diff --git a/hhkb/config.h b/hhkb/config.h
index 7722ed46..cc86e55c 100644
--- a/hhkb/config.h
+++ b/hhkb/config.h
@@ -1,18 +1,20 @@
 #ifndef CONFIG_H
 #define CONFIG_H
 
+/* controller configuration */
+#include "controller_teensy.h"
+
 #define VENDOR_ID       0xFEED
 #define PRODUCT_ID      0xCAFE
 #define MANUFACTURER    t.m.k.
 #define PRODUCT         HHKB mod
 #define DESCRIPTION     t.m.k. keyboard firmware for HHKB mod
 
-/* controller */
-#include "controller_teensy.h"
-
 /* matrix size */
 #define MATRIX_ROWS 8
 #define MATRIX_COLS 8
+/* define if matrix has ghost */
+//#define MATRIX_HAS_GHOST
 
 /* USB NKey Rollover */
 #ifdef USB_NKRO_ENABLE
diff --git a/hhkb/keymap.c b/hhkb/keymap.c
index 4273835e..e18bb862 100644
--- a/hhkb/keymap.c
+++ b/hhkb/keymap.c
@@ -12,6 +12,8 @@
 #include "keymap_skel.h"
 
 
+// Convert physical keyboard layout to matrix array.
+// This is a macro to define keymap easily in keyboard layout form.
 #define KEYMAP( \
     R3C1, R3C0, R0C0, R1C0, R1C1, R2C0, R2C1, R4C0, R4C1, R6C0, R6C1, R7C0, R7C1, R5C0, R5C1, \
     R3C2, R0C1, R0C2, R1C3, R1C2, R2C3, R2C2, R4C2, R4C3, R6C2, R6C3, R7C3, R7C2, R5C2, \
@@ -33,19 +35,29 @@
 #define KEYCODE(layer, row, col) (pgm_read_byte(&keymaps[(layer)][(row)][(col)]))
 
 
-/* layer to change into while Fn key pressed */ 
-static const int PROGMEM fn_layer[] = { 0, 1, 2, 3, 4, 0, 0, 1 };
+// Assign Fn key(0-7) to a layer to which switch with the Fn key pressed.
+static const uint8_t PROGMEM fn_layer[] = {
+    0,              // FN_0
+    1,              // FN_1
+    2,              // FN_2
+    3,              // FN_3
+    4,              // FN_4
+    0,              // FN_5
+    0,              // FN_6
+    1               // FN_7
+};
 
-/* keycode to sent when Fn key released without using layer keys. */
+// Assign Fn key(0-7) to a keycode sent when release Fn key without use of the layer.
+// See layer.c for details.
 static const uint8_t PROGMEM fn_keycode[] = {
-    KB_NO,          // FN_0 [NOT USED]
-    KB_NO,          // FN_1 layer 1
-    KB_SLSH,        // FN_2 layer 2
-    KB_SCLN,        // FN_3 layer 3
-    KB_SPC,         // FN_4 layer 4
-    KB_NO,          // FN_5 [NOT USED]
-    KB_NO,          // FN_6 [NOT USED]
-    KB_NO           // FN_7 layer 1
+    KB_NO,          // FN_0
+    KB_NO,          // FN_1
+    KB_SLSH,        // FN_2
+    KB_SCLN,        // FN_3
+    KB_SPC,         // FN_4
+    KB_NO,          // FN_5
+    KB_NO,          // FN_6
+    KB_NO           // FN_7
 };
 
 static const uint8_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
@@ -152,7 +164,7 @@ uint8_t keymap_get_keycode(uint8_t layer, uint8_t row, uint8_t col)
     return KEYCODE(layer, row, col);
 }
 
-int keymap_fn_layer(uint8_t fn_bits)
+uint8_t keymap_fn_layer(uint8_t fn_bits)
 {
     return pgm_read_byte(&fn_layer[biton(fn_bits)]);
 }
@@ -162,6 +174,7 @@ uint8_t keymap_fn_keycode(uint8_t fn_bits)
     return pgm_read_byte(&fn_keycode[(biton(fn_bits))]);
 }
 
+// define a condition to enter special function mode
 bool keymap_is_special_mode(uint8_t fn_bits)
 {
     return (usb_keyboard_mods == (BIT_LCTRL | BIT_LSHIFT | BIT_LALT | BIT_LGUI));
diff --git a/hhkb/matrix.c b/hhkb/matrix.c
index dd4440d9..15633d53 100644
--- a/hhkb/matrix.c
+++ b/hhkb/matrix.c
@@ -9,6 +9,33 @@
 #include "util.h"
 #include "matrix_skel.h"
 
