diff --git a/CMakeLists.txt b/CMakeLists.txt
index 39e62fc..990a654 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -38,11 +38,14 @@ target_sources(app PRIVATE
   src/events/bat_state_event.c
   src/events/ble_serial_rx_event.c
   src/events/ble_serial_tx_event.c
+  src/events/cdc_proto_tx_event.c
   src/events/encoder_event.c
+  src/events/function_bitmap_update_event.c
   src/events/hid_led_event.c
   src/events/hid_report_sent_event.c
   src/events/hid_transport_state_event.c
   src/events/hid_tx_report_event.c
+  src/events/key_function_event.c
   src/mode_switch_module.c
   src/events/keyboard_hid_report_event.c
   src/events/mode_switch_event.c
diff --git a/inc/events/cdc_proto_tx_event.h b/inc/events/cdc_proto_tx_event.h
new file mode 100644
index 0000000..55a33b7
--- /dev/null
+++ b/inc/events/cdc_proto_tx_event.h
@@ -0,0 +1,23 @@
+#ifndef BLINKY_CDC_PROTO_TX_EVENT_H_
+#define BLINKY_CDC_PROTO_TX_EVENT_H_
+
+#include <app_event_manager.h>
+#include <app_event_manager_profiler_tracer.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct cdc_proto_tx_event {
+	struct app_event_header header;
+	uint8_t type;
+	struct event_dyndata dyndata;
+};
+
+APP_EVENT_TYPE_DYNDATA_DECLARE(cdc_proto_tx_event);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* BLINKY_CDC_PROTO_TX_EVENT_H_ */
diff --git a/inc/events/function_bitmap_update_event.h b/inc/events/function_bitmap_update_event.h
new file mode 100644
index 0000000..9e8277a
--- /dev/null
+++ b/inc/events/function_bitmap_update_event.h
@@ -0,0 +1,24 @@
+#ifndef BLINKY_FUNCTION_BITMAP_UPDATE_EVENT_H_
+#define BLINKY_FUNCTION_BITMAP_UPDATE_EVENT_H_
+
+#include <app_event_manager.h>
+#include <app_event_manager_profiler_tracer.h>
+
+#include "keyboard_core.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct function_bitmap_update_event {
+	struct app_event_header header;
+	uint8_t bitmap[KEYBOARD_PROTOCOL_BITMAP_BYTES];
+};
+
+APP_EVENT_TYPE_DECLARE(function_bitmap_update_event);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* BLINKY_FUNCTION_BITMAP_UPDATE_EVENT_H_ */
diff --git a/inc/events/key_function_event.h b/inc/events/key_function_event.h
new file mode 100644
index 0000000..6e67678
--- /dev/null
+++ b/inc/events/key_function_event.h
@@ -0,0 +1,28 @@
+#ifndef BLINKY_KEY_FUNCTION_EVENT_H_
+#define BLINKY_KEY_FUNCTION_EVENT_H_
+
+#include <app_event_manager.h>
+#include <app_event_manager_profiler_tracer.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+enum key_function_action {
+	KEY_FUNCTION_ACTION_RELEASE = 0U,
+	KEY_FUNCTION_ACTION_PRESS = 1U,
+};
+
+struct key_function_event {
+	struct app_event_header header;
+	uint16_t usage;
+	uint8_t action;
+};
+
+APP_EVENT_TYPE_DECLARE(key_function_event);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* BLINKY_KEY_FUNCTION_EVENT_H_ */
diff --git a/inc/keyboard_core.h b/inc/keyboard_core.h
index 8dfda05..571932f 100644
--- a/inc/keyboard_core.h
+++ b/inc/keyboard_core.h
@@ -8,6 +8,8 @@ extern "C" {
 #endif
 
 #define KEYBOARD_BOOT_REPORT_SIZE 8U
+#define KEYBOARD_PROTOCOL_USAGE_MAX 0xE7U
+#define KEYBOARD_PROTOCOL_BITMAP_BYTES ((KEYBOARD_PROTOCOL_USAGE_MAX + 8U) / 8U)
 #define KEYBOARD_NKRO_USAGE_MAX 0xDFU
 #define KEYBOARD_NKRO_BITMAP_BYTES ((KEYBOARD_NKRO_USAGE_MAX + 8U) / 8U)
 #define KEYBOARD_NKRO_REPORT_SIZE (1U + KEYBOARD_NKRO_BITMAP_BYTES)
diff --git a/inc/protocol_module.h b/inc/protocol_module.h
index e04ab93..64283f7 100644
--- a/inc/protocol_module.h
+++ b/inc/protocol_module.h
@@ -10,6 +10,10 @@ extern "C" {
 
 #define CDC_PROTO_TYPE_HELLO_REQ 0x01U
 #define CDC_PROTO_TYPE_HELLO_RSP 0x02U
+#define CDC_PROTO_TYPE_BITMAP 0x10U
+#define CDC_PROTO_TYPE_FUNCTION_KEY_EVENT 0x20U
+#define CDC_PROTO_TYPE_ACK 0x7EU
+#define CDC_PROTO_TYPE_ERROR 0x7FU
 
 int protocol_module_process_cdc_packet(uint8_t req_type,
 				       const uint8_t *req_payload,
diff --git a/proto/device_comm.options b/proto/device_comm.options
new file mode 100644
index 0000000..82623b7
--- /dev/null
+++ b/proto/device_comm.options
@@ -0,0 +1 @@
+Bitmap.usage_bitmap max_size:29
diff --git a/proto/device_comm.proto b/proto/device_comm.proto
index 63ad07d..7463555 100644
--- a/proto/device_comm.proto
+++ b/proto/device_comm.proto
@@ -13,9 +13,44 @@ message HelloRsp {
   uint32 capability_flags = 6;
 }
 
