwise customize how your keyboard behaves in different situations.
5 This page does not assume any special knowledge about QMK, but reading [Understanding QMK](understanding_qmk.md) will help you understand what is going on at a more fundamental level.
7 ## A Word on Core vs Keyboards vs Keymap
9 We have structured QMK as a hierarchy:
12 * Keyboard/Revision (`_kb`)
15 Each of the functions described below can be defined with a `_kb()` suffix or a `_user()` suffix. We intend for you to use the `_kb()` suffix at the Keyboard/Revision level, while the `_user()` suffix should be used at the Keymap level.
17 When defining functions at the Keyboard/Revision level it is important that your `_kb()` implementation call `_user()` before executing anything else- otherwise the keymap level function will never be called.
21 By far the most common task is to change the behavior of an existing keycode or to create a new keycode. From a code standpoint the mechanism for each is very similar.
23 ## Defining a New Keycode
25 The first step to creating your own custom keycode(s) is to enumerate them. This means both naming them and assigning a unique number to that keycode. Rather than limit custom keycodes to a fixed range of numbers QMK provides the `SAFE_RANGE` macro. You can use `SAFE_RANGE` when enumerating your custom keycodes to guarantee that you get a unique number.
28 Here is an example of enumerating 2 keycodes. After adding this block to your `keymap.c` you will be able to use `FOO` and `BAR` inside your keymap.
37 ## Programming the Behavior of Any Keycode
39 When you want to override the behavior of an existing key, or define the behavior for a new key, you should use the `process_record_kb()` and `process_record_user()` functions. These are called by QMK during key processing before the actual key event is handled. If these functions return `true` QMK will process the keycodes as usual. That can be handy for extending the functionality of a key rather than replacing it. If these functions return `false` QMK will skip the normal key handling, and it will be up to you to send any key up or down events that are required.
41 These function are called every time a key is pressed or released.
43 ### Example `process_record_user()` Implementation
45 This example does two things. It defines the behavior for a custom keycode called `FOO`, and it supplements our Enter key by playing a tone whenever it is pressed.
48 bool process_record_user(uint16_t keycode, keyrecord_t *record) {
51 if (record->event.pressed) {
52 // Do something when pressed
54 // Do something else when release
56 return false; // Skip all further processing of this key
58 // Play a tone when enter is pressed
59 if (record->event.pressed) {
60 PLAY_NOTE_ARRAY(tone_qwerty);
62 return true; // Let QMK send the enter press/release events
64 return true; // Process all other keycodes normally
69 ### `process_record_*` Function Documentation
71 * Keyboard/Revision: `bool process_record_kb(uint16_t keycode, keyrecord_t *record)`
72 * Keymap: `bool process_record_user(uint16_t keycode, keyrecord_t *record)`
74 The `keycode` argument is whatever is defined in your keymap, eg `MO(1)`, `KC_L`, etc. You should use a `switch...case` block to handle these events.
76 The `record` argument contains information about the actual press:
93 QMK provides methods to read 5 of the LEDs defined in the HID spec:
101 There are two ways to get the lock LED state:
103 * by implementing `bool led_update_kb(led_t led_state)` or `_user(led_t led_state)`; or
104 * by calling `led_t host_keyboard_led_state()`
106 !> `host_keyboard_led_state()` may already reflect a new value before `led_update_user()` is called.
108 Two more deprecated functions exist that provide the LED state as a `uint8_t`:
110 * `uint8_t led_set_kb(uint8_t usb_led)` and `_user(uint8_t usb_led)`
111 * `uint8_t host_keyboard_leds()`
113 ## `led_update_user()`
115 This function will be called when the state of one of those 5 LEDs changes. It receives the LED state as a struct parameter.
117 You must return either `true` or `false` from this function, depending on whether you want to override the keyboard-level implementation.
119 ?> Because the `led_set_*` functions return `void` instead of `bool`, they do not allow for overriding the keyboard LED control, and thus it's recommended to use `led_update_*` instead.
121 ### Example `led_update_kb()` Implementation
124 bool led_update_kb(led_t led_state) {
125 if(led_update_user(led_state)) {
126 if (led_state.num_lock) {
131 if (led_state.caps_lock) {
136 if (led_state.scroll_lock) {
141 if (led_state.compose) {
146 if (led_state.kana) {
156 ### Example `led_update_user()` Implementation
159 bool led_update_user(led_t led_state) {
160 if (led_state.num_lock) {
165 if (led_state.caps_lock) {
170 if (led_state.scroll_lock) {
175 if (led_state.compose) {
180 if (led_state.kana) {
189 ### `led_update_*` Function Documentation
191 * Keyboard/Revision: `bool led_update_kb(led_t led_state)`
192 * Keymap: `bool led_update_user(led_t led_state)`
194 ## `host_keyboard_led_state()`
196 Call this function to get the last received LED state as a `led_t`. This is useful for reading the LED state outside `led_update_*`, e.g. in [`matrix_scan_user()`](#matrix-scanning-code).