+
+#if (MATRIX_COLS > 16)
+#   error "MATRIX_COLS must not exceed 16"
+#endif
+#if (MATRIX_ROWS > 255)
+#   error "MATRIX_ROWS must not exceed 255"
+#endif
+
+
+// matrix state buffer(1:on, 0:off)
+#if (MATRIX_COLS <= 8)
+static uint8_t *matrix;
+static uint8_t *matrix_prev;
+static uint8_t _matrix0[MATRIX_ROWS];
+static uint8_t _matrix1[MATRIX_ROWS];
+#else
+static uint16_t *matrix;
+static uint16_t *matrix_prev;
+static uint16_t _matrix0[MATRIX_ROWS];
+static uint16_t _matrix1[MATRIX_ROWS];
+#endif
+
+#ifdef MATRIX_HAS_GHOST
+static bool matrix_has_ghost_in_row(uint8_t row);
+#endif
+
+
 // matrix is active low. (key on: 0/key off: 1)
 //
 // HHKB has no ghost and no bounce.
@@ -28,26 +55,19 @@
 #define KEY_PREV_ON             (PORTE |= (1<<7))
 #define KEY_PREV_OFF            (PORTE &= ~(1<<7))
 
-// matrix state buffer
-static uint8_t *matrix;
-static uint8_t *matrix_prev;
-static uint8_t _matrix0[MATRIX_ROWS];
-static uint8_t _matrix1[MATRIX_ROWS];
-
 
 inline
-int matrix_rows(void)
+uint8_t matrix_rows(void)
 {
     return MATRIX_ROWS;
 }
 
 inline
-int matrix_cols(void)
+uint8_t matrix_cols(void)
 {
     return MATRIX_COLS;
 }
 
-// this must be called once before matrix_scan.
 void matrix_init(void)
 {
     // row & col output(PB0-6)
@@ -59,13 +79,13 @@ void matrix_init(void)
     PORTE = 0x40;
 
     // initialize matrix state: all keys off
-    for (int i=0; i < MATRIX_ROWS; i++) _matrix0[i] = 0x00;
-    for (int i=0; i < MATRIX_ROWS; i++) _matrix1[i] = 0x00;
+    for (uint8_t i=0; i < MATRIX_ROWS; i++) _matrix0[i] = 0x00;
+    for (uint8_t i=0; i < MATRIX_ROWS; i++) _matrix1[i] = 0x00;
     matrix = _matrix0;
     matrix_prev = _matrix1;
 }
 
-int matrix_scan(void)
+uint8_t matrix_scan(void)
 {
     uint8_t *tmp;
 
@@ -73,8 +93,8 @@ int matrix_scan(void)
     matrix_prev = matrix;
     matrix = tmp;
 
-    for (int row = 0; row < MATRIX_ROWS; row++) {
-        for (int col = 0; col < MATRIX_COLS; col++) {
+    for (uint8_t row = 0; row < MATRIX_ROWS; row++) {
+        for (uint8_t col = 0; col < MATRIX_COLS; col++) {
             KEY_SELELCT(row, col);
             _delay_us(40);  // from logic analyzer chart
             if (matrix_prev[row] & (1<<col)) {
@@ -98,7 +118,7 @@ int matrix_scan(void)
 
 bool matrix_is_modified(void)
 {
-    for (int i = 0; i < MATRIX_ROWS; i++) {
+    for (uint8_t i = 0; i < MATRIX_ROWS; i++) {
         if (matrix[i] != matrix_prev[i])
             return true;
     }
@@ -108,36 +128,80 @@ bool matrix_is_modified(void)
 inline
 bool matrix_has_ghost(void)
 {
+#ifdef MATRIX_HAS_GHOST
+    for (uint8_t i = 0; i < MATRIX_ROWS; i++) {
+        if (matrix_has_ghost_in_row(i))
+            return true;
+    }
+#endif
     return false;
 }
 
 inline
-bool matrix_is_on(int row, int col)
+bool matrix_is_on(uint8_t row, uint8_t col)
 {
     return (matrix[row] & (1<<col));
 }
 
 inline
-uint16_t matrix_get_row(int row)
+#if (MATRIX_COLS <= 8)
+uint8_t matrix_get_row(uint8_t row)
+#else
+uint16_t matrix_get_row(uint8_t row)
+#endif
 {
     return matrix[row];
 }
 