+message Bitmap {
+  bytes usage_bitmap = 1;
+}
+
+enum KeyAction {
+  KEY_ACTION_RELEASE = 0;
+  KEY_ACTION_PRESS = 1;
+}
+
+message FunctionKeyEvent {
+  uint32 usage = 1;
+  KeyAction action = 2;
+}
+
+message Ack {
+  uint32 acked_type = 1;
+}
+
+enum ErrorCode {
+  ERROR_CODE_NONE = 0;
+  ERROR_CODE_UNKNOWN_TYPE = 1;
+  ERROR_CODE_INVALID_LENGTH = 2;
+  ERROR_CODE_INVALID_PARAM = 3;
+  ERROR_CODE_NOT_READY = 4;
+}
+
+message Error {
+  uint32 error_type = 1;
+  ErrorCode error_code = 2;
+}
+
 message CdcPacketBody {
   oneof body {
     HelloReq hello_req = 1;
     HelloRsp hello_rsp = 2;
+    Bitmap bitmap = 3;
+    FunctionKeyEvent function_key_event = 4;
+    Ack ack = 5;
+    Error error = 6;
   }
 }
diff --git a/src/cdc_wrapper_module.c b/src/cdc_wrapper_module.c
index af110c1..10f41f0 100644
--- a/src/cdc_wrapper_module.c
+++ b/src/cdc_wrapper_module.c
@@ -12,6 +12,7 @@
 
 #include <zephyr/logging/log.h>
 
+#include "cdc_proto_tx_event.h"
 #include "protocol_module.h"
 #include "usb_cdc_rx_event.h"
 #include "usb_cdc_tx_event.h"
@@ -106,7 +107,8 @@ static void process_complete_frame(void)
 		return;
 	}
 
-	LOG_INF("CDC HelloRsp encoded len:%u", (uint32_t)rsp_payload_len);
+	LOG_INF("CDC response type:0x%02x len:%u",
+		rsp_type, (uint32_t)rsp_payload_len);
 	submit_tx_frame(rsp_type, rsp_payload, rsp_payload_len);
 }
 
@@ -183,6 +185,23 @@ static bool handle_usb_cdc_rx_event(const struct usb_cdc_rx_event *event)
 	return false;
 }
 
+static bool handle_cdc_proto_tx_event(const struct cdc_proto_tx_event *event)
+{
+	if (!running) {
+		return false;
+	}
+
+	if (event->dyndata.size > CDC_WRAPPER_MAX_PAYLOAD_LEN) {
+		LOG_WRN("Drop CDC proto TX len:%u max:%u",
+			(uint32_t)event->dyndata.size,
+			(uint32_t)CDC_WRAPPER_MAX_PAYLOAD_LEN);
+		return false;
+	}
+
+	submit_tx_frame(event->type, event->dyndata.data, event->dyndata.size);
+	return false;
+}
+
 static int module_init(void)
 {
 	parser_reset();
@@ -215,6 +234,10 @@ static bool app_event_handler(const struct app_event_header *aeh)
 		return handle_usb_cdc_rx_event(cast_usb_cdc_rx_event(aeh));
 	}
 
+	if (is_cdc_proto_tx_event(aeh)) {
+		return handle_cdc_proto_tx_event(cast_cdc_proto_tx_event(aeh));
+	}
+
 	if (is_module_state_event(aeh)) {
 		const struct module_state_event *event = cast_module_state_event(aeh);
 
@@ -269,6 +292,7 @@ static bool app_event_handler(const struct app_event_header *aeh)
 }
 
