1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
|
# How to Customize Your Keyboard's Behavior
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.
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.
## A Word on Core vs Keyboards vs Keymap
We have structured QMK as a hierarchy:
* Core (`_quantum`)
* Keyboard/Revision (`_kb`)
* Keymap (`_user`)
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.
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.
# Custom Keycodes
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.
## Defining a New Keycode
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.
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.
```c
enum my_keycodes {
FOO = SAFE_RANGE,
BAR
};
```
## Programming the Behavior of Any Keycode
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.
These function are called every time a key is pressed or released.
### Example `process_record_user()` Implementation
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.
```c
bool process_record_user(uint16_t keycode, keyrecord_t *record) {
switch (keycode) {
case FOO:
if (record->event.pressed) {
// Do something when pressed
} else {
// Do something else when release
}
return false; // Skip all further processing of this key
case KC_ENTER:
// Play a tone when enter is pressed
if (record->event.pressed) {
PLAY_NOTE_ARRAY(tone_qwerty);
}
return true; // Let QMK send the enter press/release events
default:
return true; // Process all other keycodes normally
}
}
```
### `process_record_*` Function Documentation
* Keyboard/Revision: `bool process_record_kb(uint16_t keycode, keyrecord_t *record)`
* Keymap: `bool process_record_user(uint16_t keycode, keyrecord_t *record)`
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.
The `record` argument contains information about the actual press:
```c
keyrecord_t record {
keyevent_t event {
keypos_t key {
uint8_t col
uint8_t row
}
bool pressed
uint16_t time
}
}
```
# LED Control
QMK provides methods to read 5 of the LEDs defined in the HID spec:
* Num Lock
* Caps Lock
* Scroll Lock
* Compose
* Kana
There are two ways to get the lock LED state:
* by implementing `bool led_update_kb(led_t led_state)` or `_user(led_t led_state)`; or
* by calling `led_t host_keyboard_led_state()`
!> `host_keyboard_led_state()` may already reflect a new value before `led_update_user()` is called.
Two more deprecated functions exist that provide the LED state as a `uint8_t`:
* `uint8_t led_set_kb(uint8_t usb_led)` and `_user(uint8_t usb_led)`
* `uint8_t host_keyboard_leds()`
## `led_update_user()`
This function will be called when the state of one of those 5 LEDs changes. It receives the LED state as a struct parameter.
By convention, return `true` from `led_update_user()` to get the `led_update_kb()` hook to run its code, and
return `false` when you would prefer not to run the code in `led_update_kb()`.
Some examples include:
- overriding the LEDs to use them for something else like layer indication
- return `false` because you do not want the `_kb()` function to run, as it would override your layer behavior.
- play a sound when an LED turns on or off.
- return `true` because you want the `_kb` function to run, and this is in addition to the default LED behavior.
?> 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.
### Example `led_update_kb()` Implementation
```c
bool led_update_kb(led_t led_state) {
bool res = led_update_user(led_state);
if(res) {
// writePin 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.
writePin(B0, !led_state.num_lock);
writePin(B1, !led_state.caps_lock);
writePin(B2, !led_state.scroll_lock);
writePin(B3, !led_state.compose);
|