 void matrix_print(void)
 {
+#if (MATRIX_COLS <= 8)
     print("\nr/c 01234567\n");
-    for (int row = 0; row < matrix_rows(); row++) {
+#else
+    print("\nr/c 0123456789ABCDEF\n");
+#endif
+    for (uint8_t row = 0; row < matrix_rows(); row++) {
         phex(row); print(": ");
+#if (MATRIX_COLS <= 8)
         pbin_reverse(matrix_get_row(row));
+#else
+        pbin_reverse16(matrix_get_row(row));
+#endif
+#ifdef MATRIX_HAS_GHOST
+        if (matrix_has_ghost_in_row(row)) {
+            print(" <ghost");
+        }
+#endif
         print("\n");
     }
 }
 
-int matrix_key_count(void)
+uint8_t matrix_key_count(void)
 {
-    int count = 0;
-    for (int i = 0; i < MATRIX_ROWS; i++) {
+    uint8_t count = 0;
+    for (uint8_t i = 0; i < MATRIX_ROWS; i++) {
+#if (MATRIX_COLS <= 8)
         count += bitpop(matrix[i]);
+#else
+        count += bitpop16(matrix[i]);
+#endif
     }
     return count;
 }
+
+#ifdef MATRIX_HAS_GHOST
+inline
+static bool matrix_has_ghost_in_row(uint8_t row)
+{
+    // no ghost exists in case less than 2 keys on
+    if (((matrix[row] - 1) & matrix[row]) == 0)
+        return false;
+
+    // ghost exists in case same state as other row
+    for (uint8_t i=0; i < MATRIX_ROWS; i++) {
+        if (i != row && (matrix[i] & matrix[row]) == matrix[row])
+            return true;
+    }
+    return false;
+}
+#endif
diff --git a/macway/config.h b/macway/config.h
index 41bdc33d..1403ef12 100644
--- a/macway/config.h
+++ b/macway/config.h
@@ -1,18 +1,20 @@
 #ifndef CONFIG_H
 #define CONFIG_H
 
+/* controller configuration */
+#include "controller_teensy.h"
+
 #define VENDOR_ID       0xFEED
 #define PRODUCT_ID      0xBEE0
 #define MANUFACTURER    t.m.k.
 #define PRODUCT         Macway mod
 #define DESCRIPTION     t.m.k. keyboard firmware for Macway mod
 
-/* controller */
-#include "controller_teensy.h"
-
 /* matrix size */
 #define MATRIX_ROWS 9
 #define MATRIX_COLS 8
+/* define if matrix has ghost */
+#define MATRIX_HAS_GHOST
 
 /* USB NKey Rollover */
 #ifdef USB_NKRO_ENABLE
diff --git a/macway/keymap.c b/macway/keymap.c
index 0e71e3f7..118036e9 100644
--- a/macway/keymap.c
+++ b/macway/keymap.c
@@ -4,7 +4,6 @@
 #include <stdint.h>
 #include <stdbool.h>
 #include <avr/pgmspace.h>
-#include <avr/interrupt.h>
 #include "usb_keyboard.h"
 #include "usb_keycodes.h"
 #include "print.h"
@@ -13,6 +12,8 @@
 #include "keymap_skel.h"
 
 
+// Convert physical keyboard layout to matrix array.
+// This is a macro to define keymap easily in keyboard layout form.
 #define KEYMAP( \
     R1C1, R1C0, R2C0, R3C0, R4C0, R4C1, R5C1, R5C0, R6C0, R7C0, R8C0, R8C1, R6C1, R0C2, \
     R1C2, R1C3, R2C3, R3C3, R4C3, R4C2, R5C2, R5C3, R6C3, R7C3, R8C3, R8C2, R6C2, \
@@ -34,17 +35,29 @@
 #define KEYCODE(layer, row, col) (pgm_read_byte(&keymaps[(layer)][(row)][(col)]))
 
 
-static const uint8_t PROGMEM fn_layer[] = { 0, 1, 2, 3, 4, 0, 2, 3 };
+// Assign Fn key(0-7) to a layer to which switch with the Fn key pressed.
+static const uint8_t PROGMEM fn_layer[] = {
+    0,              // FN_0
+    1,              // FN_1
+    2,              // FN_2
+    3,              // FN_3
+    4,              // FN_4
+    0,              // FN_5
+    2,              // FN_6
+    3               // FN_7
+};
 
