diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4165c4b..b74b42c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -22,7 +22,7 @@ include_directories(Middlewares/ST/STM32_USB_Device_Library/Class/HID/Inc)
 include_directories(Middlewares/ST/STM32_USB_Device_Library/Core/Inc)
 
 add_definitions(-DSTM32F103x6)
-add_executable(${PROJECT_NAME}.elf ${USER_SOURCES} ${LINKER_SCRIPT} Inc/main.h)
+add_executable(${PROJECT_NAME}.elf ${USER_SOURCES} ${LINKER_SCRIPT})
 
 target_link_libraries(${PROJECT_NAME}.elf HAL CMSIS USBFS)
 
diff --git a/Inc/circbuf.h b/Inc/circbuf.h
new file mode 100644
index 0000000..9331628
--- /dev/null
+++ b/Inc/circbuf.h
@@ -0,0 +1,96 @@
+/**
+ * @file circbuf.h
+ * @author Ondřej Hruška, 2016
+ *
+ * Circular buffer / queue / stack.
+ * Slots are pre-allocated, values are copied into the buffer.
+ *
+ * The buffer may be used as a stack, event queue or a simple buffer.
+ *
+ * -------------------------------------
+ *
+ *         NW        LR
+ * append -> [][][][] -> pop
+ *                    <- push
+ *
+ * NW - next write pointer (stack base)
+ * LR - last read position (stack top)
+ *
+ * -------------------------------------
+ *
+ * MIT license
+ */
+
+#ifndef F103_USB_CIRCBUF_H
+#define F103_USB_CIRCBUF_H
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <stdlib.h>
+
+
+typedef struct circbuf_struct CircBuf;
+
+
+/**
+ * @brief Initialize a circular buffer. The buffer is malloc'd.
+ * @param capacity  : buffer capacity
+ * @param elem_size : size of one element
+ * @return pointer to the buffer instance
+ */
+CircBuf *cbuf_create(size_t capacity, size_t elem_size);
+
+
+/**
+ * @brief Destroy a buffer, freeing used memory.
+ *
+ * @attention
+ * If the buffer items have malloc'd members, you have
+ * to free them manually to avoid a memory leak.
+ *
+ * @param cb : buffer
+ */
+void cbuf_destroy(CircBuf *cb);
+
+
+/** Test for full buffer */
+bool cbuf_full(const CircBuf *cb);
+
+
+/** Test for empty buffer */
+bool cbuf_empty(const CircBuf *cb);
+
+
+/**
+ * @brief Append a value to the buffer (FIFO)
+ * @param cb     : buffer
+ * @param source : pointer to a value (will be copied)
+ * @return success
+ */
+bool cbuf_append(CircBuf *cb, const void *source);
+
+
+/**
+ * @brief Push a value into the circbuf (LIFO).
+ *
+ * @param cb     : buffer
+ * @param source : pointer to a value (will be copied)
+ * @return success
+ */
+bool cbuf_push(CircBuf *cb, const void *source);
+
+
+/**
+ * @brief Read a value from the buffer, return success.
+ *
+ * @param cb   : buffer
+ * @param dest : read destionation. If NULL, value is discarded.
+ * @return success
+ */
+bool cbuf_pop(CircBuf *cb, void *dest);
+
+
+/** @brief Remove all data from buffer */
+void cbuf_clear(CircBuf *cb);
+
+#endif // F103_USB_CIRCBUF_H
diff --git a/Inc/keyboard.h b/Inc/keyboard.h
new file mode 100644
index 0000000..31c7540
--- /dev/null
+++ b/Inc/keyboard.h
@@ -0,0 +1,339 @@
+//
+// Created by MightyPork on 7.8.16.
+//
+
+#ifndef F103_USB_KEYBOARD_H
+#define F103_USB_KEYBOARD_H
+
+#include <stdbool.h>
+#include <stdint.h>
+
+/** Max nr of simultaneous keys pressed */
+#define KYBD_SLOTS 6
+
+/** Struct that can be used for key buffers */
+typedef struct {
+	uint8_t key;
+	bool press;
+} KeyEvent;
+
+/**
+ * Toggle key state
+ *
+ * @param key : key code
+ * @param press : key pressed / released
+ */
+bool kybd_key(uint8_t key, bool press);
+
+/**
+ * Toggle modifier
+ *
+ * @param mod : Modifier mask
+ * @param press : Modifier pressed / released
+ */
+void kybd_mod(uint8_t mod, bool press);
+
+/**
+ * Press a key
+ *
+ * @param key : key code
+ */
+bool kybd_press(uint8_t key);
+
+/**
+ * Release a key
+ *
+ * @param key : key code
+ */
+bool kybd_release(uint8_t key);
+
+/**
+ * Release all keys and cancel all modifiers
+ */
+void kybd_clear();
+
+/**
+ * Get keyboard bytes for the USB HID report.
+ *
+ * @param arr : array long at least KYBD_SLOTS + 2
+ */
+void kybd_get_bytes(uint8_t *arr);
+
+/* ----------------------------------------------------------- */
+
+/**
+ * Modifier masks. Those may be used to directly set modifier status,
+ * as opposed to modifier Scan Codes 0xe0 - 0xe7, which do the same,
+ * but via the key press/release interface.
+ */
+#define MOD_LCTRL  0x01
+#define MOD_LSHIFT 0x02
+#define MOD_LALT   0x04
+#define MOD_LMETA  0x08
+#define MOD_RCTRL  0x10
+#define MOD_RSHIFT 0x20
+#define MOD_RALT   0x40
+#define MOD_RMETA  0x80
+
+/**
+ * USB HID Keyboard scan codes as per USB spec 1.11
+ * plus some additional codes
+ *
+ * Created by MightyPork, 2016
+ * Public domain
+ *
