diff --git a/Makefile.common b/Makefile.common
index 8037b077..879e5238 100644
--- a/Makefile.common
+++ b/Makefile.common
@@ -51,10 +51,10 @@
 # List C source files here. (C dependencies are automatically generated.)
 SRC =	tmk.c \
 	key_process.c \
-	usb.c \
 	usb_keyboard.c \
 	usb_mouse.c \
 	usb_debug.c \
+	usb.c \
 	jump_bootloader.c \
 	print.c
 SRC +=	$(TARGET_SRC)
diff --git a/hhkb/keymap.c b/hhkb/keymap.c
index 572f530b..6838a08a 100644
--- a/hhkb/keymap.c
+++ b/hhkb/keymap.c
@@ -3,12 +3,18 @@
  */
 #include <stdbool.h>
 #include <avr/pgmspace.h>
+#include "usb_keyboard.h"
 #include "matrix.h"
 #include "keymap.h"
-#include "usb_keyboard.h"
+#include "print.h"
 
-int current_layer = 0;
-bool key_sent = false;
+#define FN_KEYCODE(fn) (pgm_read_byte(&fn_keycode[(fn)]))
+#define FN_LAYER(fn)   (pgm_read_byte(&fn_layer[(fn)]))
+#define KEYMAPS(layer, row, col) (pgm_read_byte(&keymaps[(layer)][(row)][(col)]))
+
+static int current_layer = 0;
+static bool layer_used = false;
+static int onbit(uint8_t bits);
 
 /*
  * Layer0(Default Layer)
@@ -66,15 +72,21 @@ bool key_sent = false;
  * Mc: Mouse Cursor / Mb: Mouse Button / Mw: Mouse Wheel 
  */
 
-/* keycode sent when Fn key released without using layer keys. */
-static const uint8_t PROGMEM FnKey[] = {
-    KB_NO,          // this must be KB_NO. (not used)
+/* keycode to sent when Fn key released without using layer keys. */
+static const uint8_t PROGMEM fn_keycode[] = {
+    KB_NO,          // FN_0
     KB_NO,          // FN_1
     KB_RALT,        // FN_2
     KB_SCOLON,      // FN_3
+    KB_NO,          // FN_4
+    KB_NO,          // FN_5
+    KB_NO,          // FN_6
+    KB_NO,          // FN_7
 };
+/* layer to change into while Fn key pressed */ 
+static const int PROGMEM fn_layer[] = { 0, 1, 2, 3, 0, 0, 0, 0 };
 
-static const uint8_t PROGMEM Keymap[][MATRIX_ROWS][MATRIX_COLS] = {
+static const uint8_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
 /*  plain keymap
     {
         { KB_2,       KB_Q,       KB_W,       KB_S,       KB_A,       KB_Z,       KB_X,       KB_C        },
@@ -134,61 +146,77 @@ static const uint8_t PROGMEM Keymap[][MATRIX_ROWS][MATRIX_COLS] = {
 };
 
 
-uint8_t get_keycode(int layer, int row, int col)
+uint8_t keymap_get_keycode(int row, int col)
 {
-    if (row >= MATRIX_ROWS)
-        return KB_NO;
-    if (col >= MATRIX_COLS)
-        return KB_NO;
-    return pgm_read_byte(&Keymap[layer][row][col]);
+    return keymap_get_keycodel(current_layer, row, col);
 }
 
