feat: add LED activity indication for data transmission

- Blue LED blinks when scanning for devices (not connected)
- Solid green LED when connected but idle
- Flickering green LED when connected and data is actively flowing
- Added data activity tracking to BLE HID notification handler
- 20ms LED toggle rate for responsive visual feedback
- 100ms activity window for immediate response to data flow changes

The LED now provides real-time visual feedback of the bridge connection
status and data transmission activity.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: RobertDaleSmith

app/src/ble_hid.c

@@ -154,6 +154,15 @@ static uint8_t hogp_notify_cb(struct bt_hogp *hogp,
 		} else {
 			k_sem_take(&ep_write_sem, K_FOREVER);
 			// printk("Report %u sent directly to USB", report_id);
+			
+			/* Trigger data activity callback for LED indication */
+			if (data_received_callback) {
+				data_received_callback(data, size);
+			}
+			
+			/* Also directly trigger transport layer data activity */
+			extern void ble_transport_mark_data_activity(void);
+			ble_transport_mark_data_activity();
 		}
 	}
 

app/src/ble_transport.c

@@ -33,6 +33,10 @@ static bool bridging_started = false;
 static bool hid_client_ready = false;
 static bool hid_discovery_complete = false;
 
+/* Data activity tracking for LED indication */
+static bool data_activity = false;
+static int64_t last_data_time = 0;
+
 /* HID Bridge callbacks */
 static ble_data_callback_t hid_data_callback = NULL;
 static ble_ready_callback_t hid_ready_callback = NULL;
@@ -154,6 +158,7 @@ int ble_transport_send_nus_data(const uint8_t *data, uint16_t len)
 		LOG_ERR("BLE Transport send failed: %d", err);
 	} else {
 		LOG_INF("BLE Transport send successful");
+		data_activity = true;  // Mark data activity for LED indication
 	}
 	return err;
 }
@@ -189,6 +194,7 @@ int ble_transport_send_hid_data(const uint8_t *data, uint16_t len)
 		LOG_ERR("BLE Transport HID send failed: %d", err);
 	} else {
 		LOG_INF("BLE Transport HID send successful");
+		data_activity = true;  // Mark data activity for LED indication
 	}
 	return err;
 }
@@ -232,6 +238,11 @@ static void ble_nus_data_received_cb(const uint8_t *data, uint16_t len)
 		LOG_INF("PACKET STRUCTURE: Type=0x%02x, Length=%d", data[0], len);
 	}
 
+	// Mark data activity for LED indication
+	data_activity = true;
+	last_data_time = k_uptime_get();
+	LOG_INF("=== DATA ACTIVITY MARKED ===");
+	
 	// Bridge NUS data directly to USB CDC
 	if (usb_cdc_send_callback) {
 		usb_cdc_send_callback(data, len);
@@ -289,6 +300,11 @@ static void ble_hid_data_received_cb(const uint8_t *data, uint16_t len)
 		LOG_INF("HID PACKET STRUCTURE: Type=0x%02x, Length=%d", data[0], len);
 	}
 
+	// Mark data activity for LED indication
+	data_activity = true;
+	last_data_time = k_uptime_get();
+	LOG_INF("=== DATA ACTIVITY MARKED ===");
+	
 	// Bridge HID data directly to USB HID
 	if (hid_data_callback) {
 		LOG_INF("Calling USB HID callback with %d bytes", len);
@@ -373,3 +389,32 @@ static void ble_central_disconnected_cb(struct bt_conn *conn, uint8_t reason)
 
 	LOG_INF("BLE Central disconnected - resetting both NUS and HID bridge states");
 }
+
+bool ble_transport_is_connected(void)
+{
+	return nus_client_ready || hid_client_ready;
+}
+
+bool ble_transport_has_data_activity(void)
+{
+	// Check if we've had data activity within the last 100ms
+	int64_t current_time = k_uptime_get();
+	if (data_activity && (current_time - last_data_time) < 100) {
+		LOG_DBG("BLE data activity detected (time diff: %lld ms)", current_time - last_data_time);
+		return true;
+	}
+	
+	// Reset if it's been too long
+	if ((current_time - last_data_time) >= 100) {
+		data_activity = false;
+	}
+	
+	return false;
+}
+
+void ble_transport_mark_data_activity(void)
+{
+	data_activity = true;
+	last_data_time = k_uptime_get();
+	LOG_INF("=== DATA ACTIVITY MARKED (DIRECT) ===");
+}

app/src/ble_transport.h

@@ -30,6 +30,10 @@ int ble_transport_register_usb_hid_callback(ble_data_callback_t cb);
 int ble_transport_send_nus_data(const uint8_t *data, uint16_t len);
 bool ble_transport_is_nus_ready(void);
 
+/* Connection status */
+bool ble_transport_is_connected(void);
+bool ble_transport_has_data_activity(void);
+
 /* Future HID Transport functions (for later integration) */
 int ble_transport_register_hid_data_callback(ble_data_callback_t cb);
 int ble_transport_register_hid_ready_callback(ble_ready_callback_t cb);

app/src/main.c

@@ -88,9 +88,22 @@ int main(void)
 