+ * Adapted from:
+ * https://source.android.com/devices/input/keyboard-devices.html
+ */
+#define KEY_NONE 0x00
+#define KEY_ERR_OVF 0x01 // Keyboard Error Roll Over - used for all slots if too many keys are pressed ("Phantom key")
+// 0x02 //  Keyboard POST Fail
+// 0x03 //  Keyboard Error Undefined
+#define KEY_A 0x04 // Keyboard a and A
+#define KEY_B 0x05 // Keyboard b and B
+#define KEY_C 0x06 // Keyboard c and C
+#define KEY_D 0x07 // Keyboard d and D
+#define KEY_E 0x08 // Keyboard e and E
+#define KEY_F 0x09 // Keyboard f and F
+#define KEY_G 0x0a // Keyboard g and G
+#define KEY_H 0x0b // Keyboard h and H
+#define KEY_I 0x0c // Keyboard i and I
+#define KEY_J 0x0d // Keyboard j and J
+#define KEY_K 0x0e // Keyboard k and K
+#define KEY_L 0x0f // Keyboard l and L
+#define KEY_M 0x10 // Keyboard m and M
+#define KEY_N 0x11 // Keyboard n and N
+#define KEY_O 0x12 // Keyboard o and O
+#define KEY_P 0x13 // Keyboard p and P
+#define KEY_Q 0x14 // Keyboard q and Q
+#define KEY_R 0x15 // Keyboard r and R
+#define KEY_S 0x16 // Keyboard s and S
+#define KEY_T 0x17 // Keyboard t and T
+#define KEY_U 0x18 // Keyboard u and U
+#define KEY_V 0x19 // Keyboard v and V
+#define KEY_W 0x1a // Keyboard w and W
+#define KEY_X 0x1b // Keyboard x and X
+#define KEY_Y 0x1c // Keyboard y and Y
+#define KEY_Z 0x1d // Keyboard z and Z
+
+#define KEY_1 0x1e // Keyboard 1 and !
+#define KEY_2 0x1f // Keyboard 2 and @
+#define KEY_3 0x20 // Keyboard 3 and #
+#define KEY_4 0x21 // Keyboard 4 and $
+#define KEY_5 0x22 // Keyboard 5 and %
+#define KEY_6 0x23 // Keyboard 6 and ^
+#define KEY_7 0x24 // Keyboard 7 and &
+#define KEY_8 0x25 // Keyboard 8 and *
+#define KEY_9 0x26 // Keyboard 9 and (
+#define KEY_0 0x27 // Keyboard 0 and )
+
+#define KEY_ENTER 0x28 // Keyboard Return (ENTER)
+#define KEY_ESC 0x29 // Keyboard ESCAPE
+#define KEY_BACKSPACE 0x2a // Keyboard DELETE (Backspace)
+#define KEY_TAB 0x2b // Keyboard Tab
+#define KEY_SPACE 0x2c // Keyboard Spacebar
+#define KEY_MINUS 0x2d // Keyboard - and _
+#define KEY_EQUAL 0x2e // Keyboard = and +
+#define KEY_LEFTBRACE 0x2f // Keyboard [ and {
+#define KEY_RIGHTBRACE 0x30 // Keyboard ] and }
+#define KEY_BACKSLASH 0x31 // Keyboard \ and |
+#define KEY_HASHTILDE 0x32 // Keyboard Non-US # and ~
+#define KEY_SEMICOLON 0x33 // Keyboard ; and :
+#define KEY_APOSTROPHE 0x34 // Keyboard ' and "
+#define KEY_GRAVE 0x35 // Keyboard ` and ~
+#define KEY_COMMA 0x36 // Keyboard , and <
+#define KEY_DOT 0x37 // Keyboard . and >
+#define KEY_SLASH 0x38 // Keyboard / and ?
+#define KEY_CAPSLOCK 0x39 // Keyboard Caps Lock
+
+#define KEY_F1 0x3a // Keyboard F1
+#define KEY_F2 0x3b // Keyboard F2
+#define KEY_F3 0x3c // Keyboard F3
+#define KEY_F4 0x3d // Keyboard F4
+#define KEY_F5 0x3e // Keyboard F5
+#define KEY_F6 0x3f // Keyboard F6
+#define KEY_F7 0x40 // Keyboard F7
+#define KEY_F8 0x41 // Keyboard F8
+#define KEY_F9 0x42 // Keyboard F9
+#define KEY_F10 0x43 // Keyboard F10
+#define KEY_F11 0x44 // Keyboard F11
+#define KEY_F12 0x45 // Keyboard F12
+
+#define KEY_SYSRQ 0x46 // Keyboard Print Screen
+#define KEY_SCROLLLOCK 0x47 // Keyboard Scroll Lock
+#define KEY_PAUSE 0x48 // Keyboard Pause
+#define KEY_INSERT 0x49 // Keyboard Insert
+#define KEY_HOME 0x4a // Keyboard Home
+#define KEY_PAGEUP 0x4b // Keyboard Page Up
+#define KEY_DELETE 0x4c // Keyboard Delete Forward
+#define KEY_END 0x4d // Keyboard End
+#define KEY_PAGEDOWN 0x4e // Keyboard Page Down
+#define KEY_RIGHT 0x4f // Keyboard Right Arrow
+#define KEY_LEFT 0x50 // Keyboard Left Arrow
+#define KEY_DOWN 0x51 // Keyboard Down Arrow
+#define KEY_UP 0x52 // Keyboard Up Arrow
+
+#define KEY_NUMLOCK 0x53 // Keyboard Num Lock and Clear
+#define KEY_KPSLASH 0x54 // Keypad /
+#define KEY_KPASTERISK 0x55 // Keypad *
+#define KEY_KPMINUS 0x56 // Keypad -
+#define KEY_KPPLUS 0x57 // Keypad +
+#define KEY_KPENTER 0x58 // Keypad ENTER
+#define KEY_KP1 0x59 // Keypad 1 and End
+#define KEY_KP2 0x5a // Keypad 2 and Down Arrow
+#define KEY_KP3 0x5b // Keypad 3 and PageDn
+#define KEY_KP4 0x5c // Keypad 4 and Left Arrow
+#define KEY_KP5 0x5d // Keypad 5
+#define KEY_KP6 0x5e // Keypad 6 and Right Arrow
+#define KEY_KP7 0x5f // Keypad 7 and Home
+#define KEY_KP8 0x60 // Keypad 8 and Up Arrow
+#define KEY_KP9 0x61 // Keypad 9 and Page Up
+#define KEY_KP0 0x62 // Keypad 0 and Insert
+#define KEY_KPDOT 0x63 // Keypad . and Delete
+
+#define KEY_102ND 0x64 // Keyboard Non-US \ and |
+#define KEY_COMPOSE 0x65 // Keyboard Application
+#define KEY_POWER 0x66 // Keyboard Power
+#define KEY_KPEQUAL 0x67 // Keypad =
+
+#define KEY_F13 0x68 // Keyboard F13