-int get_layer(void) {
-    // keep modifier state when Fn key pressed
-    static uint8_t preserved_modifiers = 0;
-    int layer = 0;
-    uint8_t modifiers = 0;
-    for (int row = 0; row < MATRIX_ROWS; row++) {
-        for (int col = 0; col < MATRIX_ROWS; col++) {
-            if (matrix[row] & 1<<col) continue; // NOT pressed
-            uint8_t code = get_keycode(0, row, col);
-
-            // NOT change current_layer when one more Fn keys pressed
-            //                          when other than Fn key pressed
-            if      (code == FN_1) layer = layer ? current_layer : 1;
-            else if (code == FN_2) layer = layer ? current_layer : 2;
-            else if (code == FN_3) layer = layer ? current_layer : 3;
-            else if (code == FN_4) layer = layer ? current_layer : 4;
-            else if (KB_LCTRL <= code && code <= KB_RGUI)
-                modifiers |= 1<<(code & 0x07);
-            else // other_key_pressed
-                layer = current_layer;
-        }
-    }
-
-    // TODO: this logic should go anywhere
-    // TODO: need timeout for key_sent
-    // send key when Fn key reloeased without used
-    if (layer != current_layer) {
-        if (layer == 0 && !key_sent) {
-            uint8_t code = pgm_read_byte(&FnKey[current_layer]);
-            if (code) {
-                // send modifiers when Fn key pressed.
-                keyboard_modifier_keys = preserved_modifiers;
-                for (int i = 0; i < 6; i++) keyboard_keys[i] = KB_NO;
-
-                if (KB_LCTRL <= code && code <= KB_RGUI) {
-                    keyboard_modifier_keys |= 1<<(code & 0x07);
-                } else  {
-                    keyboard_keys[0] = code;
-                }
-                usb_keyboard_send();
-            }
-        }
-        current_layer = layer;
-        key_sent = false;
-        preserved_modifiers = modifiers;
-    }
+uint8_t keymap_get_keycodel(int layer, int row, int col)
+{
+    uint8_t code = KEYMAPS(layer, row, col);
+    // normal key or mouse key
+    if ((KB_A <= code && code <= KP_HEXADECIMAL) ||
+        (MS_UP <= code && code <= MS_WH_RIGHT))
+        layer_used = true;
+    return code;
+}
 
+inline
+int keymap_get_layer(void) {
     return current_layer;
 }
+
+inline
+int keymap_set_layer(int layer) {
+    current_layer = layer;
+    return current_layer;
+}
+
+void keymap_fn_proc(int fn_bits) {
+    // layer switching
+    static int last_bits = 0;
+    static uint8_t last_mod = 0;
+
+    if (usb_keyboard_has_key() || fn_bits == last_bits) {
+        // do nothing during press other than Fn key 
+        return;
+    } else if (fn_bits == 0) {
+        // send key when Fn key is released without using the layer
+        if (!layer_used) {
+            uint8_t code = FN_KEYCODE(onbit(last_bits));
+            if (code != KB_NO) {
+                if (KB_LCTRL <= code  && code <= KB_RGUI) {
+                    keyboard_modifier_keys = last_mod | 1<<(code & 0x07);
+                } else {
+                    keyboard_keys[0] = code;
+                    keyboard_modifier_keys = last_mod;
+                }
+                usb_keyboard_send();
+                usb_keyboard_print();
+                usb_keyboard_clear();
+            }
+        }
+        last_bits = 0;
+        last_mod = 0;
+        layer_used = false;
+        keymap_set_layer(0); // default layer
+        print("layer default: "); phex(current_layer); print("\n");
+    } else if ((fn_bits & (fn_bits - 1)) == 0) {
+        // switch layer when just one Fn Key is pressed
+        last_bits = fn_bits;
+        last_mod = keyboard_modifier_keys;
+        layer_used = false;
+        keymap_set_layer(FN_LAYER(onbit(fn_bits)));
+        print("layer: "); phex(current_layer); print("\n");
+        print("last_bits: "); phex(last_bits); print("\n");
+        print("last_mod: "); phex(last_mod); print("\n");
+    }
+}
+
+static int onbit(uint8_t bits) {
+    int n = 0;
+    if (bits >> 4) { bits >>= 4; n += 4;}
+    if (bits >> 2) { bits >>= 2; n += 2;}
+    if (bits >> 1) { bits >>= 1; n += 1;}
+    return n;
+}
diff --git a/hhkb/keymap.h b/hhkb/keymap.h
index be78609e..a577c79b 100644
--- a/hhkb/keymap.h
+++ b/hhkb/keymap.h
@@ -4,17 +4,6 @@
 #include <stdint.h>
 #include <stdbool.h>
 #include "usb_keycodes.h"
-
-
-#define MATRIX_ROWS 8
-#define MATRIX_COLS 8
-
-
-extern int current_layer;
-extern bool key_sent;
-
-
-int get_layer(void);
-uint8_t get_keycode(int layer, int row, int col);
+#include "keymap_skel.h"
 
