BLE TX Power 동적 제어 (기본 4 dBm / Boost 8 dBm / 복귀 4 dBm)

- 광고, 연결 모두 기본 4 dBm 강제 (컨트롤러 기본이 +8이므로 명시적으로 낮춤)
- 연결 RSSI 추적 활성화(CONFIG_BT_CTLR_CONN_RSSI) + RSSI 모니터 재활성화

boards/nrf52840dk_nrf52840.conf

@@ -1,2 +1,3 @@
 CONFIG_BT_CTLR_TX_PWR_PLUS_8=y
 CONFIG_BT_CTLR_TX_PWR_DYNAMIC_CONTROL=y
+CONFIG_BT_CTLR_CONN_RSSI=y

src/ble/ble_service.c

@@ -50,6 +50,7 @@ static int64_t last_rx_conn_param_update_ms;
 #define BLE_TX_STUCK_MS              200
 #define BLE_TX_SLOW_COUNT              3
 #define BLE_TX_BUSY_STRESS_RETRY       4
+#define BLE_TX_RECOVER_HOLD_MS         10000   // 마지막 트리거 이후 이 시간 동안 트리거 없는 경우 TX power 복귀
 
 extern int bt_hci_get_conn_handle(const struct bt_conn *conn, uint16_t *conn_handle);
 
@@ -58,6 +59,7 @@ static bool current_conn_handle_valid;
 static int8_t current_tx_power_dbm = BLE_TX_POWER_NORMAL_DBM;
 static uint8_t low_rssi_count;
 static uint8_t slow_tx_count;
+static int64_t last_stress_ms;
 static struct k_work_delayable tx_power_monitor_work;
 
 #if IS_ENABLED(CONFIG_BT_SMP)
@@ -137,9 +139,64 @@ static int ble_set_conn_tx_power(int8_t dbm, const char *reason)
 
 static void ble_tx_power_stress(const char *reason)
 {
+    last_stress_ms = k_uptime_get();   // stress 발생 시각 기록 (복귀 판정 기준)
     (void)ble_set_conn_tx_power(BLE_TX_POWER_STRESS_DBM, reason);
 }
 
+// 마지막 stress 이후 충분히 조용하면(BLE_TX_RECOVER_HOLD_MS) NORMAL(4)로 복귀
+static void ble_tx_power_try_recover(void)
+{
+    if ((current_tx_power_dbm != BLE_TX_POWER_NORMAL_DBM) &&
+        ((k_uptime_get() - last_stress_ms) >= BLE_TX_RECOVER_HOLD_MS))
+    {
+        (void)ble_set_conn_tx_power(BLE_TX_POWER_NORMAL_DBM, "link-recovered");
+    }
+}
+
+// 컨트롤러에 설정된 현재 연결 TX power를 조회 (실제 적용값 확인용)
+static int ble_read_conn_tx_power(int8_t *dbm)
+{
+    struct net_buf *buf;
+    struct net_buf *rsp;
+    struct bt_hci_cp_vs_read_tx_power_level *cp;
+    struct bt_hci_rp_vs_read_tx_power_level *rp;
+    int err;
+
+    if (!current_conn_handle_valid || dbm == NULL)
+    {
+        return -ENOTCONN;
+    }
+
+    buf = bt_hci_cmd_alloc(K_NO_WAIT);
+    if (buf == NULL)
+    {
+        return -ENOBUFS;
+    }
+
+    cp = net_buf_add(buf, sizeof(*cp));
+    cp->handle_type = BT_HCI_VS_LL_HANDLE_TYPE_CONN;
+    cp->handle = sys_cpu_to_le16(current_conn_handle);
+
+    err = bt_hci_cmd_send_sync(BT_HCI_OP_VS_READ_TX_POWER_LEVEL, buf, &rsp);
+    if (err)
+    {
+        return err;
+    }
+
+    rp = (void *)rsp->data;
+    if (rp->status != 0U)
+    {
+        err = -EIO;
+    }
+    else
+    {
+        *dbm = rp->tx_power_level;
+    }
+
+    net_buf_unref(rsp);
+    return err;
+}
+
 static int ble_read_conn_rssi(int8_t *rssi)
 {
     struct net_buf *buf;
@@ -221,8 +278,10 @@ static void tx_power_monitor_handler(struct k_work *work)
         low_rssi_count = 0U;
     }
 
