diff --git a/keyboard.c b/keyboard.c
index 1a025bd..25948dd 100644
--- a/keyboard.c
+++ b/keyboard.c
@@ -106,6 +106,7 @@ void keyboard_proc(void)
         return;
     }
 
+    // TODO: should send only when changed from last report
     if (matrix_is_modified()) {
         host_send_keyboard_report();
 #ifdef DEBUG_LED
diff --git a/ps2.c b/ps2.c
index 6d76538..52ee169 100644
--- a/ps2.c
+++ b/ps2.c
@@ -96,13 +96,15 @@ void ps2_host_init(void)
 #endif
 }
 
+// TODO: send using interrupt if available
 uint8_t ps2_host_send(uint8_t data)
 {
-    bool parity;
-RETRY:
-    parity = true;
-    ps2_error = 0;
-
+    uint8_t res = 0;
+    bool parity = true;
+    ps2_error = PS2_ERR_NONE;
+#ifdef PS2_INT_DISABLE
+    PS2_INT_DISABLE();
+#endif
     /* terminate a transmission if we have */
     inhibit();
     _delay_us(100);
@@ -139,15 +141,15 @@ RETRY:
     WAIT(clock_hi, 50, 8);
     WAIT(data_hi, 50, 9);
 
-    uint8_t res = ps2_host_recv_response();
-    if (res == 0xFE && data != 0xFE)
-        goto RETRY;
-
-    inhibit();
-    return res;
+    res = ps2_host_recv_response();
 ERROR:
+#ifdef PS2_INT_ENABLE
+    PS2_INT_ENABLE();
+    idle();
+#else
     inhibit();
-    return 0;
+#endif
+    return res;
 }
 
 /* receive data when host want else inhibit communication */
@@ -209,46 +211,99 @@ static inline uint8_t pbuf_dequeue(void)
 /* get data received by interrupt */
 uint8_t ps2_host_recv(void)
 {
+    // TODO: release clock line after 100us when inhibited by error
+    if (ps2_error) {
+        ps2_host_send(0xFE);    // request to resend
+        ps2_error = PS2_ERR_NONE;
+    }
     return pbuf_dequeue();
 }
 
+#define DEBUGP_INIT() do { DDRC = 0xFF; } while (0)
+#define DEBUGP(x) do { PORTC = x; } while (0)
 ISR(PS2_INT_VECT)
 {
-    /* interrupt means start bit comes */
-    pbuf_enqueue(recv_data());
+    static enum {
+        INIT,
+        START,
+        BIT0, BIT1, BIT2, BIT3, BIT4, BIT5, BIT6, BIT7,
+        PARITY,
+        STOP,
+    } state = INIT;
+    static uint8_t data = 0;
+    static uint8_t parity = 1;
 
-    /* release lines(idle state) */
-    idle();
-    _delay_us(5);
+    // TODO: abort if elapse 100us from previous interrupt
+
+    // return unless falling edge
+    if (clock_in()) {
+        goto RETURN;
+    }
+
+    state++;
+    DEBUGP(state);
+    switch (state) {
+        case START:
+            if (data_in())
+                goto ERROR;
+            break;
+        case BIT0:
+        case BIT1:
+        case BIT2:
+        case BIT3:
+        case BIT4:
+        case BIT5:
+        case BIT6:
+        case BIT7:
+            data >>= 1;
+            if (data_in()) {
+                data |= 0x80;
+                parity++;
+            }
+            break;
+        case PARITY:
+            if (data_in()) {
+                if (!(parity & 0x01))
+                    goto ERROR;
+            } else {
+                if (parity & 0x01)
+                    goto ERROR;
+            }
+            break;
+        case STOP:
+            if (!data_in())
+                goto ERROR;
+            pbuf_enqueue(data);
+            goto DONE;
+            break;
+        default:
+            goto ERROR;
+    }
+    goto RETURN;
+ERROR:
+    DEBUGP(0xFF);
+    inhibit();
+    ps2_error = state;
+DONE:
+    state = INIT;
+    data = 0;
+    parity = 1;
+RETURN:
+    return;
 }
 #endif
 
 
-/*
 static void ps2_reset(void)
 {
     ps2_host_send(0xFF);
-    if (ps2_host_recv_response() == 0xFA) {
-        _delay_ms(1000);
-        ps2_host_recv_response();
-    }
 }
-*/
 
 /* send LED state to keyboard */
 void ps2_host_set_led(uint8_t led)
 {
-#ifdef PS2_INT_DISABLE
-    PS2_INT_DISABLE();
-#endif
     ps2_host_send(0xED);
-    ps2_host_recv_response();
     ps2_host_send(led);
-    ps2_host_recv_response();
-#ifdef PS2_INT_ENABLE
-    PS2_INT_ENABLE();
-    idle();
-#endif
 }
 
 
@@ -257,7 +312,7 @@ static uint8_t recv_data(void)
 {
     uint8_t data = 0;
     bool parity = true;
-    ps2_error = 0;
+    ps2_error = PS2_ERR_NONE;
 