 #endif
diff --git a/hhkb/matrix.c b/hhkb/matrix.c
index 3034a636..a1917793 100644
--- a/hhkb/matrix.c
+++ b/hhkb/matrix.c
@@ -31,6 +31,19 @@ static uint8_t _matrix0[MATRIX_ROWS];
 static uint8_t _matrix1[MATRIX_ROWS];
 
 
+static bool matrix_has_ghost_in_row(int row);
+
+
+inline
+int matrix_rows(void) {
+    return MATRIX_ROWS;
+}
+
+inline
+int matrix_cols(void) {
+    return MATRIX_COLS;
+}
+
 // this must be called once before matrix_scan.
 void matrix_init(void)
 {
@@ -48,7 +61,7 @@ void matrix_init(void)
     matrix_prev = _matrix1;
 }
 
-uint8_t matrix_scan(void)
+int matrix_scan(void)
 {
     uint8_t *tmp;
 
@@ -82,10 +95,29 @@ bool matrix_is_modified(void) {
     return false;
 }
 
+inline
 bool matrix_has_ghost(void) {
     return false;
 }
 
-bool matrix_has_ghost_in_row(uint8_t row) {
+inline
+uint16_t matrix_get_row(int row) {
+    return matrix[row];
+}
+
+void matrix_print(void) {
+    print("\nr/c 01234567\n");
+    for (int row = 0; row < matrix_rows(); row++) {
+        phex(row); print(": ");
+        pbin_reverse(matrix_get_row(row));
+        if (matrix_has_ghost_in_row(row)) {
+            print(" <ghost");
+        }
+        print("\n");
+    }
+}
+
+inline
+static bool matrix_has_ghost_in_row(int row) {
     return false;
 }
diff --git a/hhkb/matrix.h b/hhkb/matrix.h
new file mode 100644
index 00000000..5efffea5
--- /dev/null
+++ b/hhkb/matrix.h
@@ -0,0 +1,15 @@
+#ifndef MATRIX_H
+#define  MATRIX_H 1
+
+#include <stdbool.h>
+#include "matrix_skel.h"
+
+
+#define MATRIX_ROWS 8
+#define MATRIX_COLS 8
+
+
+extern uint8_t *matrix;
+extern uint8_t *matrix_prev;
+
+#endif
diff --git a/key_process.c b/key_process.c
index 4a9e81b7..8006ae72 100644
--- a/key_process.c
+++ b/key_process.c
@@ -8,7 +8,7 @@
 #include "usb_keyboard.h"
 #include "usb_mouse.h"
 #include "print.h"
-#include "matrix.h"
+#include "matrix_skel.h"
 #include "keymap.h"
 #include "jump_bootloader.h"
 
@@ -25,150 +25,113 @@
 #define MOUSE_DELAY_ACC 5
 
 
-
-static void print_matrix(void);
-static void print_keys(void);
-static void print_mouse(int8_t mouse_x, int8_t mouse_y, int8_t wheel_v, int8_t wheel_h);
-
 void proc_matrix(void) {
     static int mouse_repeat = 0;
 
     bool modified = false;
-    bool has_ghost = false;
-    int layer = 0;
+    //bool has_ghost = false;
     int key_index = 0;
     uint8_t mouse_btn = 0;
     int8_t mouse_x = 0;
     int8_t mouse_y = 0;
     int8_t mouse_wheel = 0;
     int8_t mouse_hwheel = 0;
+    int fn_bits = 0;
 