+#define KEY_F14 0x69 // Keyboard F14
+#define KEY_F15 0x6a // Keyboard F15
+#define KEY_F16 0x6b // Keyboard F16
+#define KEY_F17 0x6c // Keyboard F17
+#define KEY_F18 0x6d // Keyboard F18
+#define KEY_F19 0x6e // Keyboard F19
+#define KEY_F20 0x6f // Keyboard F20
+#define KEY_F21 0x70 // Keyboard F21
+#define KEY_F22 0x71 // Keyboard F22
+#define KEY_F23 0x72 // Keyboard F23
+#define KEY_F24 0x73 // Keyboard F24
+
+#define KEY_OPEN 0x74 // Keyboard Execute
+#define KEY_HELP 0x75 // Keyboard Help
+#define KEY_PROPS 0x76 // Keyboard Menu
+#define KEY_FRONT 0x77 // Keyboard Select
+#define KEY_STOP 0x78 // Keyboard Stop
+#define KEY_AGAIN 0x79 // Keyboard Again
+#define KEY_UNDO 0x7a // Keyboard Undo
+#define KEY_CUT 0x7b // Keyboard Cut
+#define KEY_COPY 0x7c // Keyboard Copy
+#define KEY_PASTE 0x7d // Keyboard Paste
+#define KEY_FIND 0x7e // Keyboard Find
+#define KEY_MUTE 0x7f // Keyboard Mute
+#define KEY_VOLUMEUP 0x80 // Keyboard Volume Up
+#define KEY_VOLUMEDOWN 0x81 // Keyboard Volume Down
+// 0x82  Keyboard Locking Caps Lock
+// 0x83  Keyboard Locking Num Lock
+// 0x84  Keyboard Locking Scroll Lock
+#define KEY_KPCOMMA 0x85 // Keypad Comma
+// 0x86  Keypad Equal Sign
+#define KEY_RO 0x87 // Keyboard International1
+#define KEY_KATAKANAHIRAGANA 0x88 // Keyboard International2
+#define KEY_YEN 0x89 // Keyboard International3
+#define KEY_HENKAN 0x8a // Keyboard International4
+#define KEY_MUHENKAN 0x8b // Keyboard International5
+#define KEY_KPJPCOMMA 0x8c // Keyboard International6
+// 0x8d  Keyboard International7
+// 0x8e  Keyboard International8
+// 0x8f  Keyboard International9
+#define KEY_HANGEUL 0x90 // Keyboard LANG1
+#define KEY_HANJA 0x91 // Keyboard LANG2
+#define KEY_KATAKANA 0x92 // Keyboard LANG3
+#define KEY_HIRAGANA 0x93 // Keyboard LANG4
+#define KEY_ZENKAKUHANKAKU 0x94 // Keyboard LANG5
+// 0x95  Keyboard LANG6
+// 0x96  Keyboard LANG7
+// 0x97  Keyboard LANG8
+// 0x98  Keyboard LANG9
+// 0x99  Keyboard Alternate Erase
+// 0x9a  Keyboard SysReq/Attention
+// 0x9b  Keyboard Cancel
+// 0x9c  Keyboard Clear
+// 0x9d  Keyboard Prior
+// 0x9e  Keyboard Return
+// 0x9f  Keyboard Separator
+// 0xa0  Keyboard Out
+// 0xa1  Keyboard Oper
+// 0xa2  Keyboard Clear/Again
+// 0xa3  Keyboard CrSel/Props
+// 0xa4  Keyboard ExSel
+
+// 0xb0  Keypad 00
+// 0xb1  Keypad 000
+// 0xb2  Thousands Separator
+// 0xb3  Decimal Separator
+// 0xb4  Currency Unit
+// 0xb5  Currency Sub-unit
+#define KEY_KPLEFTPAREN 0xb6 // Keypad (
+#define KEY_KPRIGHTPAREN 0xb7 // Keypad )
+// 0xb8  Keypad {
+// 0xb9  Keypad }
+// 0xba  Keypad Tab
+// 0xbb  Keypad Backspace
+// 0xbc  Keypad A
+// 0xbd  Keypad B
+// 0xbe  Keypad C
+// 0xbf  Keypad D
+// 0xc0  Keypad E
+// 0xc1  Keypad F
+// 0xc2  Keypad XOR
+// 0xc3  Keypad ^
+// 0xc4  Keypad %
+// 0xc5  Keypad <
+// 0xc6  Keypad >
+// 0xc7  Keypad &
+// 0xc8  Keypad &&
+// 0xc9  Keypad |
+// 0xca  Keypad ||
+// 0xcb  Keypad :
+// 0xcc  Keypad #
+// 0xcd  Keypad Space
+// 0xce  Keypad @
+// 0xcf  Keypad !
+// 0xd0  Keypad Memory Store
+// 0xd1  Keypad Memory Recall
+// 0xd2  Keypad Memory Clear
+// 0xd3  Keypad Memory Add
+// 0xd4  Keypad Memory Subtract
+// 0xd5  Keypad Memory Multiply
+// 0xd6  Keypad Memory Divide
+// 0xd7  Keypad +/-
+// 0xd8  Keypad Clear
+// 0xd9  Keypad Clear Entry
+// 0xda  Keypad Binary
+// 0xdb  Keypad Octal
+// 0xdc  Keypad Decimal
+// 0xdd  Keypad Hexadecimal
+
+#define KEY_LEFTCTRL 0xe0 // Keyboard Left Control
+#define KEY_LEFTSHIFT 0xe1 // Keyboard Left Shift
+#define KEY_LEFTALT 0xe2 // Keyboard Left Alt
+#define KEY_LEFTMETA 0xe3 // Keyboard Left GUI
+#define KEY_RIGHTCTRL 0xe4 // Keyboard Right Control
+#define KEY_RIGHTSHIFT 0xe5 // Keyboard Right Shift
+#define KEY_RIGHTALT 0xe6 // Keyboard Right Alt
+#define KEY_RIGHTMETA 0xe7 // Keyboard Right GUI
+
+#define KEY_MEDIA_PLAYPAUSE 0xe8
+#define KEY_MEDIA_STOPCD 0xe9
+#define KEY_MEDIA_PREVIOUSSONG 0xea
+#define KEY_MEDIA_NEXTSONG 0xeb
+#define KEY_MEDIA_EJECTCD 0xec
+#define KEY_MEDIA_VOLUMEUP 0xed
+#define KEY_MEDIA_VOLUMEDOWN 0xee
+#define KEY_MEDIA_MUTE 0xef
+#define KEY_MEDIA_WWW 0xf0
+#define KEY_MEDIA_BACK 0xf1
+#define KEY_MEDIA_FORWARD 0xf2
+#define KEY_MEDIA_STOP 0xf3
+#define KEY_MEDIA_FIND 0xf4
+#define KEY_MEDIA_SCROLLUP 0xf5
+#define KEY_MEDIA_SCROLLDOWN 0xf6
+#define KEY_MEDIA_EDIT 0xf7
+#define KEY_MEDIA_SLEEP 0xf8
+#define KEY_MEDIA_COFFEE 0xf9
+#define KEY_MEDIA_REFRESH 0xfa
+#define KEY_MEDIA_CALC 0xfb
+
+#endif //F103_USB_KEYBOARD_H
diff --git a/Inc/main.h b/Inc/main.h
index e3a3633..4b26812 100644
--- a/Inc/main.h
+++ b/Inc/main.h
@@ -6,7 +6,10 @@
 #define F103_USB_MAIN_H_H
 