 	LOG_INF("Starting USB ↔ BLE bridge (NUS + HID)");
 
-	// LED for status indication
-	const struct gpio_dt_spec led0 = GPIO_DT_SPEC_GET(DT_ALIAS(led0), gpios);
+	// LED status indication system
+	const struct gpio_dt_spec led_blue = GPIO_DT_SPEC_GET(DT_ALIAS(led2), gpios);   // Blue LED
+	const struct gpio_dt_spec led_green = GPIO_DT_SPEC_GET(DT_ALIAS(led1), gpios);  // Green LED
 	static int led_counter = 0;
+	static bool data_activity = false;
+	
+	// Configure LEDs
+	if (!gpio_is_ready_dt(&led_blue) || !gpio_is_ready_dt(&led_green)) {
+		LOG_ERR("LED devices not ready");
+	} else {
+		gpio_pin_configure_dt(&led_blue, GPIO_OUTPUT);
+		gpio_pin_configure_dt(&led_green, GPIO_OUTPUT);
+		// Start with blue LED on (scanning state)
+		gpio_pin_set_dt(&led_blue, 1);
+		gpio_pin_set_dt(&led_green, 0);
+	}
 
 	for (;;) {
 		/* USB CDC ↔ BLE NUS Bridge */
@@ -105,6 +118,7 @@ int main(void)
 		if (bytes_read > 0) { // Data received from CDC
 			cdc_buffer[cdc_pos] = c;
 			cdc_pos++;
+			data_activity = true;  // Mark data activity
 
 			// Send complete command when we get newline
 			if (c == '\n' || c == '\r' || cdc_pos >= UART_BUF_SIZE) {
@@ -125,11 +139,43 @@ int main(void)
 			}
 		}
 
-		// Toggle LED every 1000 iterations (roughly every second)
+		// LED status system
 		led_counter++;
-		if (led_counter >= 1000) {
-			(void)gpio_pin_toggle(led0.port, led0.pin);
-			led_counter = 0;
+		
+		// Check BLE connection status and data activity
+		bool is_connected = ble_transport_is_connected();
+		bool ble_data_activity = ble_transport_has_data_activity();
+		
+		// Debug logging every second
+		if (led_counter % 1000 == 0) {
+			LOG_INF("LED: connected=%d, usb_data=%d, ble_data=%d", is_connected, data_activity, ble_data_activity);
+		}
+		
+		if (is_connected && (data_activity || ble_data_activity)) {
+			// Connected with data activity: Green flicker
+			if (led_counter % 20 == 0) {  // Very fast flicker every 20ms
+				gpio_pin_toggle_dt(&led_green);
+			}
+			// Turn off blue LED
+			gpio_pin_set_dt(&led_blue, 0);
+			
+		} else if (is_connected) {
+			// Connected but no data: Solid green
+			gpio_pin_set_dt(&led_green, 1);
+			gpio_pin_set_dt(&led_blue, 0);
+			
+		} else {
+			// Not connected: Blue blink (scanning)
+			gpio_pin_set_dt(&led_green, 0);
+			if (led_counter >= 500) {  // Slow blink every 500ms
+				gpio_pin_toggle_dt(&led_blue);
+				led_counter = 0;
+			}
+		}
+		
+		// Reset data activity flag periodically
+		if (led_counter % 100 == 0) {
+			data_activity = false;
 		}
 
 		// Small delay to prevent busy waiting

app/src/usb_hid.c

@@ -25,8 +25,8 @@ LOG_MODULE_REGISTER(usb_mouse, LOG_LEVEL_INF);
  * GLOBAL VARIABLES
  * ============================================================================ */
 
-/* LED for status indication */
-static const struct gpio_dt_spec led0 = GPIO_DT_SPEC_GET(DT_ALIAS(led0), gpios);
+/* LED for status indication (blue LED) */
+static const struct gpio_dt_spec led2 = GPIO_DT_SPEC_GET(DT_ALIAS(led2), gpios);
 
 /* USB HID device and semaphore - accessible to BLE module for direct sending */
 const struct device *hid_dev;
@@ -153,13 +153,13 @@ int usb_init(void)
 	/* Initialize USB endpoint semaphore */
 	k_sem_init(&ep_write_sem, 0, 1);
 
-	/* Configure status LED */
-	if (!gpio_is_ready_dt(&led0)) {
-		LOG_ERR("LED device %s is not ready", led0.port->name);
+	/* Configure status blue LED */
+	if (!gpio_is_ready_dt(&led2)) {
+		LOG_ERR("LED device %s is not ready", led2.port->name);
 		return -ENODEV;
 	}
 
-	ret = gpio_pin_configure_dt(&led0, GPIO_OUTPUT);
+	ret = gpio_pin_configure_dt(&led2, GPIO_OUTPUT);
 	if (ret < 0) {
 		LOG_ERR("Failed to configure the LED pin, error: %d", ret);
 		return ret;