-        matrix_scan();
-        modified = matrix_is_modified();
-        has_ghost = matrix_has_ghost();
-        layer = get_layer();
+    matrix_scan();
+    modified = matrix_is_modified();
 
-        // print matrix state for debug
-        if (modified) {
-            print_matrix();
+    if (modified) {
+        matrix_print();
 
-            // LED flash for debug
-            LED_CONFIG;
-            LED_ON;
+        // LED flash for debug
+        LED_CONFIG;
+        LED_ON;
+    }
+
+    if (matrix_has_ghost()) {
+        // should send error?
+        print("matrix has ghost!!\n");
+        return;
+    }
+
+    usb_keyboard_clear();
+    for (int row = 0; row < matrix_rows(); row++) {
+        for (int col = 0; col < matrix_cols(); col++) {
+            if (matrix_get_row(row) & 1<<col) continue;
+
+            uint8_t code = keymap_get_keycode(row, col);
+            if (code == KB_NO) {
+                code = keymap_get_keycodel(0, row, col);
+                if (FN_0 <= code && code <= FN_7) {
+                    fn_bits |= 1<<(code - FN_0);
+                }
+            } else if (KB_LCTRL <= code && code <= KB_RGUI) {
+                // modifier keys(0xE0-0xE7)
+                keyboard_modifier_keys |= 1<<(code & 0x07);
+            } else if (code >= MS_UP) {
+                // mouse
+                if (code == MS_UP)    mouse_y -= MOUSE_MOVE_UNIT + (mouse_repeat < 50 ? mouse_repeat/5 : 10);
+                if (code == MS_DOWN)  mouse_y += MOUSE_MOVE_UNIT + (mouse_repeat < 50 ? mouse_repeat/5 : 10);
+                if (code == MS_LEFT)  mouse_x -= MOUSE_MOVE_UNIT + (mouse_repeat < 50 ? mouse_repeat/5 : 10);
+                if (code == MS_RIGHT) mouse_x += MOUSE_MOVE_UNIT + (mouse_repeat < 50 ? mouse_repeat/5 : 10);
+                if (code == MS_BTN1)  mouse_btn |= 1<<0;
+                if (code == MS_BTN2)  mouse_btn |= 1<<1;
+                if (code == MS_BTN3)  mouse_btn |= 1<<2;
+                if (code == MS_BTN4)  mouse_btn |= 1<<3;
+                if (code == MS_BTN5)  mouse_btn |= 1<<4;
+                if (code == MS_WH_UP)  mouse_wheel += 1;
+                if (code == MS_WH_DOWN)  mouse_wheel -= 1;
+                if (code == MS_WH_LEFT)  mouse_hwheel -= 1;
+                if (code == MS_WH_RIGHT) mouse_hwheel += 1;
+            } else if (FN_0 <= code && code <= FN_7) {
+                fn_bits |= 1<<(code - FN_0);
+            } else {
+                // normal keys
+                if (key_index < 6)
+                    keyboard_keys[key_index] = code;
+                key_index++;
+            }
         }
+    }
+    keymap_fn_proc(fn_bits);
 
+    // when 4 left modifier keys down
+    if (keyboard_modifier_keys == (MOD_LCTRL | MOD_LSHIFT | MOD_LALT | MOD_LGUI)) {
+        // cancel all keys
         keyboard_modifier_keys = 0;
         for (int i = 0; i < 6; i++) keyboard_keys[i] = KB_NO;
-        key_index = 0;
-        mouse_btn = 0;
-        mouse_x = 0;
-        mouse_y = 0;
-        mouse_wheel = 0;
-        mouse_hwheel = 0;
+        usb_keyboard_send();
 