 APP_EVENT_LISTENER(MODULE, app_event_handler);
+APP_EVENT_SUBSCRIBE(MODULE, cdc_proto_tx_event);
 APP_EVENT_SUBSCRIBE(MODULE, module_state_event);
 APP_EVENT_SUBSCRIBE(MODULE, usb_cdc_rx_event);
 APP_EVENT_SUBSCRIBE_EARLY(MODULE, power_down_event);
diff --git a/src/events/cdc_proto_tx_event.c b/src/events/cdc_proto_tx_event.c
new file mode 100644
index 0000000..e1dcffe
--- /dev/null
+++ b/src/events/cdc_proto_tx_event.c
@@ -0,0 +1,29 @@
+#include "cdc_proto_tx_event.h"
+
+static void log_cdc_proto_tx_event(const struct app_event_header *aeh)
+{
+	const struct cdc_proto_tx_event *event = cast_cdc_proto_tx_event(aeh);
+
+	APP_EVENT_MANAGER_LOG(aeh, "type:0x%02x len:%zu",
+			      event->type, event->dyndata.size);
+}
+
+static void profile_cdc_proto_tx_event(struct log_event_buf *buf,
+				       const struct app_event_header *aeh)
+{
+	const struct cdc_proto_tx_event *event = cast_cdc_proto_tx_event(aeh);
+
+	nrf_profiler_log_encode_uint8(buf, event->type);
+	nrf_profiler_log_encode_uint8(buf, (uint8_t)event->dyndata.size);
+}
+
+APP_EVENT_INFO_DEFINE(cdc_proto_tx_event,
+		      ENCODE(NRF_PROFILER_ARG_U8, NRF_PROFILER_ARG_U8),
+		      ENCODE("type", "len"),
+		      profile_cdc_proto_tx_event);
+
+APP_EVENT_TYPE_DEFINE(cdc_proto_tx_event,
+		      log_cdc_proto_tx_event,
+		      &cdc_proto_tx_event_info,
+		      APP_EVENT_FLAGS_CREATE(
+			      APP_EVENT_TYPE_FLAGS_INIT_LOG_ENABLE));
diff --git a/src/events/function_bitmap_update_event.c b/src/events/function_bitmap_update_event.c
new file mode 100644
index 0000000..22c733e
--- /dev/null
+++ b/src/events/function_bitmap_update_event.c
@@ -0,0 +1,24 @@
+#include "function_bitmap_update_event.h"
+
+static void log_function_bitmap_update_event(const struct app_event_header *aeh)
+{
+	APP_EVENT_MANAGER_LOG(aeh, "bitmap updated");
+}
+
+static void profile_function_bitmap_update_event(struct log_event_buf *buf,
+						 const struct app_event_header *aeh)
+{
+	ARG_UNUSED(buf);
+	ARG_UNUSED(aeh);
+}
+
+APP_EVENT_INFO_DEFINE(function_bitmap_update_event,
+		      ENCODE(),
+		      ENCODE(),
+		      profile_function_bitmap_update_event);
+
+APP_EVENT_TYPE_DEFINE(function_bitmap_update_event,
+		      log_function_bitmap_update_event,
+		      &function_bitmap_update_event_info,
+		      APP_EVENT_FLAGS_CREATE(
+			      APP_EVENT_TYPE_FLAGS_INIT_LOG_ENABLE));
diff --git a/src/events/key_function_event.c b/src/events/key_function_event.c
new file mode 100644
index 0000000..9efb9c5
--- /dev/null
+++ b/src/events/key_function_event.c
@@ -0,0 +1,43 @@
+#include "key_function_event.h"
+
+static const char *action_name(uint8_t action)
+{
+	switch (action) {
+	case KEY_FUNCTION_ACTION_RELEASE:
+		return "release";
+
+	case KEY_FUNCTION_ACTION_PRESS:
+		return "press";
+
+	default:
+		return "unknown";
+	}
+}
+
+static void log_key_function_event(const struct app_event_header *aeh)
+{
+	const struct key_function_event *event = cast_key_function_event(aeh);
+
+	APP_EVENT_MANAGER_LOG(aeh, "usage:0x%04x action:%s",
+			      event->usage, action_name(event->action));
+}
+
+static void profile_key_function_event(struct log_event_buf *buf,
+				       const struct app_event_header *aeh)
+{
+	const struct key_function_event *event = cast_key_function_event(aeh);
+
+	nrf_profiler_log_encode_uint16(buf, event->usage);
+	nrf_profiler_log_encode_uint8(buf, event->action);
+}
+
+APP_EVENT_INFO_DEFINE(key_function_event,
+		      ENCODE(NRF_PROFILER_ARG_U16, NRF_PROFILER_ARG_U8),
+		      ENCODE("usage", "action"),
+		      profile_key_function_event);
+
+APP_EVENT_TYPE_DEFINE(key_function_event,
+		      log_key_function_event,
+		      &key_function_event_info,
+		      APP_EVENT_FLAGS_CREATE(
+			      APP_EVENT_TYPE_FLAGS_INIT_LOG_ENABLE));
diff --git a/src/keyboard_core_module.c b/src/keyboard_core_module.c
index 1c82589..e6c7abe 100644
--- a/src/keyboard_core_module.c
+++ b/src/keyboard_core_module.c
@@ -15,8 +15,10 @@
 #include <zephyr/sys/util.h>
 
 #include "encoder_event.h"
+#include "function_bitmap_update_event.h"
 #include "keyboard_core.h"
 #include "keyboard_hid_report_event.h"
+#include "key_function_event.h"
 #include "mode_switch_event.h"
 #include "set_protocol_event.h"
 
@@ -39,8 +41,8 @@ struct keymap_entry {
 };
 
 struct keyboard_state {
-	uint8_t modifiers;
-	uint8_t keys_bitmap[KEYBOARD_NKRO_BITMAP_BYTES];
+	uint8_t pressed_usage_bitmap[KEYBOARD_PROTOCOL_BITMAP_BYTES];
+	uint8_t function_pressed_bitmap[KEYBOARD_PROTOCOL_BITMAP_BYTES];
 	uint32_t consumer_bits;
 };
 
@@ -85,6 +87,7 @@ static const uint16_t consumer_usage_map[KEYBOARD_CONSUMER_CTRL_COUNT] = {
 
 static struct keyboard_state keyboard_state;
 static struct keyboard_reports_cache reports_cache;
+static uint8_t function_usage_mask[KEYBOARD_PROTOCOL_BITMAP_BYTES];
 static enum keyboard_protocol_mode transport_protocol_modes[HID_TRANSPORT_COUNT] = {
 	[HID_TRANSPORT_USB] = KEYBOARD_PROTOCOL_MODE_REPORT,
 	[HID_TRANSPORT_BLE] = KEYBOARD_PROTOCOL_MODE_REPORT,
@@ -143,40 +146,35 @@ static const struct keymap_entry *keymap_get(uint16_t key_id)
 	return NULL;
 }
 