+// Assign Fn key(0-7) to a keycode sent when release Fn key without use of the layer.
+// See layer.c for details.
 static const uint8_t PROGMEM fn_keycode[] = {
-    KB_NO,          // FN_0 [NOT USED]
-    KB_NO,          // FN_1 layer 1
-    KB_SLSH,        // FN_2 layer 2
-    KB_SCLN,        // FN_3 layer 3
-    KB_SPC,         // FN_4 layer 4
-    KB_NO,          // FN_5 [NOT USED]
-    KB_NO,          // FN_6 layer 2
-    KB_NO           // FN_7 layer 3
+    KB_NO,          // FN_0
+    KB_NO,          // FN_1
+    KB_SLSH,        // FN_2
+    KB_SCLN,        // FN_3
+    KB_SPC,         // FN_4
+    KB_NO,          // FN_5
+    KB_NO,          // FN_6
+    KB_NO           // FN_7
 };
 
 static const uint8_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
@@ -155,7 +168,7 @@ uint8_t keymap_get_keycode(uint8_t layer, uint8_t row, uint8_t col)
     return KEYCODE(layer, row, col);
 }
 
-int keymap_fn_layer(uint8_t fn_bits)
+uint8_t keymap_fn_layer(uint8_t fn_bits)
 {
     return pgm_read_byte(&fn_layer[biton(fn_bits)]);
 }
@@ -165,6 +178,7 @@ uint8_t keymap_fn_keycode(uint8_t fn_bits)
     return pgm_read_byte(&fn_keycode[(biton(fn_bits))]);
 }
 
+// define a condition to enter special function mode
 bool keymap_is_special_mode(uint8_t fn_bits)
 {
     //return (usb_keyboard_mods == (BIT_LCTRL | BIT_LSHIFT | BIT_LALT | BIT_LGUI));
diff --git a/macway/matrix.c b/macway/matrix.c
index 7c2a4210..f8c0640f 100644
--- a/macway/matrix.c
+++ b/macway/matrix.c
@@ -10,31 +10,47 @@
 #include "matrix_skel.h"
 
 
-// matrix state buffer (key on: 1/key off: 0)
+#if (MATRIX_COLS > 16)
+#   error "MATRIX_COLS must not exceed 16"
+#endif
+#if (MATRIX_ROWS > 255)
+#   error "MATRIX_ROWS must not exceed 255"
+#endif
+
+
+// matrix state buffer(1:on, 0:off)
+#if (MATRIX_COLS <= 8)
 static uint8_t *matrix;
 static uint8_t *matrix_prev;
 static uint8_t _matrix0[MATRIX_ROWS];
 static uint8_t _matrix1[MATRIX_ROWS];
+#else
+static uint16_t *matrix;
+static uint16_t *matrix_prev;
+static uint16_t _matrix0[MATRIX_ROWS];
+static uint16_t _matrix1[MATRIX_ROWS];
+#endif
 
+#ifdef MATRIX_HAS_GHOST
 static bool matrix_has_ghost_in_row(uint8_t row);
+#endif
 static uint8_t read_col(void);
 static void unselect_rows(void);
 static void select_row(uint8_t row);
 
 
 inline
-int matrix_rows(void)
+uint8_t matrix_rows(void)
 {
     return MATRIX_ROWS;
 }
 
 inline
-int matrix_cols(void)
+uint8_t matrix_cols(void)
 {
     return MATRIX_COLS;
 }
 
-// this must be called once before matrix_scan.
 void matrix_init(void)
 {
     // initialize row and col
@@ -44,13 +60,13 @@ void matrix_init(void)
     PORTB = 0xFF;
 
     // initialize matrix state: all keys off
-    for (int i=0; i < MATRIX_ROWS; i++) _matrix0[i] = 0x00;
-    for (int i=0; i < MATRIX_ROWS; i++) _matrix1[i] = 0x00;
+    for (uint8_t i=0; i < MATRIX_ROWS; i++) _matrix0[i] = 0x00;
+    for (uint8_t i=0; i < MATRIX_ROWS; i++) _matrix1[i] = 0x00;
     matrix = _matrix0;
     matrix_prev = _matrix1;
 }
 
-int matrix_scan(void)
+uint8_t matrix_scan(void)
 {
     uint8_t *tmp;
 
@@ -58,7 +74,7 @@ int matrix_scan(void)
     matrix_prev = matrix;
     matrix = tmp;
 