     /* start bit [1] */
     WAIT(clock_lo, 1, 1);
@@ -307,6 +362,7 @@ static inline bool clock_in()
 {
     PS2_CLOCK_DDR  &= ~(1<<PS2_CLOCK_BIT);
     PS2_CLOCK_PORT |=  (1<<PS2_CLOCK_BIT);
+    _delay_us(1);
     return PS2_CLOCK_PIN&(1<<PS2_CLOCK_BIT);
 }
 static inline void data_lo()
@@ -324,6 +380,7 @@ static inline bool data_in()
 {
     PS2_DATA_DDR  &= ~(1<<PS2_DATA_BIT);
     PS2_DATA_PORT |=  (1<<PS2_DATA_BIT);
+    _delay_us(1);
     return PS2_DATA_PIN&(1<<PS2_DATA_BIT);
 }
 
diff --git a/ps2_vusb/main.c b/ps2_vusb/main.c
index 74c7a17..5afbde0 100644
--- a/ps2_vusb/main.c
+++ b/ps2_vusb/main.c
@@ -49,7 +49,7 @@ int main(void)
     usbInit();
 
     print_enable = true;
-    //debug_enable = true;
+    debug_enable = true;
     keyboard_init();
 
     /* enforce re-enumeration, do this while interrupts are disabled! */
@@ -64,56 +64,9 @@ int main(void)
 
     //uint8_t fn_bits = 0;
     while (1) {                /* main event loop */
-        DEBUGP(0x01);
         wdt_reset();
         usbPoll();
-        host_vusb_keyboard_send();
-
-        DEBUGP(0x02);
         keyboard_proc();
-        DEBUGP(0x03);
-/*
-        matrix_scan();
-        fn_bits = 0;
-        host_swap_keyboard_report();
-        host_clear_keyboard_report();
-        mousekey_clear_report();
-        for (int row = 0; row < matrix_rows(); row++) {
-            for (int col = 0; col < matrix_cols(); col++) {
-                if (!matrix_is_on(row, col)) continue;
-
-                uint8_t code = layer_get_keycode(row, col);
-                if (code == KB_NO) {
-                    // do nothing
-                }
-                else if (IS_MOD(code)) {
-                    host_add_mod_bit(MOD_BIT(code));
-                }
-                else if (IS_KEY(code)) {
-                    host_add_key(code);
-                }
-                else if (IS_FN(code)) {
-                    fn_bits |= FN_BIT(code);
-                }
-                else if (IS_MOUSEKEY(code)) {
-                    mousekey_decode(code);
-                }
-                else {
-                    debug("ignore keycode: "); debug_hex(code); debug("\n");
-                }
-            }
-        }
-        DEBUGP(0x03);
-        layer_switching(fn_bits);
-        if (matrix_is_modified()) {
-            host_send_keyboard_report();
-        }
-        mousekey_send();
-
-        if (last_led != host_keyboard_led()) {
-            led_set(host_keyboard_led());
-            last_led = host_keyboard_led();
-        }
-*/
+        host_vusb_keyboard_send();
     }
 }
diff --git a/vusb/host.c b/vusb/host.c
index a32a1b1..f637aba 100644
--- a/vusb/host.c
+++ b/vusb/host.c
@@ -258,33 +258,6 @@ PROGMEM uchar keyboard_hid_report[] = {
  */
 PROGMEM uchar mouse_hid_report[] = {
     /* from HID 1.11 spec example */
-    0x05, 0x01,     // Usage Page (Generic Desktop),
-    0x09, 0x02,     // Usage (Mouse),
-    0xA1, 0x01,     // Collection (Application),
-    0x09, 0x01,     //   Usage (Pointer),
-    0xA1, 0x00,     //   Collection (Physical),
-    0x05, 0x09,     //     Usage Page (Buttons),
-    0x19, 0x01,     //     Usage Minimum (01),
-    0x29, 0x03,     //     Usage Maximun (03),
-    0x15, 0x00,     //     Logical Minimum (0),
-    0x25, 0x01,     //     Logical Maximum (1),
-    0x95, 0x03,     //     Report Count (3),
-    0x75, 0x01,     //     Report Size (1),
-    0x81, 0x02,     //     Input (Data, Variable, Absolute), ;3 button bits
-    0x95, 0x01,     //     Report Count (1),
-    0x75, 0x05,     //     Report Size (5),
-    0x81, 0x01,     //     Input (Constant), ;5 bit padding
-    0x05, 0x01,     //     Usage Page (Generic Desktop),
-    0x09, 0x30,     //     Usage (X),
-    0x09, 0x31,     //     Usage (Y),
-    0x15, 0x81,     //     Logical Minimum (-127),
-    0x25, 0x7F,     //     Logical Maximum (127),
-    0x75, 0x08,     //     Report Size (8),
-    0x95, 0x02,     //     Report Count (2),
-    0x81, 0x06,     //     Input (Data, Variable, Relative), ;2 position bytes (X & Y)
-    0xC0,           //   End Collection,
-    0xC0,           // End Collection
-/*
     0x05, 0x01,        // USAGE_PAGE (Generic Desktop)
     0x09, 0x02,        // USAGE (Mouse)
     0xa1, 0x01,        // COLLECTION (Application)
@@ -355,7 +328,6 @@ PROGMEM uchar mouse_hid_report[] = {
     0xc0,              //     END_COLLECTION
     0xc0,              //   END_COLLECTION
     0xc0               // END_COLLECTION
-*/
 };