-static bool usage_is_modifier(uint16_t usage_id)
+static bool usage_bitmap_test(const uint8_t *bitmap, uint16_t usage_id)
 {
-	return IN_RANGE(usage_id, KEYBOARD_USAGE_FIRST_MODIFIER,
-			KEYBOARD_USAGE_LAST_MODIFIER);
-}
-
-static bool keyboard_key_update(uint16_t usage_id, bool pressed)
-{
-	if (usage_is_modifier(usage_id)) {
-		uint8_t new_modifiers = keyboard_state.modifiers;
-
-		WRITE_BIT(new_modifiers, usage_id - KEYBOARD_USAGE_FIRST_MODIFIER, pressed);
-		if (new_modifiers == keyboard_state.modifiers) {
-			return false;
-		}
-
-		keyboard_state.modifiers = new_modifiers;
-		return true;
+	if ((bitmap == NULL) || (usage_id > KEYBOARD_PROTOCOL_USAGE_MAX)) {
+		return false;
 	}
 
-	if (usage_id > KEYBOARD_NKRO_USAGE_MAX) {
+	return (bitmap[usage_id / 8U] & BIT(usage_id % 8U)) != 0U;
+}
+
+static bool usage_bitmap_write(uint8_t *bitmap, uint16_t usage_id, bool pressed)
+{
+	uint8_t byte_idx;
+	uint8_t bit_idx;
+	bool was_pressed;
+
+	if ((bitmap == NULL) || (usage_id > KEYBOARD_PROTOCOL_USAGE_MAX)) {
 		LOG_WRN("Unsupported keyboard usage 0x%04x", usage_id);
 		return false;
 	}
 
-	uint8_t byte_idx = usage_id / 8U;
-	uint8_t bit_idx = usage_id % 8U;
-	bool was_pressed = (keyboard_state.keys_bitmap[byte_idx] & BIT(bit_idx)) != 0U;
+	byte_idx = usage_id / 8U;
+	bit_idx = usage_id % 8U;
+	was_pressed = (bitmap[byte_idx] & BIT(bit_idx)) != 0U;
 
 	if (was_pressed == pressed) {
 		return false;
 	}
 
-	WRITE_BIT(keyboard_state.keys_bitmap[byte_idx], bit_idx, pressed);
+	WRITE_BIT(bitmap[byte_idx], bit_idx, pressed);
 	return true;
 }
 
@@ -202,6 +200,11 @@ static void keyboard_state_clear(void)
 	memset(&keyboard_state, 0, sizeof(keyboard_state));
 }
 
+static void function_usage_mask_clear(void)
+{
+	memset(function_usage_mask, 0, sizeof(function_usage_mask));
+}
+
 static void reports_cache_invalidate(void)
 {
 	reports_cache.boot_valid = false;
@@ -209,19 +212,29 @@ static void reports_cache_invalidate(void)
 	reports_cache.consumer_valid = false;
 }
 
+static void build_effective_hid_bitmap(uint8_t bitmap[KEYBOARD_PROTOCOL_BITMAP_BYTES])
+{
+	for (size_t i = 0; i < KEYBOARD_PROTOCOL_BITMAP_BYTES; i++) {
+		bitmap[i] = keyboard_state.pressed_usage_bitmap[i] &
+			    (uint8_t)~keyboard_state.function_pressed_bitmap[i];
+	}
+}
+
 static void build_boot_report(uint8_t report[KEYBOARD_BOOT_REPORT_SIZE])
 {
+	uint8_t effective_hid_bitmap[KEYBOARD_PROTOCOL_BITMAP_BYTES];
 	size_t key_count = 0;
 
+	build_effective_hid_bitmap(effective_hid_bitmap);
 	memset(report, 0, KEYBOARD_BOOT_REPORT_SIZE);
-	report[0] = keyboard_state.modifiers;
+	report[0] = effective_hid_bitmap[KEYBOARD_PROTOCOL_BITMAP_BYTES - 1U];
 	report[1] = KEYBOARD_BOOT_RESERVED_BYTE;
 
 	for (uint16_t usage_id = 0; usage_id <= KEYBOARD_NKRO_USAGE_MAX; usage_id++) {
 		uint8_t byte_idx = usage_id / 8U;
 		uint8_t bit_idx = usage_id % 8U;
 
-		if ((keyboard_state.keys_bitmap[byte_idx] & BIT(bit_idx)) == 0U) {
+		if ((effective_hid_bitmap[byte_idx] & BIT(bit_idx)) == 0U) {
 			continue;
 		}
 
@@ -238,8 +251,11 @@ static void build_boot_report(uint8_t report[KEYBOARD_BOOT_REPORT_SIZE])
 
 static void build_nkro_report(uint8_t report[KEYBOARD_NKRO_REPORT_SIZE])
 {
-	report[0] = keyboard_state.modifiers;
-	memcpy(&report[1], keyboard_state.keys_bitmap, KEYBOARD_NKRO_BITMAP_BYTES);
+	uint8_t effective_hid_bitmap[KEYBOARD_PROTOCOL_BITMAP_BYTES];
+
+	build_effective_hid_bitmap(effective_hid_bitmap);
+	report[0] = effective_hid_bitmap[KEYBOARD_PROTOCOL_BITMAP_BYTES - 1U];
+	memcpy(&report[1], effective_hid_bitmap, KEYBOARD_NKRO_BITMAP_BYTES);
 }
 
 static uint16_t active_consumer_usage_get(void)
@@ -275,6 +291,15 @@ static void submit_keyboard_report_event(enum keyboard_report_type report_type,
 	APP_EVENT_SUBMIT(event);
 }
 