 #include "stm32f1xx_hal.h"
+#include "circbuf.h"
 
 extern void dbg(const char* msg);
 
+extern CircBuf *key_cbuf;
+
 #endif //F103_USB_MAIN_H_H
diff --git a/Middlewares/ST/STM32_USB_Device_Library/Class/HID/Inc/usbd_hid.h b/Middlewares/ST/STM32_USB_Device_Library/Class/HID/Inc/usbd_hid.h
index a46b8f3..14577a1 100644
--- a/Middlewares/ST/STM32_USB_Device_Library/Class/HID/Inc/usbd_hid.h
+++ b/Middlewares/ST/STM32_USB_Device_Library/Class/HID/Inc/usbd_hid.h
@@ -50,7 +50,8 @@ extern "C" {
   * @{
   */
 #define HID_EPIN_ADDR                 0x81
-#define HID_EPIN_SIZE                 0x04
+// CHANGED
+#define HID_EPIN_SIZE                 0x08
 
 #define USB_HID_CONFIG_DESC_SIZ       34
 #define USB_HID_DESC_SIZ              9
diff --git a/Middlewares/ST/STM32_USB_Device_Library/Class/HID/Src/usbd_hid.c b/Middlewares/ST/STM32_USB_Device_Library/Class/HID/Src/usbd_hid.c
index 6f54f66..562dc7e 100644
--- a/Middlewares/ST/STM32_USB_Device_Library/Class/HID/Src/usbd_hid.c
+++ b/Middlewares/ST/STM32_USB_Device_Library/Class/HID/Src/usbd_hid.c
@@ -166,7 +166,7 @@ __ALIGN_BEGIN static uint8_t USBD_HID_CfgDesc[USB_HID_CONFIG_DESC_SIZ]  __ALIGN_
 				0x01,         /*bInterfaceSubClass : 1=BOOT, 0=no boot*/
 				0x01,         /*nInterfaceProtocol : 0=none, 1=keyboard, 2=mouse*//* CHANGED */
 				0,            /*iInterface: Index of string descriptor*/
-				/******************** Descriptor of Joystick Mouse HID ********************/
+				/******************** Descriptor of Keyboard HID ********************/
 				/* 18 */
 				0x09,         /*bLength: HID Descriptor size*/
 				HID_DESCRIPTOR_TYPE, /*bDescriptorType: HID*/
@@ -191,6 +191,7 @@ __ALIGN_BEGIN static uint8_t USBD_HID_CfgDesc[USB_HID_CONFIG_DESC_SIZ]  __ALIGN_
 		};
 