198 ## Setting Physical LED State
200 Some keyboard implementations provide convenience methods for setting the state of the physical LEDs.
204 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.
206 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)`.
208 Ergodox boards also define `LED_BRIGHTNESS_LO` for the lowest brightness and `LED_BRIGHTNESS_HI` for the highest brightness (which is the default).
210 # Keyboard Initialization Code
212 There are several steps in the keyboard initialization process. Depending on what you want to do, it will influence which function you should use.
214 These are the three main initialization functions, listed in the order that they're called.
216 * `keyboard_pre_init_*` - Happens before most anything is started. Good for hardware setup that you want running very early.
217 * `matrix_init_*` - Happens midway through the firmware's startup process. Hardware is initialized, but features may not be yet.
218 * `keyboard_post_init_*` - Happens at the end of the firmware's startup process. This is where you'd want to put "customization" code, for the most part.
220 !> For most people, the `keyboard_post_init_user` function is what you want to call. For instance, this is where you want to set up things for RGB Underglow.
222 ## Keyboard Pre Initialization code
224 This runs very early during startup, even before the USB has been started.
226 Shortly after this, the matrix is initialized.
228 For most users, this shouldn't be used, as it's primarily for hardware oriented initialization.
230 However, if you have hardware stuff that you need initialized, this is the best place for it (such as initializing LED pins).
232 ### Example `keyboard_pre_init_user()` Implementation
234 This example, at the keyboard level, sets up B0, B1, B2, B3, and B4 as LED pins.
237 void keyboard_pre_init_user(void) {
238 // Call the keyboard pre init code.
240 // Set our LED pins as output
249 ### `keyboard_pre_init_*` Function Documentation
251 * Keyboard/Revision: `void keyboard_pre_init_kb(void)`
252 * Keymap: `void keyboard_pre_init_user(void)`
254 ## Matrix Initialization Code
256 This is called when the matrix is initialized, and after some of the hardware has been set up, but before many of the features have been initialized.
258 This is useful for setting up stuff that you may need elsewhere, but isn't hardware related nor is dependant on where it's started.
261 ### `matrix_init_*` Function Documentation
263 * Keyboard/Revision: `void matrix_init_kb(void)`
264 * Keymap: `void matrix_init_user(void)`
267 ## Keyboard Post Initialization code
269 This is ran as the very last task in the keyboard initialization process. This is useful if you want to make changes to certain features, as they should be initialized by this point.
272 ### Example `keyboard_post_init_user()` Implementation
274 This example, running after everything else has initialized, sets up the rgb underglow configuration.
277 void keyboard_post_init_user(void) {
278 // Call the post init code.
279 rgblight_enable_noeeprom(); // enables Rgb, without saving settings
280 rgblight_sethsv_noeeprom(180, 255, 255); // sets the color to teal/cyan without saving
281 rgblight_mode_noeeprom(RGBLIGHT_MODE_BREATHING + 3); // sets mode to Fast breathing without saving
285 ### `keyboard_post_init_*` Function Documentation
287 * Keyboard/Revision: `void keyboard_post_init_kb(void)`
288 * Keymap: `void keyboard_post_init_user(void)`
290 # Matrix Scanning Code
292 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.
294 ### Example `matrix_scan_*` Implementation
296 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 Discord](https://discord.gg/Uq7gcHh).
298 ### `matrix_scan_*` Function Documentation
300 * Keyboard/Revision: `void matrix_scan_kb(void)`
301 * Keymap: `void matrix_scan_user(void)`
303 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.
305 You should use this function if you need custom matrix scanning code. It can also be used for custom status output (such as LEDs or a display) or other functionality that you want to trigger regularly even when the user isn't typing.
308 # Keyboard Idling/Wake Code
310 If the board supports it, it can be "idled", by stopping a number of functions. A good example of this is RGB lights or backlights. This can save on power consumption, or may be better behavior for your keyboard.
312 This is controlled by two functions: `suspend_power_down_*` and `suspend_wakeup_init_*`, which are called when the system board is idled and when it wakes up, respectively.