-    for (int i = 0; i < MATRIX_ROWS; i++) {
+    for (uint8_t i = 0; i < MATRIX_ROWS; i++) {
         unselect_rows();
         select_row(i);
         _delay_us(30);  // without this wait read unstable value.
@@ -70,30 +86,37 @@ int matrix_scan(void)
 
 bool matrix_is_modified(void)
 {
-    for (int i = 0; i < MATRIX_ROWS; i++) {
+    for (uint8_t i = 0; i < MATRIX_ROWS; i++) {
         if (matrix[i] != matrix_prev[i])
             return true;
     }
     return false;
 }
 
+inline
 bool matrix_has_ghost(void)
 {
-    for (int i = 0; i < MATRIX_ROWS; i++) {
+#ifdef MATRIX_HAS_GHOST
+    for (uint8_t i = 0; i < MATRIX_ROWS; i++) {
         if (matrix_has_ghost_in_row(i))
             return true;
     }
+#endif
     return false;
 }
 
 inline
-bool matrix_is_on(int row, int col)
+bool matrix_is_on(uint8_t row, uint8_t col)
 {
     return (matrix[row] & (1<<col));
 }
 
 inline
-uint16_t matrix_get_row(int row)
+#if (MATRIX_COLS <= 8)
+uint8_t matrix_get_row(uint8_t row)
+#else
+uint16_t matrix_get_row(uint8_t row)
+#endif
 {
     return matrix[row];
 }
@@ -101,25 +124,37 @@ uint16_t matrix_get_row(int row)
 void matrix_print(void)
 {
     print("\nr/c 01234567\n");
-    for (int row = 0; row < matrix_rows(); row++) {
+    for (uint8_t row = 0; row < matrix_rows(); row++) {
         phex(row); print(": ");
+#if (MATRIX_COLS <= 8)
         pbin_reverse(matrix_get_row(row));
+#else
+        pbin_reverse16(matrix_get_row(row));
+#endif
+#ifdef MATRIX_HAS_GHOST
         if (matrix_has_ghost_in_row(row)) {
             print(" <ghost");
         }
+#endif
         print("\n");
     }
 }
 
-int matrix_key_count(void)
+uint8_t matrix_key_count(void)
 {
-    int count = 0;
-    for (int i = 0; i < MATRIX_ROWS; i++) {
+    uint8_t count = 0;
+    for (uint8_t i = 0; i < MATRIX_ROWS; i++) {
+#if (MATRIX_COLS <= 8)
         count += bitpop(matrix[i]);
+#else
+        count += bitpop16(matrix[i]);
+#endif
     }
     return count;
 }
 
+#ifdef MATRIX_HAS_GHOST
+inline
 static bool matrix_has_ghost_in_row(uint8_t row)
 {
     // no ghost exists in case less than 2 keys on
@@ -127,18 +162,21 @@ static bool matrix_has_ghost_in_row(uint8_t row)
         return false;
 
     // ghost exists in case same state as other row
-    for (int i=0; i < MATRIX_ROWS; i++) {
+    for (uint8_t i=0; i < MATRIX_ROWS; i++) {
         if (i != row && (matrix[i] & matrix[row]) == matrix[row])
             return true;
     }
     return false;
 }
+#endif
 
+inline
 static uint8_t read_col(void)
 {
     return PINB;
 }
 
+inline
 static void unselect_rows(void)
 {
     // Hi-Z(DDR:0, PORT:0) to unselect
@@ -150,6 +188,7 @@ static void unselect_rows(void)
     PORTF &= ~0b11000000;
 }
 
+inline
 static void select_row(uint8_t row)
 {
     // Output low(DDR:1, PORT:0) to select
diff --git a/matrix_skel.h b/matrix_skel.h
index 59c4eca1..2379ce44 100644
--- a/matrix_skel.h
+++ b/matrix_skel.h
@@ -4,23 +4,27 @@
 #include <stdbool.h>
 
 /* number of matrix rows */
-int  matrix_rows(void);
+uint8_t matrix_rows(void);
 /* number of matrix columns */
-int  matrix_cols(void);
+uint8_t 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);
+uint8_t 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);
 /* whether a swtich is on */
-bool matrix_is_on(int row, int col);
+bool matrix_is_on(uint8_t row, uint8_t col);
 /* matrix state on row */
-uint16_t matrix_get_row(int row);
+#if (MATRIX_COLS <= 8)
+uint8_t matrix_get_row(uint8_t row);
+#else
+uint16_t matrix_get_row(uint8_t row);
+#endif
 /* count keys pressed */
-int matrix_key_count(void);
+uint8_t matrix_key_count(void);
 /* print matrix for debug */
 void matrix_print(void);