+Many of existent projects offer keymap framework to define your own keymap easily. The following will explain how you can define keymap using this framework.
+ Instead, you can also implement your own `keymap_get_action()` to return action code for each key if you want.
+
+This is keymap example for [HHKB](http://en.wikipedia.org/wiki/Happy_Hacking_Keyboard) keyboard. Keymap is defined in `keymaps[]` array.
+
+ static const uint8_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
+ /* Layer 0: Default Layer
+ * ,-----------------------------------------------------------.
+ * |Esc| 1| 2| 3| 4| 5| 6| 7| 8| 9| 0| -| =| \| `|
+ * |-----------------------------------------------------------|
+ * |Tab | Q| W| E| R| T| Y| U| I| O| P| [| ]|Backs|
+ * |-----------------------------------------------------------|
+ * |Contro| A| S| D| F| G| H| J| K| L| ;| '|Enter |
+ * |-----------------------------------------------------------|
+ * |Shift | Z| X| C| V| B| N| M| ,| .| /|Shift |Fn1|
+ * `-----------------------------------------------------------'
+ * |Gui|Alt |Space |Alt |Fn2|
+ * `-------------------------------------------'
+ */
+ KEYMAP(ESC, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, MINS,EQL, BSLS,GRV, \
+ TAB, Q, W, E, R, T, Y, U, I, O, P, LBRC,RBRC,BSPC, \
+ LCTL,A, S, D, F, G, H, J, K, L, FN2, QUOT,ENT, \
+ LSFT,Z, X, C, V, B, N, M, COMM,DOT, SLSH,RSFT,FN1, \
+ LGUI,LALT, SPC, RALT,FN3),
+
+ /* Layer 1: HHKB mode (HHKB Fn)
+ * ,-----------------------------------------------------------.
+ * |Pwr| F1| F2| F3| F4| F5| F6| F7| F8| F9|F10|F11|F12|Ins|Del|
+ * |-----------------------------------------------------------|
+ * |Caps | | | | | | | |Psc|Slk|Pus|Up | |Backs|
+ * |-----------------------------------------------------------|
+ * |Contro|VoD|VoU|Mut| | | *| /|Hom|PgU|Lef|Rig|Enter |
+ * |-----------------------------------------------------------|
+ * |Shift | | | | | | +| -|End|PgD|Dow|Shift |Fn1|
+ * `-----------------------------------------------------------'
+ * |Gui |Alt |Space |Alt |Gui|
+ * `--------------------------------------------'
+ */
+ KEYMAP(PWR, F1, F2, F3, F4, F5, F6, F7, F8, F9, F10, F11, F12, INS, DEL, \
+ CAPS,NO, NO, NO, NO, NO, NO, NO, PSCR,SLCK,PAUS,UP, NO, BSPC, \
+ LCTL,VOLD,VOLU,MUTE,NO, NO, PAST,PSLS,HOME,PGUP,LEFT,RGHT,ENT, \
+ LSFT,NO, NO, NO, NO, NO, PPLS,PMNS,END, PGDN,DOWN,RSFT,FN0, \
+ LGUI,LALT, SPC, RALT,RGUI),
+ /* Layer 2: Mouse mode (Semicolon)
+ * ,-----------------------------------------------------------.
+ * |Esc| F1| F2| F3| F4| F5| F6| F7| F8| F9|F10|F11|F12|Ins|Del|
+ * |-----------------------------------------------------------|
+ * |Tab | | | | | |MwL|MwD|MwU|MwR| | | |Backs|
+ * |-----------------------------------------------------------|
+ * |Contro| | | | | |McL|McD|McU|McR|Fn0| |Return |
+ * |-----------------------------------------------------------|
+ * |Shift | | | | |Mb3|Mb2|Mb1|Mb4|Mb5| |Shift | |
+ * `-----------------------------------------------------------'
+ * |Gui |Alt |Mb1 |Alt |Fn0|
+ * `--------------------------------------------'
+ * Mc: Mouse Cursor / Mb: Mouse Button / Mw: Mouse Wheel
+ */
+ KEYMAP(ESC, F1, F2, F3, F4, F5, F6, F7, F8, F9, F10, F11, F12, INS, DEL, \
+ TAB, NO, NO, NO, NO, NO, WH_L,WH_D,WH_U,WH_R,NO, NO, NO, BSPC, \
+ LCTL,NO, ACL0,ACL1,ACL2,NO, MS_L,MS_D,MS_U,MS_R,FN0, QUOT,ENT, \
+ LSFT,NO, NO, NO, NO, BTN3,BTN2,BTN1,BTN4,BTN5,SLSH,RSFT,NO, \
+ LGUI,LALT, BTN1, RALT,FN0),
+ };
+
+ static const uint16_t PROGMEM fn_actions[] = {
+ ACTION_LAYER_DEFAULT, // FN0
+ ACTION_LAYER_SET(1), // FN1
+ ACTION_LAYER_SET_TAP_KEY(2, KC_SCLN), // FN2
+ ACTION_LAYER_BIT_TOGGLE(2), // FN3
+ };
+
+
+
+### 1. Keycode
+See `common/keycode.h`. Keycode is 8bit internal code to inidicate action performed on key in keymap. Keycode has `KC_` prefixed symbol respectively. Most of keycodes like `KC_A` have simple action register key on press and unregister on release, on the other some of keycodes has some special actions like Fn keys, Media contorl keys, System control keys and Mouse keys.