 /* USB HID device Configuration Descriptor */
+/* SAME AS ABOVE! */
 __ALIGN_BEGIN static uint8_t USBD_HID_Desc[USB_HID_DESC_SIZ]  __ALIGN_END =
 		{
 				/* 18 */
@@ -225,7 +226,10 @@ __ALIGN_BEGIN static uint8_t HID_KEYBD_ReportDesc[HID_KEYBD_REPORT_DESC_SIZE]  _
 				0x05, 0x01,                    // USAGE_PAGE (Generic Desktop)
 				0x09, 0x06,                    // USAGE (Keyboard)
 				0xa1, 0x01,                    // COLLECTION (Application)
+
 				0x05, 0x07,                    //   USAGE_PAGE (Keyboard)
+
+				// Modifier byte - 8 bits
 				0x19, 0xe0,                    //   USAGE_MINIMUM (Keyboard LeftControl)
 				0x29, 0xe7,                    //   USAGE_MAXIMUM (Keyboard Right GUI)
 				0x15, 0x00,                    //   LOGICAL_MINIMUM (0)
@@ -233,26 +237,34 @@ __ALIGN_BEGIN static uint8_t HID_KEYBD_ReportDesc[HID_KEYBD_REPORT_DESC_SIZE]  _
 				0x75, 0x01,                    //   REPORT_SIZE (1)
 				0x95, 0x08,                    //   REPORT_COUNT (8)
 				0x81, 0x02,                    //   INPUT (Data,Var,Abs)
+
+				// reserved byte - 8 bits
 				0x95, 0x01,                    //   REPORT_COUNT (1)
 				0x75, 0x08,                    //   REPORT_SIZE (8)
 				0x81, 0x03,                    //   INPUT (Cnst,Var,Abs)
+
+				// LEDs report - 5 bits
 				0x95, 0x05,                    //   REPORT_COUNT (5)
 				0x75, 0x01,                    //   REPORT_SIZE (1)
 				0x05, 0x08,                    //   USAGE_PAGE (LEDs)
 				0x19, 0x01,                    //   USAGE_MINIMUM (Num Lock)
 				0x29, 0x05,                    //   USAGE_MAXIMUM (Kana)
 				0x91, 0x02,                    //   OUTPUT (Data,Var,Abs)
+				// Unused padding - 3 bits
 				0x95, 0x01,                    //   REPORT_COUNT (1)
 				0x75, 0x03,                    //   REPORT_SIZE (3)
-				0x91, 0x03,                    //   OUTPUT (Cnst,Var,Abs)
+				0x91, 0x03,                    //   OUTPUT (Cnst,Var,Abs) - padding, unused
+
+				// Key codes - 6 bytes
 				0x95, 0x06,                    //   REPORT_COUNT (6)
 				0x75, 0x08,                    //   REPORT_SIZE (8)
 				0x15, 0x00,                    //   LOGICAL_MINIMUM (0)
 				0x25, 0x65,                    //   LOGICAL_MAXIMUM (101)
 				0x05, 0x07,                    //   USAGE_PAGE (Keyboard)
 				0x19, 0x00,                    //   USAGE_MINIMUM (Reserved (no event indicated))
-				0x29, 0x65,                    //   USAGE_MAXIMUM (Keyboard Application)
+				0x29, 0x65,                    //   USAGE_MAXIMUM (Keyboard Application) - Key down
 				0x81, 0x00,                    //   INPUT (Data,Ary,Abs)
+
 				0xc0                           // END_COLLECTION
 		};
 
