diff --git a/converter/pc98_usb/Makefile b/converter/pc98_usb/Makefile
index 076371db..2575d866 100644
--- a/converter/pc98_usb/Makefile
+++ b/converter/pc98_usb/Makefile
@@ -11,8 +11,8 @@ TARGET_DIR = .
 SRC =	keymap.c \
 	matrix.c \
 	led.c \
-	command_extra.c \
-	protocol/serial_soft.c
+	protocol/serial_uart.c
+#	protocol/serial_soft.c
 
 CONFIG_H = config.h
 
diff --git a/converter/pc98_usb/command_extra.c b/converter/pc98_usb/command_extra.c
deleted file mode 100644
index 50389467..00000000
--- a/converter/pc98_usb/command_extra.c
+++ /dev/null
@@ -1,43 +0,0 @@
-#include "stdbool.h"
-#include "stdint.h"
-#include "keycode.h"
-#include "serial.h"
-#include "print.h"
-#include "command.h"
-
-bool command_extra(uint8_t code)
-{
-    switch (code) {
-        case KC_H:
-        case KC_SLASH: /* ? */
-            print("\n\n----- Sun converter Help -----\n");
-            print("UP:	Bell On\n");
-            print("DOWN:	Bell Off\n");
-            print("LEFT:	Click On\n");
-            print("RIGHT:	Click Off\n");
-            return false;
-        case KC_UP:
-            print("Bell On\n");
-            serial_send(0x02);
-            break;
-        case KC_DOWN:
-            print("Bell Off\n");
-            serial_send(0x03);
-            break;
-        case KC_LEFT:
-            print("Click On\n");
-            serial_send(0x0A);
-            break;
-        case KC_RIGHT:
-            print("Click Off\n");
-            serial_send(0x0B);
-            break;
-        case KC_NUMLOCK:
-            print("layout\n");
-            serial_send(0x0F);
-            break;
-        default:
-            return false;
-    }
-    return true;
-}
diff --git a/converter/pc98_usb/config.h b/converter/pc98_usb/config.h
index aa0476e3..04ee5b11 100644
--- a/converter/pc98_usb/config.h
+++ b/converter/pc98_usb/config.h
@@ -27,27 +27,18 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 
 /* matrix size */
-#define MATRIX_ROWS 16
-#define MATRIX_COLS 8
+#define MATRIX_ROWS     16
+#define MATRIX_COLS     8
 
 /* To use new keymap framework */
 #define USE_KEYMAP_V2
 
 /* key combination for command */
-#define IS_COMMAND() ( \
+#define IS_COMMAND()    ( \
     host_get_first_key() == KC_CANCEL \
 )
 
 
-/* PC98 Serial(USART) configuration
- *     asynchronous, positive logic, 19200baud, bit order: LSB first
- *     1-start bit, 8-data bit, odd parity, 1-stop bit
- */
-#define SERIAL_BAUD 19200
-#define SERIAL_PARITY_ODD
-#define SERIAL_BIT_ORDER_LSB
-#define SERIAL_LOGIC_POSITIVE
-
 /* PC98 Reset Port shared with TXD */
 #define PC98_RST_DDR    DDRD
 #define PC98_RST_PORT   PORTD
@@ -61,50 +52,92 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #define PC98_RTY_PORT   PORTD
 #define PC98_RTY_BIT    5
 
