Struggling with QMK modifier keys

Question

I'm getting this error when I try to use modifier keys on my rotary encoder like so:

bool encoder_update_user(uint8_t index, bool clockwise) {
    if (index == 0) { /* First encoder */
        if (clockwise) {
            tap_code(QK_LCTL | KC_F24);
        } else {
            tap_code(QK_LCTL | KC_F23);
        }
    } 
    return false;
}

This is the error:

Compiling: keyboards/planck/keymaps/dawz/keymap.c                                                  keyboards/planck/keymaps/dawz/keymap.c: In function 'encoder_update_user':
keyboards/planck/keymaps/dawz/keymap.c:68:22: error: unsigned conversion from 'int' to 'uint8_t' {aka 'unsigned char'} changes value from '371' to '115' [-Werror=overflow]
   68 |             tap_code(QK_LCTL | KC_F24);
      |                      ^~~~~~~~~~~~~~~~
keyboards/planck/keymaps/dawz/keymap.c:70:22: error: unsigned conversion from 'int' to 'uint8_t' {aka 'unsigned char'} changes value from '370' to '114' [-Werror=overflow]
   70 |             tap_code(QK_LCTL | KC_F23);
      |                      ^~~~~~~~~~~~~~~~
cc1.exe: all warnings being treated as errors
 [ERRORS]
 |
 |
 |
make[1]: *** [tmk_core/rules.mk:443: .build/obj_planck_rev6_drop_dawz/keyboards/planck/keymaps/dawz/keymap.o] Error 1
Make finished with errors
make: *** [Makefile:539: planck/rev6_drop:dawz] Error 1

The encoder works when I put in a regular keycode like KC_VOLUP or KC_VOLDOWN, but I’m trying to use Ctrl + F23, F24, so I can use the knob as a Voicemeeter macro buttons controller.

ive also used the shortened version (C(KC_F23)) , (C(KC_F24)) also same error — Dawz, Sep 23 '21 at 23:27

score 3 · Answer 1 · answered May 24 '22 at 18:59

You can represent "Ctrl + (basic key)" combinations using the macro LCTL(kc) (and similar macros for other mods), but the technicality is that this creates a 16-bit keycode. So rather than tap_code(), which is limited to 8-bit basic keycodes, use tap_code16() to tap it:

// Copyright 2022 Google LLC.
// SPDX-License-Identifier: Apache-2.0
bool encoder_update_user(uint8_t index, bool clockwise) {
  if (index == 0) {
    tap_code16(clockwise ? LCTL(KC_F24) : LCTL(KC_F23));
  } 
  return false;
}

See also the QMK encoders documentation.

score 0 · Answer 2 · answered Sep 24 '21 at 11:55

If you want to use modifier keys here with encoders you should try using tap_code16 instead of tap_code

Try this instead:

bool encoder_update_user(uint8_t index, bool clockwise) {
    if (index == 0) { /* First encoder */
        if (clockwise) {
            tap_code16(QK_LCTL | KC_F24);
        } else {
            tap_code16(QK_LCTL | KC_F23);
        }
    } 
    return false;
}

Here is the link to the QMK doc for this

Leo · Answer 3 · 2021-11-09T05:40:29.847

You could break down how a key combination is pressed:

Hold down the modifier key
Press some key (usually a letter or number)
Release the modifier key

Then you could represent the whole process:

bool encoder_update_user(uint8_t index, bool clockwise) {
    if (index == 0) { /* First encoder */
        if (clockwise) {
            register_code(QK_LCTL);   // Press and keep holding down
            tap_code(KC_F24);         // Press and release
            unregister_code(QK_LCTL); // Release
        } else {
            register_code(QK_LCTL);
            tap_code(KC_F23);
            unregister_code(QK_LCTL);
        }
    } 
    return false;
}

This approach seems to be dumb, but you can achieve much more complicated cases, such as Ctrl+Alt+Shift+A or something that could hardly do with keycodes.

I did this for one of my self-made keyboard, it works fine.

score -1 · Answer 4 · answered Oct 16 '21 at 13:58

-1

take a look at my keymap at https://github.com/qmk/qmk_firmware/tree/master/keyboards/keebio/iris/keymaps/sq5rix you have working encoders there look at rules.mk, config.h and keymap.c - changes are everywhere

answered Oct 16 '21 at 13:58

Tom

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Thanks to SO. While this link may be useful, it is better to include the essential parts here in your answer. Otherwise, if the external link becomes inaccessible in the future, this answer will become useless. – wovano Oct 16 '21 at 14:42

Struggling with QMK modifier keys

4 Answers4