diff --git a/Src/circbuf.c b/Src/circbuf.c
new file mode 100644
index 0000000..3c2a232
--- /dev/null
+++ b/Src/circbuf.c
@@ -0,0 +1,163 @@
+#include <stdint.h>
+#include <stdbool.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "circbuf.h"
+
+#define malloc_s malloc
+
+// --- Circbuf data structure ----
+
+/** Offset in void* buffer */
+#define PV_OFFS(pvBuf, elem_size, index) ((uint8_t*)(pvBuf) + ((elem_size)*(index)))
+
+
+// Instance structure
+struct circbuf_struct {
+	void *buf;
+	size_t elem_size;
+	size_t cap;
+	size_t lr; // last read pos
+	size_t nw; // next write pos
+};
+
+
+/**
+ * @brief Write data to a CircBuf slot
+ * @param cb     : circbuf
+ * @param index  : slot index
+ * @param source : data source
+ */
+static void write_buffer(CircBuf *cb, size_t index, const void *source)
+{
+	memcpy(PV_OFFS(cb->buf, cb->elem_size, index), source, cb->elem_size);
+}
+
+
+/**
+ * @brief Copy data from a CircBuf slot to a buffer
+ * @param cb     : circbuf
+ * @param index  : slot index
+ * @param dest   : destination buffer
+ */
+static void read_buffer(const CircBuf *cb, size_t index, void *dest)
+{
+	memcpy(dest, PV_OFFS(cb->buf, cb->elem_size, index), cb->elem_size);
+}
+
+
+/** Create a cbuf */
+CircBuf *cbuf_create(size_t capacity, size_t elem_size)
+{
+	// add one, because one is always unused.
+	capacity++;
+
+	// Allocate the structure
+	CircBuf *cb = malloc_s(sizeof(CircBuf));
+
+	// allocate the buffer
+	cb->buf = malloc_s(capacity * elem_size);
+
+	// set capacity, clear state
+	cb->elem_size = elem_size;
+	cb->cap = capacity;
+	cbuf_clear(cb);
+
+	return cb;
+}
+
+
+/** Release cbuf memory */
+void cbuf_destroy(CircBuf *cb)
+{
+	if (cb != NULL) {
+		if (cb->buf != NULL) {
+			free(cb->buf);
+		}
+
+		free(cb);
+	}
+}
+
+
+/** Check if cbuf is full */
+bool cbuf_full(const CircBuf *cb)
+{
+	if (cb == NULL) return false;
+
+	return (cb->lr == cb->nw);
+}
+
+
+/** Check if cbuf is empty */
+bool cbuf_empty(const CircBuf *cb)
+{
+	if (cb == NULL) return true;
+
+	return ((cb->lr + 1) % cb->cap) == cb->nw;
+}
+
+
+/** Write a byte to the buffer, if space left */
+bool cbuf_append(CircBuf *cb, const void *source)
+{
+	if (cb == NULL) return false;
+	if (source == NULL) return false;
+	if (cbuf_full(cb)) return false;
+
+	write_buffer(cb, cb->nw, source);
+
+	// increment
+	cb->nw++;
+	if (cb->nw == cb->cap) cb->nw = 0;
+
+	return true;
+}
+
+
+/** Push value to the end, like a stack. */
+bool cbuf_push(CircBuf *cb, const void *source)
+{
+	if (cb == NULL) return false;
+	if (source == NULL) return false;
+	if (cbuf_full(cb)) return false;
+
+	write_buffer(cb, cb->lr, source);
+
+	// move lr back
+	if (cb->lr == 0) {
+		cb->lr = cb->cap - 1; // wrap to the end
+	} else {
+		cb->lr--;
+	}
+
+	return true;
+}
+
+
+/** Read one byte, if not empty. */
+bool cbuf_pop(CircBuf *cb, void *dest)
+{
+	if (cb == NULL || dest == NULL) return false;
+	if (cbuf_empty(cb)) return false;
+
+	// increment
+	cb->lr++;
+	if (cb->lr == cb->cap) cb->lr = 0;
+
+	read_buffer(cb, cb->lr, dest);
+
+	return true;
+}
+
+
+/** Clear a cbuf */
+void cbuf_clear(CircBuf *cb)
+{
+	if (cb == NULL) return;
+
+	cb->lr = cb->cap - 1;
+	cb->nw = 0;
+}
diff --git a/Src/keyboard.c b/Src/keyboard.c
new file mode 100644
index 0000000..eda46a2
--- /dev/null
+++ b/Src/keyboard.c
@@ -0,0 +1,117 @@
+//
+// Created by MightyPork on 7.8.16.
+//
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <string.h>
+#include "keyboard.h"
+
+static uint8_t modifiers = 0x00;
+
+static uint8_t keys[KYBD_SLOTS] = {};
+
+static uint8_t free_slot = 0;
+
+static bool err_ovf = false;
+
+/** Clear keys and mods */
+void kybd_clear() {
+	memset(keys, 0x00, KYBD_SLOTS);
+	modifiers = 0x00;
+	free_slot = 0;
+	err_ovf = false;
+}
+
+/** Key down */
+bool kybd_press(uint8_t key) {
+	kybd_key(key, true);
+}
+
+/** Key up */
+bool kybd_release(uint8_t key) {
+	kybd_key(key, false);
+}
+
+/** Modifier press or release */
+void kybd_mod(uint8_t mod, bool press) {
+	if (press) {
+		modifiers |= mod;
+	} else {
+		modifiers &= ~mod;
+	}
+}
+
+/** Key press or release */
+bool kybd_key(uint8_t key, bool press) {
+	if (key >= KEY_LEFTCTRL && key <= KEY_RIGHTMETA) {
+		// Modifier key
+
+		// conveniently, the lower byte indicates the modifier position
+		uint8_t bitshift = (uint8_t) (key & 0x0F);
+		// obtain the modifier mask
+		uint8_t mod = (uint8_t) (1 << bitshift);
+		// apply modifier
+		kybd_mod(mod, press);
+
+		goto suc;
+	}
+
+	// Regular key
+	if (press) {
+		for (int i = 0; i < KYBD_SLOTS; i++) {
+			if (keys[i] == key) {
+				// key is already pressed
+				goto suc;
+			}
+		}
+
+		if (free_slot < KYBD_SLOTS) {
+			// press the key
+			keys[free_slot++] = key;
+			goto suc;
+		}
+
+		err_ovf = true; // set overflow flag
+	}
+	else {
+		// release
+		bool found = false;
+		for (int i = 0; i < KYBD_SLOTS; i++) {
+			if (found) {
+				keys[i - 1] = keys[i];
+				if (i == KYBD_SLOTS - 1) {
+					keys[i] = 0x00;
+				}
+			}
+			else {
+				if (keys[i] == key) {
+					found = true;
+				}
+			}
+		}
+		if (found) {
+			err_ovf = false; // clear overflow flag
+			free_slot--;
+			goto suc;
+		}
+	}
+
+	return false;
+suc:
+	return true;
+}
+
+/** Get HID report */
+void kybd_get_bytes(uint8_t *arr) {
+	arr[0] = modifiers;
+	arr[1] = 0x00;
+
+	if (err_ovf) {
+		// all slots ERR_OVF
+		memset(arr + 2, KEY_ERR_OVF, KYBD_SLOTS);
+	} else {
+		// show keys
+		memcpy(arr + 2, keys, KYBD_SLOTS);
+	}
+}
diff --git a/Src/main.c b/Src/main.c
index 378fbcc..d9f1d01 100644
--- a/Src/main.c
+++ b/Src/main.c
@@ -31,6 +31,10 @@
   ******************************************************************************
   */
 /* Includes ------------------------------------------------------------------*/
+#include <usbd_hid.h>
+#include <stdbool.h>
+#include <keyboard.h>
+#include <circbuf.h>
 #include "stm32f1xx_hal.h"
 #include "usart.h"
 #include "usb_device.h"
@@ -59,27 +63,68 @@ void Error_Handler(void);
 
 /* USER CODE BEGIN 0 */
 
+CircBuf *key_cbuf;
+
+
+void fkey_press(uint8_t key) {
+	KeyEvent ke = {key, true};
+	cbuf_append(key_cbuf, &ke);
+}
+
+void fkey_release(uint8_t key) {
+	KeyEvent ke = {key, false};
+	cbuf_append(key_cbuf, &ke);
+}
+
+void fkey_type(uint8_t key, bool shift) {
+	if(shift) fkey_press(KEY_LEFTSHIFT);
+	fkey_press(key);
+	fkey_release(key);
+	if(shift) fkey_release(KEY_LEFTSHIFT);
+}
+
+
 /** Print a debug message */
-void dbg(const char *msg)
-{
+void dbg(const char *msg) {
 	HAL_UART_Transmit(&huart2, (char *) msg, (uint16_t) strlen(msg), 10);
 }
 
 
-void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin)
-{
+void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin) {
 	UNUSED(GPIO_Pin);
 
+	static uint32_t lasttick = 0;
+
 	dbg("EXTI!\r\n");
-}
 
+	if (HAL_GetTick() - lasttick < 1000) {
+		dbg("Discard, too soon\r\n");
+		return;
+	}
 
-/* USER CODE END 0 */
+	dbg("HEYOOO\r\n");
+
+	fkey_type(KEY_H, true);
+	fkey_type(KEY_E, false);
+	fkey_type(KEY_L, false);
+	fkey_type(KEY_L, false);
+	fkey_type(KEY_O, false);
+	fkey_type(KEY_SPACE, false);
+	fkey_type(KEY_W, true);
+	fkey_type(KEY_O, false);
+	fkey_type(KEY_R, false);
+	fkey_type(KEY_L, false);
+	fkey_type(KEY_D, false);
+	fkey_type(KEY_ENTER, false);
+}
 