+static void submit_key_function_event(uint16_t usage_id, uint8_t action)
+{
+	struct key_function_event *event = new_key_function_event();
+
+	event->usage = usage_id;
+	event->action = action;
+	APP_EVENT_SUBMIT(event);
+}
+
 static void submit_consumer_fifo_frame(uint16_t usage_id)
 {
 	uint8_t report_buf[KEYBOARD_CONSUMER_REPORT_SIZE];
@@ -389,6 +414,17 @@ static void emit_all_reports(bool force)
 	}
 }
 
+static void emit_function_release_events(void)
+{
+	for (uint16_t usage_id = 0; usage_id <= KEYBOARD_PROTOCOL_USAGE_MAX; usage_id++) {
+		if (!usage_bitmap_test(keyboard_state.function_pressed_bitmap, usage_id)) {
+			continue;
+		}
+
+		submit_key_function_event(usage_id, KEY_FUNCTION_ACTION_RELEASE);
+	}
+}
+
 static void emit_release_reports(enum mode_switch_mode mode)
 {
 	struct keyboard_hid_report_event *event;
@@ -421,6 +457,7 @@ static int module_init(void)
 {
 	keyboard_state_clear();
 	reports_cache_invalidate();
+	function_usage_mask_clear();
 	mode_valid = false;
 	transport_protocol_modes[HID_TRANSPORT_USB] =
 		KEYBOARD_PROTOCOL_MODE_REPORT;
@@ -449,6 +486,7 @@ static void module_pause(void)
 	if (mode_valid) {
 		emit_release_reports(current_mode);
 	}
+	emit_function_release_events();
 
 	keyboard_state_clear();
 	reports_cache_invalidate();
@@ -472,8 +510,33 @@ static bool handle_button_event(const struct button_event *event)
 	}
 
 	if (entry->usage_type == KEY_USAGE_TYPE_KEYBOARD) {
-		changed = keyboard_key_update(entry->usage_id, event->pressed);
-		if (changed) {
+		bool routed_to_function;
+
+		changed = usage_bitmap_write(keyboard_state.pressed_usage_bitmap,
+						entry->usage_id, event->pressed);
+		if (!changed) {
+			return false;
+		}
+
+		if (event->pressed) {
+			routed_to_function =
+				usage_bitmap_test(function_usage_mask, entry->usage_id);
+			(void)usage_bitmap_write(keyboard_state.function_pressed_bitmap,
+						 entry->usage_id, routed_to_function);
+		} else {
+			routed_to_function =
+				usage_bitmap_test(keyboard_state.function_pressed_bitmap,
+						  entry->usage_id);
+			(void)usage_bitmap_write(keyboard_state.function_pressed_bitmap,
+						 entry->usage_id, false);
+		}
+
+		if (routed_to_function) {
+			submit_key_function_event(entry->usage_id,
+						  event->pressed ?
+							  KEY_FUNCTION_ACTION_PRESS :
+							  KEY_FUNCTION_ACTION_RELEASE);
+		} else {
 			emit_keys_report(false);
 		}
 	} else {
@@ -498,6 +561,7 @@ static bool handle_mode_switch_event(const struct mode_switch_event *event)
 	mode_changed = mode_valid && (current_mode != event->mode);
 	if (mode_changed) {
 		emit_release_reports(current_mode);
+		emit_function_release_events();
 		keyboard_state_clear();
 		reports_cache_invalidate();
 	}
@@ -526,6 +590,13 @@ static bool handle_encoder_event(const struct encoder_event *event)
 	return false;
 }
 
+static bool handle_function_bitmap_update_event(
+	const struct function_bitmap_update_event *event)
+{
+	memcpy(function_usage_mask, event->bitmap, sizeof(function_usage_mask));
+	return false;
+}
+
 static bool app_event_handler(const struct app_event_header *aeh)
 {
 	if (is_button_event(aeh)) {
@@ -536,6 +607,11 @@ static bool app_event_handler(const struct app_event_header *aeh)
 		return handle_encoder_event(cast_encoder_event(aeh));
 	}
 
+	if (is_function_bitmap_update_event(aeh)) {
+		return handle_function_bitmap_update_event(
+			cast_function_bitmap_update_event(aeh));
+	}
+
 	if (is_set_protocol_event(aeh)) {
 		const struct set_protocol_event *event = cast_set_protocol_event(aeh);
 		enum hid_transport active_transport;
@@ -623,6 +699,7 @@ static bool app_event_handler(const struct app_event_header *aeh)
 APP_EVENT_LISTENER(MODULE, app_event_handler);
 APP_EVENT_SUBSCRIBE(MODULE, button_event);
 APP_EVENT_SUBSCRIBE(MODULE, encoder_event);
+APP_EVENT_SUBSCRIBE(MODULE, function_bitmap_update_event);
 APP_EVENT_SUBSCRIBE(MODULE, set_protocol_event);
 APP_EVENT_SUBSCRIBE(MODULE, mode_switch_event);
 APP_EVENT_SUBSCRIBE(MODULE, module_state_event);
diff --git a/src/protocol_module.c b/src/protocol_module.c
index 6cd1d2c..29823c8 100644
--- a/src/protocol_module.c
+++ b/src/protocol_module.c
@@ -2,24 +2,42 @@
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
+#include <string.h>
+
+#include <app_event_manager.h>
+
+#define MODULE protocol_module
+#include <caf/events/module_state_event.h>
+#include <caf/events/power_event.h>
 