315 ### Example suspend_power_down_user() and suspend_wakeup_init_user() Implementation
319 void suspend_power_down_user(void) {
320 rgb_matrix_set_suspend_state(true);
323 void suspend_wakeup_init_user(void) {
324 rgb_matrix_set_suspend_state(false);
328 ### Keyboard suspend/wake Function Documentation
330 * Keyboard/Revision: `void suspend_power_down_kb(void)` and `void suspend_wakeup_init_user(void)`
331 * Keymap: `void suspend_power_down_kb(void)` and `void suspend_wakeup_init_user(void)`
335 This runs code every time that the layers get changed. This can be useful for layer indication, or custom layer handling.
337 ### Example `layer_state_set_*` Implementation
339 This example shows how to set the [RGB Underglow](feature_rgblight.md) lights based on the layer, using the Planck as an example
342 layer_state_t layer_state_set_user(layer_state_t state) {
343 switch (get_highest_layer(state)) {
345 rgblight_setrgb (0x00, 0x00, 0xFF);
348 rgblight_setrgb (0xFF, 0x00, 0x00);
351 rgblight_setrgb (0x00, 0xFF, 0x00);
354 rgblight_setrgb (0x7A, 0x00, 0xFF);
356 default: // for any other layers, or the default layer
357 rgblight_setrgb (0x00, 0xFF, 0xFF);
363 ### `layer_state_set_*` Function Documentation
365 * Keyboard/Revision: `layer_state_t layer_state_set_kb(layer_state_t state)`
366 * Keymap: `layer_state_t layer_state_set_user(layer_state_t state)`
369 The `state` is the bitmask of the active layers, as explained in the [Keymap Overview](keymap.md#keymap-layer-status)
372 # Persistent Configuration (EEPROM)
374 This allows you to configure persistent settings for your keyboard. These settings are stored in the EEPROM of your controller, and are retained even after power loss. The settings can be read with `eeconfig_read_kb` and `eeconfig_read_user`, and can be written to using `eeconfig_update_kb` and `eeconfig_update_user`. This is useful for features that you want to be able to toggle (like toggling rgb layer indication). Additionally, you can use `eeconfig_init_kb` and `eeconfig_init_user` to set the default values for the EEPROM.
376 The complicated part here, is that there are a bunch of ways that you can store and access data via EEPROM, and there is no "correct" way to do this. However, you only have a DWORD (4 bytes) for each function.
378 Keep in mind that EEPROM has a limited number of writes. While this is very high, it's not the only thing writing to the EEPROM, and if you write too often, you can potentially drastically shorten the life of your MCU.
380 * If you don't understand the example, then you may want to avoid using this feature, as it is rather complicated.
382 ### Example Implementation
384 This is an example of how to add settings, and read and write it. We're using the user keymap for the example here. This is a complex function, and has a lot going on. In fact, it uses a lot of the above functions to work!
387 In your keymap.c file, add this to the top:
392 bool rgb_layer_change :1;
396 user_config_t user_config;
399 This sets up a 32 bit structure that we can store settings with in memory, and write to the EEPROM. Using this removes the need to define variables, since they're defined in this structure. Remember that `bool` (boolean) values use 1 bit, `uint8_t` uses 8 bits, `uint16_t` uses up 16 bits. You can mix and match, but changing the order can cause issues, as it will change the values that are read and written.
401 We're using `rgb_layer_change`, for the `layer_state_set_*` function, and use `keyboard_post_init_user` and `process_record_user` to configure everything.
403 Now, using the `keyboard_post_init_user` code above, you want to add `eeconfig_read_user()` to it, to populate the structure you've just created. And you can then immediately use this structure to control functionality in your keymap. And It should look like:
405 void keyboard_post_init_user(void) {
406 // Call the keymap level matrix init.
408 // Read the user config from EEPROM
409 user_config.raw = eeconfig_read_user();
411 // Set default layer, if enabled
412 if (user_config.rgb_layer_change) {
413 rgblight_enable_noeeprom();
414 rgblight_sethsv_noeeprom_cyan();
415 rgblight_mode_noeeprom(1);
419 The above function will use the EEPROM config immediately after reading it, to set the default layer's RGB color. The "raw" value of it is converted in a usable structure based on the "union" that you created above.