-int main(void)
-{
+/* USER CODE END 0 */
 
+int main(void) {
 	/* USER CODE BEGIN 1 */
+	kybd_clear();
+
+	key_cbuf = cbuf_create(100, sizeof(KeyEvent));
 
 	/* USER CODE END 1 */
 
@@ -105,6 +150,8 @@ int main(void)
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wmissing-noreturn"
 
+	dbg("-- READY! --\r\n\r\n");
+
 	char msg[] = "A\r\n";
 
 	while (1) {
@@ -132,8 +179,7 @@ int main(void)
 
 /** System Clock Configuration
 */
-void SystemClock_Config(void)
-{
+void SystemClock_Config(void) {
 
 	RCC_OscInitTypeDef RCC_OscInitStruct;
 	RCC_ClkInitTypeDef RCC_ClkInitStruct;
@@ -182,8 +228,7 @@ void SystemClock_Config(void)
   * @param  None
   * @retval None
   */
-void Error_Handler(void)
-{
+void Error_Handler(void) {
 	/* USER CODE BEGIN Error_Handler */
 	/* User can add his own implementation to report the HAL error return state */
 	while (1) {
diff --git a/Src/stm32f1xx_it.c b/Src/stm32f1xx_it.c
index 841a92f..222a743 100644
--- a/Src/stm32f1xx_it.c
+++ b/Src/stm32f1xx_it.c
@@ -31,9 +31,14 @@
   ******************************************************************************
   */
 /* Includes ------------------------------------------------------------------*/
+#include <main.h>
+#include <keyboard.h>
+#include <usb_device.h>
+#include <usbd_hid.h>
 #include "stm32f1xx_hal.h"
 #include "stm32f1xx.h"
 #include "stm32f1xx_it.h"
+#include "circbuf.h"
 
 /* USER CODE BEGIN 0 */
 
@@ -43,138 +48,139 @@
 extern PCD_HandleTypeDef hpcd_USB_FS;
 
 /******************************************************************************/
-/*            Cortex-M3 Processor Interruption and Exception Handlers         */ 
+/*            Cortex-M3 Processor Interruption and Exception Handlers         */
 /******************************************************************************/
 
 /**
 * @brief This function handles Non maskable interrupt.
 */
-void NMI_Handler(void)
-{
-  /* USER CODE BEGIN NonMaskableInt_IRQn 0 */
+void NMI_Handler(void) {
+	/* USER CODE BEGIN NonMaskableInt_IRQn 0 */
 
-  /* USER CODE END NonMaskableInt_IRQn 0 */
-  /* USER CODE BEGIN NonMaskableInt_IRQn 1 */
+	/* USER CODE END NonMaskableInt_IRQn 0 */
+	/* USER CODE BEGIN NonMaskableInt_IRQn 1 */
 
-  /* USER CODE END NonMaskableInt_IRQn 1 */
+	/* USER CODE END NonMaskableInt_IRQn 1 */
 }
 
 /**
 * @brief This function handles Hard fault interrupt.
 */
-void HardFault_Handler(void)
-{
-  /* USER CODE BEGIN HardFault_IRQn 0 */
+void HardFault_Handler(void) {
+	/* USER CODE BEGIN HardFault_IRQn 0 */
 
-  /* USER CODE END HardFault_IRQn 0 */
-  while (1)
-  {
-  }
-  /* USER CODE BEGIN HardFault_IRQn 1 */
+	/* USER CODE END HardFault_IRQn 0 */
+	while (1) {
+	}
+	/* USER CODE BEGIN HardFault_IRQn 1 */
 
-  /* USER CODE END HardFault_IRQn 1 */
+	/* USER CODE END HardFault_IRQn 1 */
 }
 
 /**
 * @brief This function handles Memory management fault.
 */
-void MemManage_Handler(void)
-{
-  /* USER CODE BEGIN MemoryManagement_IRQn 0 */
+void MemManage_Handler(void) {
+	/* USER CODE BEGIN MemoryManagement_IRQn 0 */
 
-  /* USER CODE END MemoryManagement_IRQn 0 */
-  while (1)
-  {
-  }
-  /* USER CODE BEGIN MemoryManagement_IRQn 1 */
+	/* USER CODE END MemoryManagement_IRQn 0 */
+	while (1) {
+	}
+	/* USER CODE BEGIN MemoryManagement_IRQn 1 */
 
-  /* USER CODE END MemoryManagement_IRQn 1 */
+	/* USER CODE END MemoryManagement_IRQn 1 */
 }
 
 /**
 * @brief This function handles Prefetch fault, memory access fault.
 */
-void BusFault_Handler(void)
-{
-  /* USER CODE BEGIN BusFault_IRQn 0 */
+void BusFault_Handler(void) {
+	/* USER CODE BEGIN BusFault_IRQn 0 */
 
-  /* USER CODE END BusFault_IRQn 0 */
-  while (1)
-  {
-  }
-  /* USER CODE BEGIN BusFault_IRQn 1 */
+	/* USER CODE END BusFault_IRQn 0 */
+	while (1) {
+	}
+	/* USER CODE BEGIN BusFault_IRQn 1 */
 
-  /* USER CODE END BusFault_IRQn 1 */
+	/* USER CODE END BusFault_IRQn 1 */
 }
 
 /**
 * @brief This function handles Undefined instruction or illegal state.
 */
-void UsageFault_Handler(void)
-{
-  /* USER CODE BEGIN UsageFault_IRQn 0 */
+void UsageFault_Handler(void) {
+	/* USER CODE BEGIN UsageFault_IRQn 0 */
 
-  /* USER CODE END UsageFault_IRQn 0 */
-  while (1)
-  {
-  }
-  /* USER CODE BEGIN UsageFault_IRQn 1 */
+	/* USER CODE END UsageFault_IRQn 0 */
+	while (1) {
+	}
+	/* USER CODE BEGIN UsageFault_IRQn 1 */
 
-  /* USER CODE END UsageFault_IRQn 1 */
+	/* USER CODE END UsageFault_IRQn 1 */
 }
 