-        // convert matrix state to HID report
-        for (int row = 0; row < MATRIX_ROWS; row++) {
-            for (int col = 0; col < MATRIX_COLS; col++) {
-                if (matrix[row] & 1<<col) continue;
+        print("jump to bootloader...\n");
+        _delay_ms(100);
+        jump_bootloader(); // not return
+    }
 
-                uint8_t code = get_keycode(layer, row, col);
-                if (code == KB_NO) {
-                    continue;
-                } else if (KB_LCTRL <= code && code <= KB_RGUI) {
-                    // modifier keys(0xE0-0xE7)
-                    keyboard_modifier_keys |= 1<<(code & 0x07);
-                } else if (code >= MS_UP) {
-                    // mouse
-                    if (code == MS_UP)    mouse_y -= MOUSE_MOVE_UNIT + (mouse_repeat < 50 ? mouse_repeat/5 : 10);
-                    if (code == MS_DOWN)  mouse_y += MOUSE_MOVE_UNIT + (mouse_repeat < 50 ? mouse_repeat/5 : 10);
-                    if (code == MS_LEFT)  mouse_x -= MOUSE_MOVE_UNIT + (mouse_repeat < 50 ? mouse_repeat/5 : 10);
-                    if (code == MS_RIGHT) mouse_x += MOUSE_MOVE_UNIT + (mouse_repeat < 50 ? mouse_repeat/5 : 10);
-                    if (code == MS_BTN1)  mouse_btn |= 1<<0;
-                    if (code == MS_BTN2)  mouse_btn |= 1<<1;
-                    if (code == MS_BTN3)  mouse_btn |= 1<<2;
-                    if (code == MS_BTN4)  mouse_btn |= 1<<3;
-                    if (code == MS_BTN5)  mouse_btn |= 1<<4;
-                    if (code == MS_WH_UP)  mouse_wheel += 1;
-                    if (code == MS_WH_DOWN)  mouse_wheel -= 1;
-                    if (code == MS_WH_LEFT)  mouse_hwheel -= 1;
-                    if (code == MS_WH_RIGHT) mouse_hwheel += 1;
-                } else {
-                    // normal keys
-                    if (key_index < 6)
-                        keyboard_keys[key_index] = code;
-                    key_index++;
-                }
-            }
+
+    if (mouse_x || mouse_y || mouse_wheel || mouse_hwheel || mouse_btn != mouse_buttons) {
+        mouse_buttons = mouse_btn;
+        usb_mouse_move(mouse_x, mouse_y, mouse_wheel, mouse_hwheel);
+        usb_mouse_print(mouse_x, mouse_y, mouse_wheel, mouse_hwheel);
+
+        // acceleration
+        _delay_ms(MOUSE_DELAY_MS >> (mouse_repeat < MOUSE_DELAY_ACC ? mouse_repeat : MOUSE_DELAY_ACC));
+        mouse_repeat++;
+    } else {
+        mouse_repeat = 0;
+    }
+
+
+    // send keys to host
+    if (modified) {
+        if (key_index > 6) {
+            //Rollover
         }
+        usb_keyboard_send();
 
