diff --git a/ADB.txt b/ADB.txt
index b98cf676..186015c9 100644
--- a/ADB.txt
+++ b/ADB.txt
@@ -3,11 +3,14 @@ ADB Protocol
 
 Resources
 ---------
+ADB - The Untold Story: Space Aliens Ate My Mouse
+    http://developer.apple.com/legacy/mac/library/#technotes/hw/hw_01.html
 Apple IIgs Hardware Reference Second Edition [p80(Chapter6 p121)]
     ftp://ftp.apple.asimov.net/pub/apple_II/documentation/Apple%20IIgs%20Hardware%20Reference.pdf
 ADB Keycode
     http://72.0.193.250/Documentation/macppc/adbkeycodes/
     http://m0115.web.fc2.com/m0115.jpg
+    [Inside Macintosh volume V, pages 191-192]
 ADB Signaling
     http://kbdbabel.sourceforge.net/doc/kbd_signaling_pcxt_ps2_adb.pdf
 ADB Overview & History
@@ -61,9 +64,9 @@ Commands
     3:  mice
 
     Registers:
-    0: application(keyobard/mice use to store its data.)
+    0: application(keyobard uses this to store its data.)
     1: application
-    2: application
+    2: application(keyboard uses this for LEDs and state of modifiers)
     3: status and command
 
 
@@ -111,15 +114,17 @@ Communication
     keep low for 300us to request.
 
 
-Keyboard data(register0)
-    This 16bit data can contains 2 keycodes and 2 released flags.
-    First keycode is palced in upper nibble. When one keyocode is sent,
-    lower nibble is 0xFF.
+Keyboard Data(Register0)
+    This 16bit data can contains two keycodes and two released flags.
+    First keycode is palced in upper byte. When one keyocode is sent,
+    lower byte is 0xFF.
     Release flag is 1 when key is released.
 
-    15 14 . . . . . 8 7 6 . . . . . 0
-    |  |keycode1      | |keycode2
-    |released(1)      |released(1)
+    1514 . . . . . 8 7 6 . . . . . 0
+     | | | | | | | | | +-+-+-+-+-+-+-   Keycode2
+     | | | | | | | | +---------------   Released2(1 when the key is released)
+     | +-+-+-+-+-+-+-----------------   Keycode1
+     +-------------------------------   Released1(1 when the key is released)
 
     Keycodes:
     Scancode consists of 7bit keycode and 1bit release flag.
@@ -131,4 +136,24 @@ Keyboard data(register0)
     the switch has a special scancode 0x7F7F, so you can
     also read from Data line. It uses 0xFFFF for release scancode.
 
+Keyboard LEDs & state of keys(Register2)
+    This register hold current state of three LEDs and nine keys.
+    The state of LEDs can be changed by sending Listen command.
+    
+    1514 . . . . . . 7 6 5 . 3 2 1 0
+     | | | | | | | | | | | | | | | +-   LED1(NumLock)
+     | | | | | | | | | | | | | | +---   LED2(CapsLock)
+     | | | | | | | | | | | | | +-----   LED3(ScrollLock)
+     | | | | | | | | | | +-+-+-------   Reserved
+     | | | | | | | | | +-------------   ScrollLock
+     | | | | | | | | +---------------   NumLock
+     | | | | | | | +-----------------   Apple/Command
+     | | | | | | +-------------------   Option
+     | | | | | +---------------------   Shift
+     | | | | +-----------------------   Control
+     | | | +-------------------------   Reset/Power
+     | | +---------------------------   CapsLock
+     | +-----------------------------   Delete
+     +-------------------------------   Reserved
+
 END_OF_ADB
diff --git a/adb.c b/adb.c
index e66a501b..6848fa65 100644
--- a/adb.c
+++ b/adb.c
@@ -42,9 +42,9 @@ uint16_t adb_host_kbd_recv(void)
 {
     uint16_t data = 0;
     attention();
-    send_byte(0x2C);            // Addr:2, Cmd:talk(11), Reg:0(00)
-    place_bit0();               // Stopbit
-    if (!wait_data_lo(0xFF))    // Stop to Start(140-260us)
+    send_byte(0x2C);            // Addr:Keyboard(0010), Cmd:Talk(11), Register0(00)
+    place_bit0();               // Stopbit(0)
+    if (!wait_data_lo(0xFF))    // Tlt/Stop to Start(140-260us)
         return 0;               // No data to send
     if (!read_bit())            // Startbit(1)
         return -2;
@@ -55,6 +55,19 @@ uint16_t adb_host_kbd_recv(void)
     return data;
 }
 
+// send state of LEDs
+void adb_host_kbd_led(uint8_t led)
+{
+    attention();
+    send_byte(0x2A);            // Addr:Keyboard(0010), Cmd:Listen(10), Register2(10)
+    place_bit0();               // Stopbit(0)
+    _delay_us(200);             // Tlt/Stop to Start
+    place_bit1();               // Startbit(1)
+    send_byte(0);               // send upper byte (not used)
+    send_byte(led&0x07);        // send lower byte (bit2: ScrollLock, bit1: CapsLock, bit0: NumLock)
+    place_bit0();               // Stopbit(0);
+}
+
 
 static inline void data_lo()
 {
diff --git a/adb.h b/adb.h
index 8f167354..8a9cee10 100644
--- a/adb.h
+++ b/adb.h
@@ -14,5 +14,6 @@
 void     adb_host_init(void);
 bool     adb_host_psw(void);
 uint16_t adb_host_kbd_recv(void);
+void     adb_host_kbd_led(uint8_t led);
 
 #endif
diff --git a/adb/README b/adb/README
index edd118d4..d6c9ec9a 100644
--- a/adb/README
+++ b/adb/README
@@ -1,8 +1,10 @@
 ADB to USB keyboard converter
 =============================
+http://geekhack.org/showwiki.php?title=Island:14290
 
 This firmware converts ADB keyboard protocol to USB.
 
+
 Build
 -----
 0. Connect ADB keyboard to Teensy by 3 lines(Vcc, GND, Data).
diff --git a/adb/matrix.c b/adb/matrix.c
index ca8858d0..550506ec 100644
--- a/adb/matrix.c
+++ b/adb/matrix.c
@@ -9,6 +9,7 @@
 #include "util.h"
 #include "debug.h"
 #include "adb.h"
+#include "usb_keyboard.h"
 #include "matrix_skel.h"
 
 
@@ -71,8 +72,13 @@ uint8_t matrix_scan(void)
     uint16_t codes;
     uint8_t key0, key1;
 
-    _matrix_is_modified = false;
+    static uint8_t prev_led = 0;
+    if (prev_led != usb_keyboard_leds) {
+        adb_host_kbd_led(~usb_keyboard_leds);
+        prev_led = usb_keyboard_leds;
+    }
 
+    _matrix_is_modified = false;
     codes = adb_host_kbd_recv();
     key0 = codes>>8;
     key1 = codes&0xFF;