diff --git a/docs/firmware_proto_transport.md b/docs/firmware_proto_transport.md
index 49e880b..8fd7b6f 100644
--- a/docs/firmware_proto_transport.md
+++ b/docs/firmware_proto_transport.md
@@ -36,3 +36,26 @@ Design notes:
 - CDC transport module
 - GATT transport module
 - nanopb integration and generated protocol code
+
+### Node 2: keyboard split point
+
+Files updated in this step:
+
+- `src/modules/keyboard_module.c`
+
+Design notes:
+
+- reuse the existing keymap and HID path
+- add one explicit split point before HID submission
+- keep normal keys on HID
+- send configured function keys to private transport only
+
+Implemented behavior:
+
+- store the 29-byte function bitmap
+- for keyboard usages marked as function keys:
+  - stop normal HID reporting
+  - emit `function_key_event`
+- for consumer usages marked as function keys:
+  - stop normal HID reporting
+  - emit `function_key_event`
diff --git a/src/modules/keyboard_module.c b/src/modules/keyboard_module.c
index 0fef737..35c3c4d 100644
--- a/src/modules/keyboard_module.c
+++ b/src/modules/keyboard_module.c
@@ -14,6 +14,8 @@
 #include "hid_protocol_event.h"
 #include "hid_report_event.h"
 #include "hid_vendor_mask_event.h"
+#include "function_bitmap_event.h"
+#include "function_key_event.h"
 #include "qdec_step_event.h"
 
 #include <zephyr/sys/util.h>
@@ -100,6 +102,7 @@ struct keyboard_state {
 	uint8_t physical_usage_bm[KEYBOARD_BITMAP_SIZE];
 	uint8_t mask_modifier_bm;
 	uint8_t mask_bm[KEYBOARD_BITMAP_SIZE];
+	uint8_t function_bm[KEYBOARD_BITMAP_SIZE];
 	enum hid_protocol_type current_protocol;
 	uint16_t consumer_usage;
 };
@@ -124,6 +127,16 @@ static void keyboard_mask_init(void)
 {
 	ks.mask_modifier_bm = 0xFF;
 	memset(ks.mask_bm, 0xFF, sizeof(ks.mask_bm));
+	memset(ks.function_bm, 0, sizeof(ks.function_bm));
+}
+
+static bool function_usage_active(uint16_t usage_id)
+{
+	if (usage_id > KEYBOARD_USAGE_MAX) {
+		return false;
+	}
+
+	return (ks.function_bm[usage_id / 8] & BIT(usage_id % 8)) != 0U;
 }
 
 /* 查询某 usage 位在当前键盘位图里是否处于按下状态。 */
@@ -298,6 +311,11 @@ static void submit_consumer_click_usage(uint16_t usage_id)
  */
 static bool handle_keyboard_usage_event(const struct hid_keymap *map, bool pressed)
 {
+	if (function_usage_active(map->usage_id)) {
+		function_key_event_submit(map->usage_id, pressed);
+		return false;
+	}
+
 	if (!keyboard_usage_update(map->usage_id, pressed))
 		return false;
 
@@ -313,6 +331,11 @@ static bool handle_keyboard_usage_event(const struct hid_keymap *map, bool press
  */
 static bool handle_consumer_usage_event(const struct hid_keymap *map, bool pressed)
 {
+	if (function_usage_active(map->usage_id)) {
+		function_key_event_submit(map->usage_id, pressed);
+		return false;
+	}
+
 	if (active_protocol_get() == HID_PROTO_BOOT)
 		return false;
 
@@ -381,6 +404,21 @@ static bool handle_hid_vendor_mask_event(const struct hid_vendor_mask_event *eve
 	return false;
 }
 
+static bool handle_function_bitmap_event(const struct function_bitmap_event *event)
+{
+	const uint8_t *data = function_bitmap_event_get_data(event);
+	size_t size = function_bitmap_event_get_size(event);
+
+	if (size != sizeof(ks.function_bm)) {
+		LOG_WRN("Ignore function bitmap len=%u expect=%u",
+			size, sizeof(ks.function_bm));
+		return false;
+	}
+
+	memcpy(ks.function_bm, data, sizeof(ks.function_bm));
+	return false;
+}
+
 static bool handle_qdec_step_event(const struct qdec_step_event *event)
 {
 	int8_t step = qdec_step_event_get_step(event);
@@ -415,6 +453,10 @@ static bool app_event_handler(const struct app_event_header *aeh)
 		return handle_hid_vendor_mask_event(cast_hid_vendor_mask_event(aeh));
 	}
 
+	if (is_function_bitmap_event(aeh)) {
+		return handle_function_bitmap_event(cast_function_bitmap_event(aeh));
+	}
+
 	if (is_module_state_event(aeh)) {
 		const struct module_state_event *event = cast_module_state_event(aeh);
 
@@ -436,5 +478,6 @@ APP_EVENT_LISTENER(MODULE, app_event_handler);
 APP_EVENT_SUBSCRIBE(MODULE, button_event);
 APP_EVENT_SUBSCRIBE(MODULE, hid_protocol_event);
 APP_EVENT_SUBSCRIBE(MODULE, hid_vendor_mask_event);
+APP_EVENT_SUBSCRIBE(MODULE, function_bitmap_event);
 APP_EVENT_SUBSCRIBE(MODULE, qdec_step_event);
 APP_EVENT_SUBSCRIBE(MODULE, module_state_event);