-        if (!has_ghost)  {
-            // when 4 left modifier keys down
-            if (keyboard_modifier_keys == (MOD_LCTRL | MOD_LSHIFT | MOD_LALT | MOD_LGUI)) {
-                // cancel all keys
-                keyboard_modifier_keys = 0;
-                for (int i = 0; i < 6; i++) keyboard_keys[i] = KB_NO;
-                usb_keyboard_send();
-
-                print("jump to bootloader...\n");
-                _delay_ms(100);
-                jump_bootloader(); // not return
-            }
-
-            if (mouse_x || mouse_y || mouse_wheel || mouse_hwheel || mouse_btn != mouse_buttons) {
-                mouse_buttons = mouse_btn;
-                usb_mouse_move(mouse_x, mouse_y, mouse_wheel, mouse_hwheel);
-                print_mouse(mouse_x, mouse_y, mouse_wheel, mouse_hwheel);
-                key_sent = true;
-
-                // acceleration
-                _delay_ms(MOUSE_DELAY_MS >> (mouse_repeat < MOUSE_DELAY_ACC ? mouse_repeat : MOUSE_DELAY_ACC));
-                mouse_repeat++;
-            } else {
-                mouse_repeat = 0;
-            }
-
-
-            // send keys to host
-            if (modified) {
-                if (key_index > 6) {
-                    //Rollover
-                }
-                usb_keyboard_send();
-                if (keyboard_keys[0])
-                    key_sent = true;
-
-                print_keys();
-                // LED flash for debug
-                LED_CONFIG;
-                LED_OFF;
-            }
-        }
-}
-
-static void print_matrix(void) {
-    print("\nr/c 01234567\n");
-    for (int row = 0; row < MATRIX_ROWS; row++) {
-        phex(row); print(": ");
-        pbin_reverse(matrix[row]);
-        if (matrix_has_ghost_in_row(row)) {
-            print(" <ghost");
-        }
-        print("\n");
+        usb_keyboard_print();
+        // LED flash for debug
+        LED_CONFIG;
+        LED_OFF;
     }
 }
-
-static void print_keys(void) {
-    print("\nkeys: ");
-    for (int i = 0; i < 6; i++) { phex(keyboard_keys[i]); print(" "); }
-    print("\n");
-    print("mods: "); phex(keyboard_modifier_keys); print("\n");
-}
-
-static void print_mouse(int8_t mouse_x, int8_t mouse_y, int8_t wheel_v, int8_t wheel_h) {
-    print("\nmouse_x y v h: ");
-    phex(mouse_x); print(" ");
-    phex(mouse_y); print(" ");
-    phex(wheel_v); print(" ");
-    phex(wheel_h); print("\n");
-    print("buttons: "); phex(mouse_buttons); print("\n");
-}
diff --git a/key_process.h b/key_process.h
index 10577dd5..bfc0218f 100644
--- a/key_process.h
+++ b/key_process.h
@@ -1,6 +1,7 @@
 #ifndef KEY_PROCESS_H
 #define  KEY_PROCESS_H 1
 
+
 void proc_matrix(void);
 
 #endif
diff --git a/keymap_skel.h b/keymap_skel.h
new file mode 100644
index 00000000..51906d36
--- /dev/null
+++ b/keymap_skel.h
@@ -0,0 +1,17 @@
+#ifndef KEYMAP_SKEL_H
+#define KEYMAP_SKEL_H 1
+
+#include <stdint.h>
+#include <stdbool.h>
+#include "usb_keycodes.h"
+
+
+uint8_t keymap_get_keycode(int row, int col);
+uint8_t keymap_get_keycodel(int layer, int row, int col);
+int keymap_get_layer(void);
+int keymap_set_layer(int layer);
+
+/* process Fn keys. This.should be called every scan. */
+void keymap_fn_proc(int fn_bits);
+
+#endif
diff --git a/matrix.h b/matrix.h
deleted file mode 100644
index 74b5f894..00000000
--- a/matrix.h
+++ /dev/null
@@ -1,15 +0,0 @@
-#ifndef MATRIX_H
-#define  MATRIX_H 1
-
-#include <stdbool.h>
-
-extern uint8_t *matrix;
-extern uint8_t *matrix_prev;
-
-void matrix_init(void);
-uint8_t matrix_scan(void);
-bool matrix_is_modified(void);
-bool matrix_has_ghost(void);
-bool matrix_has_ghost_in_row(uint8_t row);
-
-#endif
diff --git a/matrix_skel.h b/matrix_skel.h
new file mode 100644
index 00000000..0d483034
--- /dev/null
+++ b/matrix_skel.h
@@ -0,0 +1,24 @@
+#ifndef MATRIX_SKEL_H
+#define  MATRIX_SKEL_H 1
+
+#include <stdbool.h>
+
+/* number of matrix rows */
+int  matrix_rows(void);
+/* number of matrix columns */
+int  matrix_cols(void);
+/* intialize matrix for scaning. should be called once. */
+void matrix_init(void);
+/* scan all key states on matrix */
+int  matrix_scan(void);
+/* whether modified from previous scan. used after matrix_scan. */
+bool matrix_is_modified(void);
+/* whether ghosting occur on matrix. */
+bool matrix_has_ghost(void);
+/* matrix state on row */
+uint16_t matrix_get_row(int row);
+/* print matrix for debug */
+void matrix_print(void);
+
+
+#endif
diff --git a/tmk.c b/tmk.c
index c0197251..cd52d318 100644
--- a/tmk.c
+++ b/tmk.c
@@ -34,7 +34,7 @@
 #include "usb_keyboard.h"
 #include "usb_mouse.h"
 #include "print.h"
-#include "matrix.h"
+#include "matrix_skel.h"
 #include "keymap.h"
 #include "jump_bootloader.h"
 
