qmk-dactyl-manuform-a/keyboards/np12/keymaps/via/keymap.c

 /* Copyright 2021 nut1414
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation, either version 2 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */

#include QMK_KEYBOARD_H

const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {


	[0] = LAYOUT(
						           KC_MPLY,
		KC_9,    KC_6,    KC_3,    KC_PENT,
		KC_8,    KC_5,    KC_2,    KC_BSPC,
		KC_7,    KC_4,    KC_1,    KC_0),

	[1] = LAYOUT(
						           KC_TRNS,
		KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS,
		KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS,
		KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS),

	[2] = LAYOUT(
						           KC_TRNS,
		KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS,
		KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS,
		KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS),

	[3] = LAYOUT(
						           KC_TRNS,
		KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS,
		KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS,
		KC_TRNS, KC_TRNS, KC_TRNS, KC_TRNS),



};

bool encoder_update_user(uint8_t index, bool clockwise) {
    if (index == 0) {
        if (clockwise) {
            tap_code(KC_AUDIO_VOL_UP);
        } else {
            tap_code(KC_AUDIO_VOL_DOWN);
        }
    }
    return true;
}