-    k_work_schedule(&tx_power_monitor_work,
-                    K_MSEC(BLE_RSSI_MONITOR_INTERVAL_MS));
+    // 전송이 없어도 주기적으로 복귀 판정 (마지막 stress 후 충분히 조용하면 NORMAL)
+    ble_tx_power_try_recover();
+
+    k_work_schedule(&tx_power_monitor_work, K_MSEC(BLE_RSSI_MONITOR_INTERVAL_MS));
 }
 
 static void ble_log_local_identity(void)
@@ -523,7 +582,7 @@ static const struct bt_data sd_dfu[] =
     BT_DATA_BYTES(BT_DATA_UUID128_SOME, SMP_BT_SVC_UUID_VAL),
 };
 
-/* Connection callbacks */
+/* BLE TX Power Control */
 static void connected(struct bt_conn *conn, uint8_t err)
 {
     if (err)
@@ -539,7 +598,25 @@ static void connected(struct bt_conn *conn, uint8_t err)
     current_tx_power_dbm = BLE_TX_POWER_NORMAL_DBM;
     low_rssi_count = 0U;
     slow_tx_count = 0U;
-    (void)ble_set_conn_tx_power(BLE_TX_POWER_NORMAL_DBM, "connected");
+    last_stress_ms = k_uptime_get();
+    
+    // 컨트롤러 기본 출력이 최대(+8)이므로, 연결 시 NORMAL(4)로 강제 적용
+    if (current_conn_handle_valid)
+    {
+        (void)ble_tx_power_write(BT_HCI_VS_LL_HANDLE_TYPE_CONN, current_conn_handle, BLE_TX_POWER_NORMAL_DBM, "connected");
+    }
+
+    int8_t cur_txp = 0;
+    int txp_ret = ble_read_conn_tx_power(&cur_txp);
+    if (txp_ret == 0)
+    {
+        DBG_CORE("[BLE] TX power (current) = %d dBm\r\n", cur_txp);
+    }
+    else
+    {
+        DBG_CORE("[BLE] TX power read fail ret=%d\r\n", txp_ret);
+    }
+
     if (BLE_RSSI_MONITOR_ENABLED)
     {
         k_work_schedule(&tx_power_monitor_work, K_MSEC(BLE_RSSI_MONITOR_INTERVAL_MS));
@@ -579,6 +656,7 @@ static void disconnected(struct bt_conn *conn, uint8_t reason)
     current_tx_power_dbm = BLE_TX_POWER_NORMAL_DBM;
     low_rssi_count = 0U;
     slow_tx_count = 0U;
+    last_stress_ms = 0;
 
     if (current_conn)
     {
@@ -792,6 +870,9 @@ int ble_advertising_start(void)
         return err;
     }
 
+    // 컨트롤러 기본 출력이 최대(+8)이므로, 광고는 항상 NORMAL(4)로 고정 (stress 무관)
+    (void)ble_tx_power_write(BT_HCI_VS_LL_HANDLE_TYPE_ADV, 0, BLE_TX_POWER_NORMAL_DBM, "adv");
+
     k_work_cancel_delayable(&adv_timeout_work);
     if (!advertising_unlimited)   // DFU 광고 포함, 미연결 10분 시 전원 OFF
     {
@@ -950,6 +1031,9 @@ int ble_data_send(const uint8_t *data, uint16_t len)
         else
         {
             slow_tx_count = 0U;
+
+            // 정상 전송 완료 → 마지막 stress 이후 충분히 조용했으면 복귀
+            ble_tx_power_try_recover();
         }
     }