BLE not connecting after disconnect

[Zugislav]

I have a problem with connecting to my device after i disconnect from it.

I have tried ubond function, it does not work.

This is my disconnect function:

/*
	@brief callback function when BT connection is disconnected
*/
static void disconnected(struct bt_conn *conn, uint8_t reason)
{
	char addr[BT_ADDR_LE_STR_LEN];

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

	LOG_INF("Disconnected: %s, reason 0x%02x %s", addr, reason, bt_hci_err_to_str(reason));

	if (auth_conn) {
		bt_conn_unref(auth_conn);
		auth_conn = NULL;
	}

	if (current_conn) {
		bt_conn_unref(current_conn);
		current_conn = NULL;
	}
	
	advertising_stop();
	advertising_start();
}

I have a service with 2 characteristics and one configuration

        BT_GATT_CCC(rx_ccc_cfg_changed, BT_GATT_PERM_READ | BT_GATT_PERM_WRITE),

this is just for disable/enable notifications function.


I use nrf connect application on my mobile phone, and i connect to it, but after disconnecting i cannot again connect to the device.

Also adding advertising data:

// Declaring the advertising data
struct bt_data ad[] = {
	BT_DATA_BYTES(BT_DATA_FLAGS, (BT_LE_AD_GENERAL | BT_LE_AD_NO_BREDR)),
	BT_DATA(BT_DATA_NAME_COMPLETE, ble_dev_name, 16),
};

// Declaring the scanning data
struct bt_data sd[] = {
	BT_DATA(BT_DATA_UUID128_ALL, uuid_128, sizeof(uuid_128)),
	BT_DATA(BT_DATA_MANUFACTURER_DATA, manufacturer_data, sizeof(manufacturer_data))
};

// Declaring advertising parameters
static struct bt_le_adv_param adv_param = 
{
	.options = BT_LE_ADV_OPT_CONNECTABLE | BT_LE_ADV_OPT_USE_IDENTITY, 	/* Connectable advertising and use identity address */
	.interval_max = BT_GAP_ADV_FAST_INT_MAX_1,							/* 0x30 units, 48 units, 30ms */
	.interval_min = BT_GAP_ADV_FAST_INT_MIN_1,							/* 0x60 units, 96 units, 60ms */
	.peer = NULL														/* Set to NULL for undirected advertising */
};

I am using 2.9 version of nrf connect for vscode.

[Vidar Berg]

Hello,

Does the device start connectable advertising again after the disconnect?  In other words, if you restart scanning in the nRF Connect app after the disconnect, can you still discover your device? 

Best regards,

Vidar

[Zugislav]

no, i cannot discover my device on application. 

[Vidar Berg]

This indicates that the advertiser is not re-started on disconnect. Please also post your implementation of advertising_start().

[Zugislav]

// Declaring advertising parameters
static struct bt_le_adv_param adv_param = 
{
	.options = BT_LE_ADV_OPT_CONNECTABLE | BT_LE_ADV_OPT_USE_IDENTITY, 	/* Connectable advertising and use identity address */
	.interval_max = BT_GAP_ADV_FAST_INT_MAX_1,							/* 0x30 units, 48 units, 30ms */
	.interval_min = BT_GAP_ADV_FAST_INT_MIN_1,							/* 0x60 units, 96 units, 60ms */
	.peer = NULL														/* Set to NULL for undirected advertising */
};

// Declaring the advertising data
struct bt_data ad[] = {
	BT_DATA_BYTES(BT_DATA_FLAGS, (BT_LE_AD_GENERAL | BT_LE_AD_NO_BREDR)),
	BT_DATA(BT_DATA_NAME_COMPLETE, ble_dev_name, 16),
};

// Declaring the scanning data
struct bt_data sd[] = {
	BT_DATA(BT_DATA_UUID128_ALL, uuid_128, sizeof(uuid_128)),
	BT_DATA(BT_DATA_MANUFACTURER_DATA, manufacturer_data, sizeof(manufacturer_data))
};

/*
	@brief Function for starting advertising.
*/
void advertising_start(void)
{
	if(ble_status == BLE_IDLE){
		int err = bt_le_adv_start(&adv_param, ad, ARRAY_SIZE(ad), sd,
					ARRAY_SIZE(sd));
		
		if (err) {
			LOG_ERR("Advertising failed to start (err %d)", err);
		}
		ble_status = BLE_ADV;
	}
}

[Vidar Berg]

When the connectable advertiser was started with bt_le_adv_start(), the bt host will automatically try to resume advertising on disconnect as you don't have the BT_LE_ADV_OPT_ONE_TIME flag set.

Removing the call to  advertising_stop(); and advertising_start(); in disconnected() should fix the issue you are seeing with the advetiser not starting after disconnect.

[Zugislav]

i still doesnt work after i removed it.

i accidentaly put it closed, maybe for someone it works.

[Vidar Berg]

Can you upload a minimal version of your project here or in a private ticket so I can reproduce the problem and debug the problem on my end?

[Zugislav]

ill make some changes and upload it to a private ticket.

[Vidar Berg]

Thanks for sharing the code. The issue was that you were increasing the reference count for the connection object with '2' in your connected callback, but you only released one of them in your disconnected callback. The advertiser does not resume until the reference count is 0. Solution is to only call bt_conn_ref() once. 

You also had an endless loop in main() in the code you provided me. This will block other threads such as the logger thread.