 /**
 * @brief This function handles System service call via SWI instruction.
 */
-void SVC_Handler(void)
-{
-  /* USER CODE BEGIN SVCall_IRQn 0 */
+void SVC_Handler(void) {
+	/* USER CODE BEGIN SVCall_IRQn 0 */
 
-  /* USER CODE END SVCall_IRQn 0 */
-  /* USER CODE BEGIN SVCall_IRQn 1 */
+	/* USER CODE END SVCall_IRQn 0 */
+	/* USER CODE BEGIN SVCall_IRQn 1 */
 
-  /* USER CODE END SVCall_IRQn 1 */
+	/* USER CODE END SVCall_IRQn 1 */
 }
 
 /**
 * @brief This function handles Debug monitor.
 */
-void DebugMon_Handler(void)
-{
-  /* USER CODE BEGIN DebugMonitor_IRQn 0 */
+void DebugMon_Handler(void) {
+	/* USER CODE BEGIN DebugMonitor_IRQn 0 */
 
-  /* USER CODE END DebugMonitor_IRQn 0 */
-  /* USER CODE BEGIN DebugMonitor_IRQn 1 */
+	/* USER CODE END DebugMonitor_IRQn 0 */
+	/* USER CODE BEGIN DebugMonitor_IRQn 1 */
 
-  /* USER CODE END DebugMonitor_IRQn 1 */
+	/* USER CODE END DebugMonitor_IRQn 1 */
 }
 
 /**
 * @brief This function handles Pendable request for system service.
 */
-void PendSV_Handler(void)
-{
-  /* USER CODE BEGIN PendSV_IRQn 0 */
+void PendSV_Handler(void) {
+	/* USER CODE BEGIN PendSV_IRQn 0 */
 
-  /* USER CODE END PendSV_IRQn 0 */
-  /* USER CODE BEGIN PendSV_IRQn 1 */
+	/* USER CODE END PendSV_IRQn 0 */
+	/* USER CODE BEGIN PendSV_IRQn 1 */
 
-  /* USER CODE END PendSV_IRQn 1 */
+	/* USER CODE END PendSV_IRQn 1 */
 }
 
 /**
 * @brief This function handles System tick timer.
 */
-void SysTick_Handler(void)
-{
-  /* USER CODE BEGIN SysTick_IRQn 0 */
+void SysTick_Handler(void) {
+	/* USER CODE BEGIN SysTick_IRQn 0 */
+	static uint8_t kreport[8];
 
-  /* USER CODE END SysTick_IRQn 0 */
-  HAL_IncTick();
-  HAL_SYSTICK_IRQHandler();
-  /* USER CODE BEGIN SysTick_IRQn 1 */
+	/* USER CODE END SysTick_IRQn 0 */
+	HAL_IncTick();
+	HAL_SYSTICK_IRQHandler();
+	/* USER CODE BEGIN SysTick_IRQn 1 */
 
-  /* USER CODE END SysTick_IRQn 1 */
+	if (((USBD_HID_HandleTypeDef *) hUsbDeviceFS.pClassData)->state == HID_IDLE) {
+		KeyEvent ke;
+		if (cbuf_pop(key_cbuf, &ke)) {
+			kybd_key(ke.key, ke.press);
+
+			// Send report
+			dbg("key event\r\n");
+
+			kybd_get_bytes(kreport);
+			USBD_HID_SendReport(&hUsbDeviceFS, kreport, 8);
+		}
+	}
+
+	/* USER CODE END SysTick_IRQn 1 */
 }
 
 /******************************************************************************/
@@ -187,22 +193,20 @@ void SysTick_Handler(void)
 /**
 * @brief This function handles USB low priority or CAN RX0 interrupts.
 */
-void USB_LP_CAN1_RX0_IRQHandler(void)
-{
-  /* USER CODE BEGIN USB_LP_CAN1_RX0_IRQn 0 */
+void USB_LP_CAN1_RX0_IRQHandler(void) {
+	/* USER CODE BEGIN USB_LP_CAN1_RX0_IRQn 0 */
 
-  /* USER CODE END USB_LP_CAN1_RX0_IRQn 0 */
-  HAL_PCD_IRQHandler(&hpcd_USB_FS);
-  /* USER CODE BEGIN USB_LP_CAN1_RX0_IRQn 1 */
+	/* USER CODE END USB_LP_CAN1_RX0_IRQn 0 */
+	HAL_PCD_IRQHandler(&hpcd_USB_FS);
+	/* USER CODE BEGIN USB_LP_CAN1_RX0_IRQn 1 */
 
-  /* USER CODE END USB_LP_CAN1_RX0_IRQn 1 */
+	/* USER CODE END USB_LP_CAN1_RX0_IRQn 1 */
 }
 
 /* USER CODE BEGIN 1 */
 
-void EXTI1_IRQHandler(void)
-{
-  HAL_GPIO_EXTI_IRQHandler(GPIO_PIN_1);
+void EXTI1_IRQHandler(void) {
+	HAL_GPIO_EXTI_IRQHandler(GPIO_PIN_1);
 }
 
 /* USER CODE END 1 */
diff --git a/Src/syscalls.c b/Src/syscalls.c
new file mode 100644
index 0000000..72cb6be
--- /dev/null
+++ b/Src/syscalls.c
@@ -0,0 +1,32 @@
+#include <errno.h>
+#include <stdio.h>
+
+register char * stack_ptr asm("sp");
+
+caddr_t _sbrk(int incr)
+{
+	extern char end __asm("end");
+	static char *heap_end;
+	char *prev_heap_end;
+
+	if (heap_end == 0)
+		heap_end = &end;
+
+	prev_heap_end = heap_end;
+	if (heap_end + incr > stack_ptr)
+	{
+//		write(1, "Heap and stack collision\n", 25);
+//		abort();
+		errno = ENOMEM;
+		return (caddr_t) -1;
+	}
+
+	heap_end += incr;
+
+	return (caddr_t) prev_heap_end;
+}
+
+
+// Other systcalls are defined in
+// - com/com_fileio.c
+// - hw_utils/reset.h