nRF5340 LE disconnection Issue.

[AKV]

Hi,

We are using nRF5340 DK and the nRF Connect SDK Version 2.6.1.

We are experiencing an issue with disconnections. We use bt_conn_ref() when receiving the connected event and bt_conn_unref() when receiving the disconnection event.

However, sometimes after a disconnection, when we retry, we encounter the error: "bt_conn: bt_conn_exists_le: Found valid connection (0x20001a18) with address FF:F5:55:5A:D6:6A (random) in disconnected state".

Why does this issue occur even after the disconnection event has been processed?

If we call bt_conn_unref() twice during the disconnection event as shown in the below code (essentially incrementing once upon connection and decrementing twice upon disconnection), the issue does not occur.

void connected(struct bt_conn *conn, uint8_t conn_err){
	bt_conn_ref(conn);
}
void disconnected(struct bt_conn *conn, uint8_t reason){
 	bt_conn_unref(conn);
 	bt_conn_unref(conn);	
}

Could this behavior be due to an internal counter issue?

[Vidar Berg]

Hi,

Thanks for the additional information, In your application, are you calling the bt_gatt_exchange_mtu() to initiate the MTU exchange? This should only be called if there was no connection error. 

Could you post code code snippets to show how your connected and disconnected callbacks are implemented?

Best regards,

Vidar

[AKV]

Hi 

Thanks for the response.

Please find the attached connection make, connected event and disconnected event code portion

int ConnectToPeripheral(bt_addr_le_t *addr, uint16_t nodeId){

	int err;
	static struct bt_le_conn_param *param;
	static struct bt_conn_le_create_param *create_conn_param;
	bt_addr_le_t *deviceAddr = addr;
	param = BT_LE_CONN_PARAM_DEFAULT; 
	param->interval_max = CONN_INTERVAL_MAX;
	param->interval_min = CONN_INTERVAL_MIN;
	param->timeout = SUPERVISION_TIMEOUT;
	create_conn_param = BT_CONN_LE_CREATE_CONN;
	create_conn_param->timeout = 150;

    err = bt_le_scan_stop();
    if (err) {
        LOGT(ERROR,"Stop LE scan failed before connection (err %d)", err);				
    }else{
		scanActive=false;
	}

	err = bt_conn_le_create(deviceAddr, create_conn_param, param, &pending_central_conn);
	return err;
}

static void connected(struct bt_conn *conn, uint8_t conn_err)
{
	struct bt_conn_info info;
	char ConnectedAddr[BT_ADDR_LE_STR_LEN];
	int ret=0;

	bt_addr_le_to_str(bt_conn_get_dst(conn), ConnectedAddr, sizeof(ConnectedAddr));

	if (conn_err) {
		LOGT(ERROR,"Failed to connect to %s (%u)", ConnectedAddr, conn_err);
		bt_conn_unref(conn);		

		if(!scanActive){			 
        	discovery_State_Manage(SCANNING,FAST);    		
		}
		return;
	}	

	if (info.role == BT_CONN_ROLE_CENTRAL) {		
		update_le_parame(conn);		
	}

	if(info.role == BT_CONN_ROLE_PERIPHERAL){
		bt_conn_ref(conn);
	}  

}

static void disconnected(struct bt_conn *conn, uint8_t reason)
{	
	LOGT(CONN,"####### DISCONNECTED Reason: %d #######",reason);	

	if(conn){          
        bt_conn_unref(conn);
    }
	
}

static void update_le_parame(struct bt_conn *conn){

	int err;

	exchange_params.func = exchange_func;
	err = bt_gatt_exchange_mtu(conn, &exchange_params);
	if (err) {
		LOGT(ERROR,"MTU exchange failed (err %d)", err);
	}	

	err = bt_conn_le_phy_update(conn, conn_phy);
	if (err) {
		LOGT(ERROR,"PHY update failed: %d", err);
	}

}

[Vidar Berg]

Hi,

Thanks for the code. In the connected callback, it seems that you are using the 'info' variable without initializing it. I would have expected to see a call to the bt_conn_get_info() function to assign the connection information to the variable.

[AKV]

Hi,

Thanks for the response. 

The bt_conn_get_info() function is I'm already using. It was accidentally removed when I sent you my reply.

static void connected(struct bt_conn *conn, uint8_t conn_err)
{
	struct bt_conn_info info;
	char ConnectedAddr[BT_ADDR_LE_STR_LEN];
	int ret=0;

	bt_addr_le_to_str(bt_conn_get_dst(conn), ConnectedAddr, sizeof(ConnectedAddr));

	if (conn_err) {
		LOGT(ERROR,"Failed to connect to %s (%u)", ConnectedAddr, conn_err);
		bt_conn_unref(conn);		

		if(!scanActive){			 
        	discovery_State_Manage(SCANNING,FAST);    		
		}
		return;
	}	

    bt_conn_get_info(conn, &info);
    
	if (info.role == BT_CONN_ROLE_CENTRAL) {		
		update_le_parame(conn);		
	}

	if(info.role == BT_CONN_ROLE_PERIPHERAL){
		bt_conn_ref(conn);
	}  

}

[AKV]

Hi,

We encountered another critical disconnection issue during testing with just two devices.

Device A and device B are both in use. If device B is turned off, device A does not receive any disconnection event, even though device B is no longer on. we have notice that device A still shows device B as connected, even though device B is actually off. I verified this by removing the battery from device B to confirm that it was indeed powered down.

Could this be happening because a disconnection event is not being sent to the app core from net core?