+
+ ***In `KEYMAP` definition you need to omit prefix part `KC_` of keycode to keep keymap compact.*** For example, just use `A` instead you place `KC_A` in `KEYMAP`. Some keycodes has 4-letter short name in addition to descriptive name, you'll prefer short one in `KEYMAP`.
+
+#### 1.1 Normal key
+- `KC_NO` for no aciton
+- `KC_A` to `KC_Z`, `KC_1` to `KC_0` for alpha numeric key
+- `KC_MINS`, `KC_EQL`, `KC_GRV`, `KC_RBRC`, `KC_LBRC`, `KC_COMM`, `KC_DOT`, `KC_BSLS`, `KC_SLSH`, `KC_SCLN`, `KC_QUOT`
+- `KC_ESC`, `KC_TAB`, `KC_SPC`, `KC_BSPC`, `KC_ENT`, `KC_DEL`, `KC_INS`
+- `KC_UP`, `KC_DOWN`, `KC_RGHT`, `KC_LEFT`, `KC_PGUP`, `KC_PGDN`, `KC_HOME`, `KC_END`
+- `KC_CAPS`, `KC_NLCK`, `KC_SLCK`, `KC_PSCR`, `KC_PAUS`, `KC_APP`, `KC_F1` to `KC_F24`
+- `KC_P1` to `KC_P0`, `KC_PDOT`, `KC_PCMM`, `KC_PSLS`, `KC_PAST`, `KC_PMNS`, `KC_PPLS`, `KC_PEQL`, `KC_PENT` for keypad.
+
+#### 1.2 Modifier
+There are 8 modifiers which has discrimination between left and right.
+
+- `KC_LCTL` and `KC_RCTL` for Control
+- `KC_LSFT` and `KC_RSFT` for Shift
+- `KC_LALT` and `KC_RALT` for Alt
+- `KC_LGUI` and `KC_RGUI` for Windows key or Command key in Mac
+
+#### 1.3 Fn key
+ **`KC_FNnn`** are `Fn` keys which not given any action at the beginning unlike most of keycodes has its own action. To use these keys in `KEYMAP` you need to assign action you want at first. Action of `Fn` is defined in `fn_actions[]` and index of the array is identical with number part of `KC_FNnn`. Thus `KC_FN0` designates action defined in first element of the array. ***32 `Fn` keys can be defined at most.***
+
+#### 1.4 Mousekey
+- `KC_MS_U`, `KC_MS_D`, `KC_MS_L`, `KC_MS_R` for mouse cursor
+- `KC_WH_U`, `KC_WH_D`, `KC_WH_L`, `KC_WH_R` for mouse wheel
+- `KC_BTN1`, `KC_BTN2`, `KC_BTN3`, `KC_BTN4`, `KC_BTN5` for mouse buttons
+
+#### 1.5 System & Media key
+- `KC_PWR`, `KC_SLEP`, `KC_WAKE` for Power, Sleep, Wake
+- `KC_MUTE`, `KC_VOLU`, `KC_VOLD` for audio volume control
+- `KC_MNXT`, `KC_MPRV`, `KC_MSTP`, `KC_MPLY`, `KC_MSEL` for media control
+- `KC_MAIL`, `KC_CALC`, `KC_MYCM` for application launch
+- `KC_WSCH`, `KC_WHOM`, `KC_WBAK`, `KC_WFWD`, `KC_WSTP`, `KC_WREF`, `KC_WFAV` for web browser operation
+
+#### Keycode Table
+ See [keycode table](doc/keycode.txt) in `doc/keycode.txt` or `common/keycode.h` for the detail or other keycodes.
+
+ In regard to implementation side most of keycodes are identical with [HID usage] sent to host for real and some virtual keycodes are defined to support special actions.
+[HID usage]: http://www.usb.org/developers/devclass_docs/Hut1_11.pdf
+
+
+
+### 2. Action
+See `common/action.h`. Action is a 16bit code and defines function to perform on events of a key like press, release, hold and tap. You can define various actions to use various action codes.