 #include <zephyr/logging/log.h>
+#include <zephyr/sys/util.h>
 
 #include <pb_decode.h>
 #include <pb_encode.h>
 
 #include <proto/device_comm.pb.h>
 
+#include "cdc_proto_tx_event.h"
+#include "function_bitmap_update_event.h"
+#include "key_function_event.h"
 #include "protocol_module.h"
+#include "usb_device_state_event.h"
 
-LOG_MODULE_REGISTER(protocol_module, LOG_LEVEL_INF);
+LOG_MODULE_REGISTER(MODULE, LOG_LEVEL_INF);
 
 #define PROTOCOL_VERSION 1U
 #define PROTOCOL_VENDOR_ID 0x1915U
 #define PROTOCOL_PRODUCT_ID 0x52F0U
 #define PROTOCOL_FIRMWARE_MAJOR 0U
 #define PROTOCOL_FIRMWARE_MINOR 0U
-#define PROTOCOL_CAPABILITY_FLAGS 0U
+#define PROTOCOL_CAPABILITY_FLAGS BIT(0)
+
+static bool initialized;
+static bool running;
+static bool keyboard_core_ready;
+static bool usb_active;
+static bool hello_done;
 
 static bool type_matches_body(uint8_t type, const CdcPacketBody *body)
 {
@@ -28,6 +46,14 @@ static bool type_matches_body(uint8_t type, const CdcPacketBody *body)
 		return body->which_body == CdcPacketBody_hello_req_tag;
 	case CDC_PROTO_TYPE_HELLO_RSP:
 		return body->which_body == CdcPacketBody_hello_rsp_tag;
+	case CDC_PROTO_TYPE_BITMAP:
+		return body->which_body == CdcPacketBody_bitmap_tag;
+	case CDC_PROTO_TYPE_FUNCTION_KEY_EVENT:
+		return body->which_body == CdcPacketBody_function_key_event_tag;
+	case CDC_PROTO_TYPE_ACK:
+		return body->which_body == CdcPacketBody_ack_tag;
+	case CDC_PROTO_TYPE_ERROR:
+		return body->which_body == CdcPacketBody_error_tag;
 	default:
 		return false;
 	}
@@ -53,15 +79,29 @@ static int decode_body(const uint8_t *payload, size_t payload_len,
 	return 0;
 }
 
+static int encode_body(const CdcPacketBody *body, uint8_t *payload,
+		       size_t payload_buf_size, size_t *payload_len)
+{
+	pb_ostream_t stream;
+
+	if ((body == NULL) || (payload == NULL) || (payload_len == NULL)) {
+		return -EINVAL;
+	}
+
+	stream = pb_ostream_from_buffer(payload, payload_buf_size);
+	if (!pb_encode(&stream, CdcPacketBody_fields, body)) {
+		LOG_WRN("pb_encode failed: %s", PB_GET_ERROR(&stream));
+		return -EIO;
+	}
+
+	*payload_len = stream.bytes_written;
+	return 0;
+}
+
 static int encode_hello_rsp(uint8_t *rsp_payload, size_t rsp_payload_buf_size,
 			    size_t *rsp_payload_len)
 {
 	CdcPacketBody body = CdcPacketBody_init_zero;
-	pb_ostream_t stream;
-
-	if ((rsp_payload == NULL) || (rsp_payload_len == NULL)) {
-		return -EINVAL;
-	}
 
 	body.which_body = CdcPacketBody_hello_rsp_tag;
 	body.body.hello_rsp.protocol_version = PROTOCOL_VERSION;
@@ -71,17 +111,145 @@ static int encode_hello_rsp(uint8_t *rsp_payload, size_t rsp_payload_buf_size,
 	body.body.hello_rsp.firmware_minor = PROTOCOL_FIRMWARE_MINOR;
 	body.body.hello_rsp.capability_flags = PROTOCOL_CAPABILITY_FLAGS;
 
-	stream = pb_ostream_from_buffer(rsp_payload, rsp_payload_buf_size);
+	return encode_body(&body, rsp_payload, rsp_payload_buf_size, rsp_payload_len);
+}
 