diff --git a/usb_keyboard.c b/usb_keyboard.c
index 9d41e8bc..44365bb8 100644
--- a/usb_keyboard.c
+++ b/usb_keyboard.c
@@ -1,8 +1,11 @@
 #include <avr/interrupt.h>
 #include <avr/pgmspace.h>
 #include "usb_keyboard.h"
+#include "print.h"
 
 
+static bool is_sent = false;
+
 // which modifier keys are currently pressed
 // 1=left ctrl,    2=left shift,   4=left alt,    8=left gui
 // 16=right ctrl, 32=right shift, 64=right alt, 128=right gui
@@ -72,5 +75,45 @@ int8_t usb_keyboard_send(void)
 	UEINTX = 0x3A;
 	keyboard_idle_count = 0;
 	SREG = intr_state;
+        is_sent = true;
 	return 0;
 }
+
+void usb_keyboard_init(void) {
+    usb_keyboard_clear();
+    is_sent = false;
+}
+
+void usb_keyboard_clear(void) {
+    usb_keyboard_clear_key();
+    usb_keyboard_clear_mod();
+}
+
+void usb_keyboard_clear_key(void) {
+    for (int i = 0; i < 6; i++) keyboard_keys[i] = 0;
+}
+
+void usb_keyboard_clear_mod(void) {
+    keyboard_modifier_keys = 0;
+}
+
+bool usb_keyboard_is_sent(void) {
+    return is_sent;
+}
+
+bool usb_keyboard_has_key(void) {
+    uint8_t keys = 0;    
+    for (int i = 0; i < 6; i++) keys |= keyboard_keys[i];
+    return keys ? true : false;
+}
+
+bool usb_keyboard_has_mod(void) {
+    return keyboard_modifier_keys ? true : false;
+}
+
+void usb_keyboard_print(void) {
+    print("\nkeys: ");
+    for (int i = 0; i < 6; i++) { phex(keyboard_keys[i]); print(" "); }
+    print("\n");
+    print("mods: "); phex(keyboard_modifier_keys); print("\n");
+}
diff --git a/usb_keyboard.h b/usb_keyboard.h
index 90c2c5af..2420745e 100644
--- a/usb_keyboard.h
+++ b/usb_keyboard.h
@@ -2,6 +2,7 @@
 #define  USB_KEYBOARD_H 1
 
 #include <stdint.h>
+#include <stdbool.h>
 #include "usb.h"
 
 
@@ -10,6 +11,7 @@
 #define KEYBOARD_SIZE		8
 #define KEYBOARD_BUFFER		EP_DOUBLE_BUFFER
 
+// TODO: move to usb_keycodes.h ?
 // modifier bits
 #define MOD_LCTRL   (1<<0)
 #define MOD_LSHIFT  (1<<1)
@@ -21,15 +23,24 @@
 #define MOD_RGUI    (1<<7)
 