422 layer_state_t layer_state_set_user(layer_state_t state) {
423 switch (get_highest_layer(state)) {
425 if (user_config.rgb_layer_change) { rgblight_sethsv_noeeprom_magenta(); rgblight_mode_noeeprom(1); }
428 if (user_config.rgb_layer_change) { rgblight_sethsv_noeeprom_red(); rgblight_mode_noeeprom(1); }
431 if (user_config.rgb_layer_change) { rgblight_sethsv_noeeprom_green(); rgblight_mode_noeeprom(1); }
434 if (user_config.rgb_layer_change) { rgblight_sethsv_noeeprom_white(); rgblight_mode_noeeprom(1); }
436 default: // for any other layers, or the default layer
437 if (user_config.rgb_layer_change) { rgblight_sethsv_noeeprom_cyan(); rgblight_mode_noeeprom(1); }
443 This will cause the RGB underglow to be changed ONLY if the value was enabled. Now to configure this value, create a new keycode for `process_record_user` called `RGB_LYR`. Additionally, we want to make sure that if you use the normal RGB codes, that it turns off Using the example above, make it look this:
446 bool process_record_user(uint16_t keycode, keyrecord_t *record) {
449 if (record->event.pressed) {
450 // Do something when pressed
452 // Do something else when release
454 return false; // Skip all further processing of this key
456 // Play a tone when enter is pressed
457 if (record->event.pressed) {
458 PLAY_NOTE_ARRAY(tone_qwerty);
460 return true; // Let QMK send the enter press/release events
461 case RGB_LYR: // This allows me to use underglow as layer indication, or as normal
462 if (record->event.pressed) {
463 user_config.rgb_layer_change ^= 1; // Toggles the status
464 eeconfig_update_user(user_config.raw); // Writes the new status to EEPROM
465 if (user_config.rgb_layer_change) { // if layer state indication is enabled,
466 layer_state_set(layer_state); // then immediately update the layer color
470 case RGB_MODE_FORWARD ... RGB_MODE_GRADIENT: // For any of the RGB codes (see quantum_keycodes.h, L400 for reference)
471 if (record->event.pressed) { //This disables layer indication, as it's assumed that if you're changing this ... you want that disabled
472 if (user_config.rgb_layer_change) { // only if this is enabled
473 user_config.rgb_layer_change = false; // disable it, and
474 eeconfig_update_user(user_config.raw); // write the setings to EEPROM
479 return true; // Process all other keycodes normally
483 And lastly, you want to add the `eeconfig_init_user` function, so that when the EEPROM is reset, you can specify default values, and even custom actions. To force an EEPROM reset, use the `EEP_RST` keycode or [Bootmagic](feature_bootmagic.md) functionallity. For example, if you want to set rgb layer indication by default, and save the default valued.
486 void eeconfig_init_user(void) { // EEPROM is getting reset!
488 user_config.rgb_layer_change = true; // We want this enabled by default
489 eeconfig_update_user(user_config.raw); // Write default value to EEPROM now
491 // use the non noeeprom versions, to write these values to EEPROM too
492 rgblight_enable(); // Enable RGB by default
493 rgblight_sethsv_cyan(); // Set it to CYAN by default
494 rgblight_mode(1); // set to solid by default
498 And you're done. The RGB layer indication will only work if you want it to. And it will be saved, even after unplugging the board. And if you use any of the RGB codes, it will disable the layer indication, so that it stays on the mode and color that you set it to.
500 ### 'EECONFIG' Function Documentation
502 * Keyboard/Revision: `void eeconfig_init_kb(void)`, `uint32_t eeconfig_read_kb(void)` and `void eeconfig_update_kb(uint32_t val)`
503 * Keymap: `void eeconfig_init_user(void)`, `uint32_t eeconfig_read_user(void)` and `void eeconfig_update_user(uint32_t val)`
505 The `val` is the value of the data that you want to write to EEPROM. And the `eeconfig_read_*` function return a 32 bit (DWORD) value from the EEPROM.
507 # Custom Tapping Term
509 By default, the tapping term is defined globally, and is not configurable by key. For most users, this is perfectly fine. But in come cases, dual function keys would be greatly improved by different timeouts than `LT` keys, or because some keys may be easier to hold than others. Instead of using custom key codes for each, this allows for per key configurable `TAPPING_TERM`.
511 To enable this functionality, you need to add `#define TAPPING_TERM_PER_KEY` to your `config.h`, first.
514 ## Example `get_tapping_term` Implementation
516 To change the `TAPPING TERM` based on the keycode, you'd want to add something like the following to your `keymap.c` file:
519 uint16_t get_tapping_term(uint16_t keycode) {
522 return TAPPING_TERM + 1250;
531 ### `get_tapping_term` Function Documentation
533 Unlike many of the other functions here, there isn't a need (or even reason) to have a quantum or keyboard level function. Only a user level function is useful here, so no need to mark it as such.