-	if (!pb_encode(&stream, CdcPacketBody_fields, &body)) {
-		LOG_WRN("pb_encode failed: %s", PB_GET_ERROR(&stream));
-		return -EIO;
+static int encode_ack(uint8_t acked_type, uint8_t *rsp_payload,
+		      size_t rsp_payload_buf_size, size_t *rsp_payload_len)
+{
+	CdcPacketBody body = CdcPacketBody_init_zero;
+
+	body.which_body = CdcPacketBody_ack_tag;
+	body.body.ack.acked_type = acked_type;
+
+	return encode_body(&body, rsp_payload, rsp_payload_buf_size, rsp_payload_len);
+}
+
+static int encode_error(uint8_t error_type, ErrorCode error_code,
+			uint8_t *rsp_payload, size_t rsp_payload_buf_size,
+			size_t *rsp_payload_len)
+{
+	CdcPacketBody body = CdcPacketBody_init_zero;
+
+	body.which_body = CdcPacketBody_error_tag;
+	body.body.error.error_type = error_type;
+	body.body.error.error_code = error_code;
+
+	return encode_body(&body, rsp_payload, rsp_payload_buf_size, rsp_payload_len);
+}
+
+static int encode_function_key_event(uint16_t usage, uint8_t action,
+				     uint8_t *payload,
+				     size_t payload_buf_size,
+				     size_t *payload_len)
+{
+	CdcPacketBody body = CdcPacketBody_init_zero;
+
+	body.which_body = CdcPacketBody_function_key_event_tag;
+	body.body.function_key_event.usage = usage;
+	body.body.function_key_event.action = (KeyAction)action;
+
+	return encode_body(&body, payload, payload_buf_size, payload_len);
+}
+
+static int submit_cdc_proto_tx_event(uint8_t type, const uint8_t *payload,
+				     size_t payload_len)
+{
+	struct cdc_proto_tx_event *event;
+
+	if ((payload == NULL) && (payload_len > 0U)) {
+		return -EINVAL;
 	}
 
-	*rsp_payload_len = stream.bytes_written;
+	event = new_cdc_proto_tx_event(payload_len);
+	event->type = type;
+	if (payload_len > 0U) {
+		memcpy(event->dyndata.data, payload, payload_len);
+	}
+
+	APP_EVENT_SUBMIT(event);
 	return 0;
 }
 
+static int submit_function_bitmap_update_event(const Bitmap *bitmap)
+{
+	struct function_bitmap_update_event *event;
+
+	if ((bitmap == NULL) ||
+	    (bitmap->usage_bitmap.size != KEYBOARD_PROTOCOL_BITMAP_BYTES)) {
+		return -EINVAL;
+	}
+
+	event = new_function_bitmap_update_event();
+	memcpy(event->bitmap, bitmap->usage_bitmap.bytes,
+	       KEYBOARD_PROTOCOL_BITMAP_BYTES);
+	APP_EVENT_SUBMIT(event);
+
+	return 0;
+}
+
+static int encode_error_response(uint8_t req_type, ErrorCode error_code,
+				 uint8_t *rsp_type, uint8_t *rsp_payload,
+				 size_t rsp_payload_buf_size,
+				 size_t *rsp_payload_len)
+{
+	int err;
+
+	err = encode_error(req_type, error_code, rsp_payload,
+			   rsp_payload_buf_size, rsp_payload_len);
+	if (err) {
+		return err;
+	}
+
+	*rsp_type = CDC_PROTO_TYPE_ERROR;
+	return 0;
+}
+
+static int encode_ack_response(uint8_t acked_type, uint8_t *rsp_type,
+			       uint8_t *rsp_payload,
+			       size_t rsp_payload_buf_size,
+			       size_t *rsp_payload_len)
+{
+	int err;
+
+	err = encode_ack(acked_type, rsp_payload, rsp_payload_buf_size,
+			 rsp_payload_len);
+	if (err) {
+		return err;
+	}
+
+	*rsp_type = CDC_PROTO_TYPE_ACK;
+	return 0;
+}
+
+static int module_init(void)
+{
+	keyboard_core_ready = false;
+	usb_active = false;
+	hello_done = false;
+	return 0;
+}
+
+static int module_start(void)
+{
+	if (running) {
+		return 0;
+	}
+
+	running = true;
+	return 0;
+}
+
+static void module_pause(void)
+{
+	if (!running) {
+		return;
+	}
+
+	hello_done = false;
+	running = false;
+}
+
 int protocol_module_process_cdc_packet(uint8_t req_type,
 				       const uint8_t *req_payload,
 				       size_t req_payload_len,
@@ -97,15 +265,23 @@ int protocol_module_process_cdc_packet(uint8_t req_type,
 		return -EINVAL;
 	}
 
+	if (!running) {
+		return -EAGAIN;
+	}
+
 	err = decode_body(req_payload, req_payload_len, &body);
 	if (err) {
-		return err;
+		return encode_error_response(req_type, ErrorCode_ERROR_CODE_INVALID_LENGTH,
+					     rsp_type, rsp_payload,
+					     rsp_payload_buf_size, rsp_payload_len);
 	}
 
 	if (!type_matches_body(req_type, &body)) {
 		LOG_WRN("CDC type/body mismatch type:0x%02x body_case:%d",
 			req_type, body.which_body);
-		return -EBADMSG;
+		return encode_error_response(req_type, ErrorCode_ERROR_CODE_INVALID_PARAM,
+					     rsp_type, rsp_payload,
+					     rsp_payload_buf_size, rsp_payload_len);
 	}
 
 	switch (req_type) {
@@ -118,6 +294,7 @@ int protocol_module_process_cdc_packet(uint8_t req_type,
 				body.body.hello_req.protocol_version);
 		}
 
+		hello_done = true;
 		err = encode_hello_rsp(rsp_payload, rsp_payload_buf_size, rsp_payload_len);
 		if (err) {
 			return err;
@@ -126,8 +303,158 @@ int protocol_module_process_cdc_packet(uint8_t req_type,
 		*rsp_type = CDC_PROTO_TYPE_HELLO_RSP;
 		return 0;
 