+/*
+ * PC98 Serial(USART) configuration
+ *     asynchronous, positive logic, 19200baud, bit order: LSB first
+ *     1-start bit, 8-data bit, odd parity, 1-stop bit
+ */
+/*
+ * Software Serial
+ */
+#define SERIAL_SOFT_BAUD                19200
+#define SERIAL_SOFT_PARITY_ODD
+#define SERIAL_SOFT_BIT_ORDER_LSB
+#define SERIAL_SOFT_LOGIC_POSITIVE
 /* RXD Port */
-#define SERIAL_RXD_DDR  DDRD
-#define SERIAL_RXD_PORT PORTD
-#define SERIAL_RXD_PIN  PIND
-#define SERIAL_RXD_BIT  2
-#ifdef SERIAL_LOGIC_NEGATIVE
-#define SERIAL_RXD_READ()       ~(SERIAL_RXD_PIN&(1<<SERIAL_RXD_BIT))
+#define SERIAL_SOFT_RXD_DDR             DDRD
+#define SERIAL_SOFT_RXD_PORT            PORTD
+#define SERIAL_SOFT_RXD_PIN             PIND
+#define SERIAL_SOFT_RXD_BIT             2
+#ifdef SERIAL_SOFT_LOGIC_NEGATIVE
+    #define SERIAL_SOFT_RXD_READ()      ~(SERIAL_SOFT_RXD_PIN&(1<<SERIAL_SOFT_RXD_BIT))
 #else
-#define SERIAL_RXD_READ()       (SERIAL_RXD_PIN&(1<<SERIAL_RXD_BIT))
+    #define SERIAL_SOFT_RXD_READ()      (SERIAL_SOFT_RXD_PIN&(1<<SERIAL_SOFT_RXD_BIT))
 #endif
 /* RXD Interupt */
-#define SERIAL_RXD_VECT INT2_vect
-#define SERIAL_RXD_INIT()  do { \
+#define SERIAL_SOFT_RXD_VECT            INT2_vect
+#define SERIAL_SOFT_RXD_INIT()          do { \
     /* pin configuration: input with pull-up */ \
-    SERIAL_RXD_DDR &= ~(1<<SERIAL_RXD_BIT);     \
-    SERIAL_RXD_PORT |= (1<<SERIAL_RXD_BIT);     \
-    /* enable interrupt: INT2(falling edge) */  \
-    EICRA |= ((1<<ISC21)|(0<<ISC20));           \
-    EIMSK |= (1<<INT2);                         \
-    sei();                                      \
+    SERIAL_SOFT_RXD_DDR &= ~(1<<SERIAL_SOFT_RXD_BIT); \
+    SERIAL_SOFT_RXD_PORT |= (1<<SERIAL_SOFT_RXD_BIT); \
+    /* enable interrupt: INT2(falling edge) */ \
+    EICRA |= ((1<<ISC21)|(0<<ISC20)); \
+    EIMSK |= (1<<INT2); \
+    sei(); \
 } while (0)
-#define SERIAL_RXD_INT_ENTER()
-#define SERIAL_RXD_INT_EXIT() do {  \
-    /* clear interrupt  flag */     \
-    EIFR = (1<<INTF2);              \
+#define SERIAL_SOFT_RXD_INT_ENTER()
+#define SERIAL_SOFT_RXD_INT_EXIT()      do { \
+    /* clear interrupt  flag */ \
+    EIFR = (1<<INTF2); \
 } while (0)
-
 /* TXD Port */
-#define SERIAL_TXD_DDR  DDRD
-#define SERIAL_TXD_PORT PORTD
-#define SERIAL_TXD_PIN  PIND
-#define SERIAL_TXD_BIT  3
-#ifdef SERIAL_LOGIC_NEGATIVE
-#define SERIAL_TXD_ON()     do { SERIAL_TXD_PORT &= ~(1<<SERIAL_TXD_BIT); } while (0)
-#define SERIAL_TXD_OFF()    do { SERIAL_TXD_PORT |=  (1<<SERIAL_TXD_BIT); } while (0)
+#define SERIAL_SOFT_TXD_DDR             DDRD
+#define SERIAL_SOFT_TXD_PORT            PORTD
+#define SERIAL_SOFT_TXD_PIN             PIND
+#define SERIAL_SOFT_TXD_BIT             3
+#ifdef SERIAL_SOFT_LOGIC_NEGATIVE
+    #define SERIAL_SOFT_TXD_ON()        do { \
+        SERIAL_SOFT_TXD_PORT &= ~(1<<SERIAL_SOFT_TXD_BIT); \
+    } while (0)
+    #define SERIAL_SOFT_TXD_OFF()       do { \
+        SERIAL_SOFT_TXD_PORT |=  (1<<SERIAL_SOFT_TXD_BIT); \
+    } while (0)
 #else
-#define SERIAL_TXD_ON()     do { SERIAL_TXD_PORT |=  (1<<SERIAL_TXD_BIT); } while (0)
-#define SERIAL_TXD_OFF()    do { SERIAL_TXD_PORT &= ~(1<<SERIAL_TXD_BIT); } while (0)
+    #define SERIAL_SOFT_TXD_ON()        do { \
+        SERIAL_SOFT_TXD_PORT |=  (1<<SERIAL_SOFT_TXD_BIT); \
+    } while (0)
+    #define SERIAL_SOFT_TXD_OFF()       do { \
+        SERIAL_SOFT_TXD_PORT &= ~(1<<SERIAL_SOFT_TXD_BIT); \
+    } while (0)
 #endif
-#define SERIAL_TXD_INIT()   do { \
-    /* pin configuration: output */         \
-    SERIAL_TXD_DDR |= (1<<SERIAL_TXD_BIT);  \
-    /* idle */                              \
-    SERIAL_TXD_ON();                        \
+#define SERIAL_SOFT_TXD_INIT()          do { \
+    /* pin configuration: output */ \
+    SERIAL_SOFT_TXD_DDR |= (1<<SERIAL_SOFT_TXD_BIT); \
+    /* idle */ \
+    SERIAL_SOFT_TXD_ON(); \
 } while (0)
 