 
+// TODO: change variable name: usb_keyboard_ or usb_kb_
 extern uint8_t keyboard_modifier_keys;
 extern uint8_t keyboard_keys[6];
 extern uint8_t keyboard_protocol;
 extern uint8_t keyboard_idle_config;
 extern uint8_t keyboard_idle_count;
-extern volatile uint8_t keyboard_leds;
+extern volatile uint8_t keyboard_leds; // TODO: delete NOT USED?
 
 
 int8_t usb_keyboard_press(uint8_t key, uint8_t modifier);
 int8_t usb_keyboard_send(void);
+void usb_keyboard_init(void);
+void usb_keyboard_clear(void);
+void usb_keyboard_clear_key(void);
+void usb_keyboard_clear_mod(void);
+bool usb_keyboard_is_sent(void);
+bool usb_keyboard_has_key(void);
+bool usb_keyboard_has_mod(void);
+void usb_keyboard_print(void);
 
 #endif
diff --git a/usb_keycodes.h b/usb_keycodes.h
index 9573344c..3652bcab 100644
--- a/usb_keycodes.h
+++ b/usb_keycodes.h
@@ -262,10 +262,14 @@ enum keycodes {
     KB_RGUI,            /* 0x80 */
 
     /* extensions for internal use */
-    FN_1 = 0xE8,
+    FN_0 = 0xE8,
+    FN_1,
     FN_2,
     FN_3,
     FN_4,
+    FN_5,
+    FN_6,
+    FN_7,
     MS_UP = 0xF0,
     MS_DOWN,
     MS_LEFT,
diff --git a/usb_mouse.c b/usb_mouse.c
index c2617a5e..6eb47dde 100644
--- a/usb_mouse.c
+++ b/usb_mouse.c
@@ -1,8 +1,11 @@
 #include <avr/interrupt.h>
 #include <util/delay.h>
 #include "usb_mouse.h"
+#include "print.h"
 
 
+static bool is_sent = false;
+
 // which buttons are currently pressed
 uint8_t mouse_buttons=0;
 
@@ -60,5 +63,23 @@ int8_t usb_mouse_move(int8_t x, int8_t y, int8_t wheel, int8_t hwheel)
         
 	UEINTX = 0x3A;
 	SREG = intr_state;
+        is_sent = true;
 	return 0;
 }
+
+void usb_mouse_clear(void) {
+    is_sent = false;
+}
+
+bool usb_mouse_is_sent(void) {
+    return is_sent;
+}
+
+void usb_mouse_print(int8_t mouse_x, int8_t mouse_y, int8_t wheel_v, int8_t wheel_h) {
+    print("mouse btn|x y v h: ");
+    phex(mouse_buttons); print("|");
+    phex(mouse_x); print(" ");
+    phex(mouse_y); print(" ");
+    phex(wheel_v); print(" ");
+    phex(wheel_h); print("\n");
+}
diff --git a/usb_mouse.h b/usb_mouse.h
index 81edabcb..b62dde13 100644
--- a/usb_mouse.h
+++ b/usb_mouse.h
@@ -2,6 +2,7 @@
 #define  USB_MOUSE_H 1
 
 #include <stdint.h>
+#include <stdbool.h>
 #include "usb.h"
 
 
@@ -16,5 +17,8 @@ extern uint8_t mouse_protocol;
 
 int8_t usb_mouse_buttons(uint8_t left, uint8_t middle, uint8_t right);
 int8_t usb_mouse_move(int8_t x, int8_t y, int8_t wheel, int8_t hwheel);
+void usb_mouse_clear(void);
+bool usb_mouse_is_sent(void);
+void usb_mouse_print(int8_t mouse_x, int8_t mouse_y, int8_t wheel_v, int8_t wheel_h);
 
 #endif