+	case CDC_PROTO_TYPE_BITMAP:
+		if (!hello_done) {
+			return encode_error_response(req_type, ErrorCode_ERROR_CODE_NOT_READY,
+						     rsp_type, rsp_payload,
+						     rsp_payload_buf_size,
+						     rsp_payload_len);
+		}
+
+		if (!keyboard_core_ready) {
+			return encode_error_response(req_type, ErrorCode_ERROR_CODE_NOT_READY,
+						     rsp_type, rsp_payload,
+						     rsp_payload_buf_size,
+						     rsp_payload_len);
+		}
+
+		if (body.body.bitmap.usage_bitmap.size != KEYBOARD_PROTOCOL_BITMAP_BYTES) {
+			LOG_WRN("Bitmap len:%u expected:%u",
+				(unsigned int)body.body.bitmap.usage_bitmap.size,
+				KEYBOARD_PROTOCOL_BITMAP_BYTES);
+			return encode_error_response(req_type, ErrorCode_ERROR_CODE_INVALID_LENGTH,
+						     rsp_type, rsp_payload,
+						     rsp_payload_buf_size,
+						     rsp_payload_len);
+		}
+
+		err = submit_function_bitmap_update_event(&body.body.bitmap);
+		if (err) {
+			return encode_error_response(req_type, ErrorCode_ERROR_CODE_INVALID_PARAM,
+						     rsp_type, rsp_payload,
+						     rsp_payload_buf_size,
+						     rsp_payload_len);
+		}
+
+		return encode_ack_response(req_type, rsp_type, rsp_payload,
+					   rsp_payload_buf_size, rsp_payload_len);
+
 	default:
 		LOG_WRN("Unsupported CDC protocol type:0x%02x", req_type);
-		return -ENOTSUP;
+		return encode_error_response(req_type, ErrorCode_ERROR_CODE_UNKNOWN_TYPE,
+					     rsp_type, rsp_payload,
+					     rsp_payload_buf_size, rsp_payload_len);
 	}
 }
+
+static bool handle_key_function_event(const struct key_function_event *event)
+{
+	uint8_t payload[64];
+	size_t payload_len;
+	int err;
+
+	if (!running || !usb_active || !hello_done) {
+		return false;
+	}
+
+	err = encode_function_key_event(event->usage, event->action, payload,
+					sizeof(payload), &payload_len);
+	if (err) {
+		LOG_WRN("FunctionKeyEvent encode failed (%d)", err);
+		return false;
+	}
+
+	err = submit_cdc_proto_tx_event(CDC_PROTO_TYPE_FUNCTION_KEY_EVENT,
+					payload, payload_len);
+	if (err) {
+		LOG_WRN("FunctionKeyEvent submit failed (%d)", err);
+	}
+
+	return false;
+}
+
+static bool handle_usb_device_state_event(const struct usb_device_state_event *event)
+{
+	usb_active = (event->state == USB_DEVICE_STATE_ACTIVE);
+	if (!usb_active) {
+		hello_done = false;
+	}
+
+	return false;
+}
+
+static bool app_event_handler(const struct app_event_header *aeh)
+{
+	if (is_key_function_event(aeh)) {
+		return handle_key_function_event(cast_key_function_event(aeh));
+	}
+
+	if (is_usb_device_state_event(aeh)) {
+		return handle_usb_device_state_event(cast_usb_device_state_event(aeh));
+	}
+
+	if (is_module_state_event(aeh)) {
+		const struct module_state_event *event = cast_module_state_event(aeh);
+		int err;
+
+		if (check_state(event, MODULE_ID(main), MODULE_STATE_READY)) {
+			if (!initialized) {
+				err = module_init();
+				if (err) {
+					module_set_state(MODULE_STATE_ERROR);
+					return false;
+				}
+
+				initialized = true;
+			}
+
+			err = module_start();
+			if (err) {
+				module_set_state(MODULE_STATE_ERROR);
+			} else {
+				module_set_state(MODULE_STATE_READY);
+			}
+
+			return false;
+		}
+
+		if (check_state(event, MODULE_ID(keyboard_core_module), MODULE_STATE_READY)) {
+			keyboard_core_ready = true;
+			return false;
+		}
+
+		return false;
+	}
+
+	if (is_power_down_event(aeh)) {
+		if (initialized) {
+			module_pause();
+			module_set_state(MODULE_STATE_STANDBY);
+		}
+
+		return false;
+	}
+
+	if (is_wake_up_event(aeh)) {
+		if (initialized) {
+			int err = module_start();
+
+			if (err) {
+				module_set_state(MODULE_STATE_ERROR);
+			} else {
+				module_set_state(MODULE_STATE_READY);
+			}
+		}
+
+		return false;
+	}
+
+	return false;
+}
+
+APP_EVENT_LISTENER(MODULE, app_event_handler);
+APP_EVENT_SUBSCRIBE(MODULE, key_function_event);
+APP_EVENT_SUBSCRIBE(MODULE, module_state_event);
+APP_EVENT_SUBSCRIBE(MODULE, usb_device_state_event);
+APP_EVENT_SUBSCRIBE_EARLY(MODULE, power_down_event);
+APP_EVENT_SUBSCRIBE(MODULE, wake_up_event);