qmk_firmware/keyboards/thevankeyboards/roadkit/keymaps/default/keymap.c

#include QMK_KEYBOARD_H

extern keymap_config_t keymap_config;

// Each layer gets a name for readability, which is then used in the keymap matrix below.
// The underscores don't mean anything - you can have a layer called STUFF or any other name.
// Layer names don't all need to be of the same length, obviously, and you can also skip them
// entirely and just use numbers.

#define _NP 0

// Macro name shortcuts
#define NUMPAD M(_NP)

// Fillers to make layering more clear
#define _______ KC_TRNS
#define XXXXXXX KC_NO


const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
  [_NP] = LAYOUT_numpad_4x4( /* Numpad */
    KC_P7, KC_P8,   KC_P9,   KC_PPLS, \
    KC_P4, KC_P5,   KC_P6,            \
    KC_P1, KC_P2,   KC_P3,   KC_PENT, \
    KC_P0,          KC_PDOT           \
  ),
};

void persistent_default_layer_set(uint16_t default_layer) {
  eeconfig_update_default_layer(default_layer);
  default_layer_set(default_layer);
}

const macro_t *action_get_macro(keyrecord_t *record, uint8_t id, uint8_t opt)
{
      switch(id) {
        case _NP:
          if (record->event.pressed) {
            persistent_default_layer_set(1UL<<_NP);
          }
          break;
      }
    return MACRO_NONE;
};