refactor(split): allow central to define connection parameters

Fixes #1614

Author: xudongzheng

app/src/split/bluetooth/Kconfig

@@ -29,6 +29,18 @@ config ZMK_SPLIT_BLE_CENTRAL_SPLIT_RUN_QUEUE_SIZE
     int "Max number of behavior run events to queue to send to the peripheral(s)"
     default 5
 
+config ZMK_SPLIT_BLE_PREF_INT
+    int "Connection interval to use for split central/peripheral connection"
+    default 6
+
+config ZMK_SPLIT_BLE_PREF_LATENCY
+    int "Latency to use for split central/peripheral connection"
+    default 30
+
+config ZMK_SPLIT_BLE_PREF_TIMEOUT
+    int "Supervision timeout to use for split central/peripheral connection"
+    default 400
+
 endif # ZMK_SPLIT_ROLE_CENTRAL
 
 if !ZMK_SPLIT_ROLE_CENTRAL
@@ -54,8 +66,9 @@ config BT_MAX_PAIRED
 config BT_MAX_CONN
     default 1
 
-config BT_PERIPHERAL_PREF_MAX_INT
-    default 6
+# Allow central to specify connection parameters.
+config BT_GAP_AUTO_UPDATE_CONN_PARAMS
+    default n
 
 #!ZMK_SPLIT_ROLE_CENTRAL
 endif

app/src/split/bluetooth/central.c

@@ -408,7 +408,9 @@ static bool split_central_eir_found(struct bt_data *data, void *user_data) {
                     LOG_ERR("Update phy conn failed (err %d)", err);
                 }
             } else {
-                param = BT_LE_CONN_PARAM(0x0006, 0x0006, 30, 400);
+                param = BT_LE_CONN_PARAM(
+                    CONFIG_ZMK_SPLIT_BLE_PREF_INT, CONFIG_ZMK_BLE_SPLIT_PREF_INT,
+                    CONFIG_ZMK_SPLIT_BLE_PREF_LATENCY, CONFIG_ZMK_BLE_SPLIT_PREF_TIMEOUT);
 
                 LOG_DBG("Initiating new connnection");