+
+/*
+ * Hardware Serial(UART)
+ */
+#ifdef __AVR_ATmega32U4__
+    #define SERIAL_UART_BAUD       19200
+    #define SERIAL_UART_DATA       UDR1
+    #define SERIAL_UART_UBRR       ((F_CPU/(16UL*SERIAL_UART_BAUD))-1)
+    #define SERIAL_UART_RXD_VECT   USART1_RX_vect
+    #define SERIAL_UART_TXD_READY  (UCSR1A&(1<<UDRE1))
+    #define SERIAL_UART_INIT()     do { \
+        UBRR1L = (uint8_t) SERIAL_UART_UBRR;       /* baud rate */ \
+        UBRR1H = (uint8_t) (SERIAL_UART_UBRR>>8);  /* baud rate */ \
+        UCSR1B |= (1<<RXCIE1) | (1<<RXEN1); /* RX interrupt, RX: enable */ \
+        UCSR1B |= (0<<TXCIE1) | (1<<TXEN1); /* TX interrupt, TX: enable */ \
+        UCSR1C |= (1<<UPM11) | (1<<UPM10);  /* parity: none(00), even(01), odd(11) */ \
+        sei(); \
+    } while(0)
+#else
+    #error "USART configuration is needed."
+#endif
+
+
 #endif
diff --git a/converter/pc98_usb/matrix.c b/converter/pc98_usb/matrix.c
index 18ad5bfe..d03aaf10 100644
--- a/converter/pc98_usb/matrix.c
+++ b/converter/pc98_usb/matrix.c
@@ -89,7 +89,6 @@ RETRY:
     while (!(code = serial_recv())) ;
     print("PC98: send 70: "); print_hex8(code); print("\n");
     if (code != 0xFA) goto RETRY;
-
 }
 
 void matrix_init(void)
diff --git a/protocol/serial_uart.c b/protocol/serial_uart.c
new file mode 100644
index 00000000..6c0af881
--- /dev/null
+++ b/protocol/serial_uart.c
@@ -0,0 +1,93 @@
+/*
+Copyright 2013 Jun WAKO <wakojun@gmail.com>
+
+This software is licensed with a Modified BSD License.
+All of this is supposed to be Free Software, Open Source, DFSG-free,
+GPL-compatible, and OK to use in both free and proprietary applications.
+Additions and corrections to this file are welcome.
+
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+* Redistributions of source code must retain the above copyright
+  notice, this list of conditions and the following disclaimer.
+
+* Redistributions in binary form must reproduce the above copyright
+  notice, this list of conditions and the following disclaimer in
+  the documentation and/or other materials provided with the
+  distribution.
+
+* Neither the name of the copyright holders nor the names of
+  contributors may be used to endorse or promote products derived
+  from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.
+*/
+
+#include <stdbool.h>
+#include <avr/io.h>
+#include <avr/interrupt.h>
+#include "serial.h"
+
+
+void serial_init(void)
+{
+    SERIAL_UART_INIT();
+}
+
+// RX ring buffer
+#define RBUF_SIZE   8
+static uint8_t rbuf[RBUF_SIZE];
+static uint8_t rbuf_head = 0;
+static uint8_t rbuf_tail = 0;
+
+uint8_t serial_recv(void)
+{
+    uint8_t data = 0;
+    if (rbuf_head == rbuf_tail) {
+        return 0;
+    }
+
+    data = rbuf[rbuf_tail];
+    rbuf_tail = (rbuf_tail + 1) % RBUF_SIZE;
+    return data;
+}
+
+int16_t serial_recv2(void)
+{
+    uint8_t data = 0;
+    if (rbuf_head == rbuf_tail) {
+        return -1;
+    }
+
+    data = rbuf[rbuf_tail];
+    rbuf_tail = (rbuf_tail + 1) % RBUF_SIZE;
+    return data;
+}
+
+void serial_send(uint8_t data)
+{
+    while (!SERIAL_UART_TXD_READY) ;
+    SERIAL_UART_DATA = data;
+}
+
+// USART RX complete interrupt
+ISR(SERIAL_UART_RXD_VECT)
+{
+    uint8_t next = (rbuf_head + 1) % RBUF_SIZE;
+    if (next != rbuf_tail) {
+        rbuf[rbuf_head] = SERIAL_UART_DATA;
+        rbuf_head = next;
+    }
+}