[Bluetooth] filter name

Question

Hello,

I am programming BLE with the nRF52840-DK. [Toolchain Manager: v1.3.0, IDE: Visual Studio Code (VSCode), SDK: ncs v2.6.0 ]

I am trying to use the device name as a filter type.

However, even though DEVICE_NAME(peripheral: "SEONG") and FILTER(central: "SEONGMIN") are not exactly the same, they still get connected.Conversely, DEVICE_NAME(peripheral: "SEONG12") and FILTER(central: "SEONGMIN") do not connect. I am curious to know the reason behind this.

Additionally, I would like to understand the difference between 'BT_SCAN_FILTER_TYPE_NAME' and 'BT_SCAN_FILTER_TYPE_SHORT_NAME'.

prj.conf

#
# Copyright (c) 2018 Nordic Semiconductor
#
# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
#

# Enable the UART driver
CONFIG_UART_ASYNC_API=y
CONFIG_NRFX_UARTE0=y
CONFIG_SERIAL=y
CONFIG_CONSOLE=y
CONFIG_UART_CONSOLE=y

# Enable the BLE stack with GATT Client configuration
CONFIG_BT=y
CONFIG_BT_CENTRAL=y
CONFIG_BT_SMP=y
CONFIG_BT_GATT_CLIENT=y

# Enable the BLE modules from NCS
CONFIG_BT_NUS_CLIENT=y
CONFIG_BT_SCAN=y
CONFIG_BT_SCAN_FILTER_ENABLE=y
CONFIG_BT_SCAN_UUID_CNT=1
CONFIG_BT_GATT_DM=y
CONFIG_HEAP_MEM_POOL_SIZE=2048
CONFIG_BT_SCAN_NAME_CNT=5
CONFIG_BT_SCAN_NAME_MAX_LEN=20


# This example requires more stack
CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=2048
CONFIG_MAIN_STACK_SIZE=1536

# Enable bonding
CONFIG_BT_SETTINGS=y
CONFIG_FLASH=y
CONFIG_FLASH_PAGE_LAYOUT=y
CONFIG_FLASH_MAP=y
CONFIG_NVS=y
CONFIG_SETTINGS=y

# Config logger
CONFIG_LOG=y
CONFIG_USE_SEGGER_RTT=y
CONFIG_LOG_BACKEND_RTT=y
CONFIG_LOG_BACKEND_UART=n
CONFIG_LOG_PRINTK=n

CONFIG_ASSERT=y

central code

int err;
	struct bt_le_scan_param scan_param = { 
		.type = 0x01, //  1: active,  0: passive
 		.options = BT_LE_SCAN_OPT_FILTER_DUPLICATE,
		.interval = 0x0010, // 10ms
		.window = 0x0010, // 10ms
	};
	struct bt_scan_init_param scan_init = {
		.connect_if_match = 1,		
		.scan_param = &scan_param,    
		.conn_param = conn_param  
	};

	bt_scan_init(&scan_init);
	bt_scan_cb_register(&scan_cb);
 
	err = bt_scan_filter_add(BT_SCAN_FILTER_TYPE_NAME, "SEONGMIN"); //scan.c scan.h, nus.h
	if (err) {
		LOG_ERR("Scanning filters cannot be set (err %d)", err);
		return err;
	}

	err = bt_scan_filter_enable(BT_SCAN_NAME_FILTER, false); //scan.c scan.h
	if (err) {
		LOG_ERR("Filters cannot be turned on (err %d)", err);
		return err;
	}

peripheral code

#include <zephyr/bluetooth/conn.h>
#include <zephyr/sys/printk.h>
#include <zephyr/kernel.h>
#include <zephyr/settings/settings.h>
#include <zephyr/logging/log.h>
#include <zephyr/bluetooth/bluetooth.h>
#include <bluetooth/services/nus.h>
#define LOG_MODULE_NAME cho
LOG_MODULE_REGISTER(LOG_MODULE_NAME);
#define DEVICE_NAME "SEONG"
//#define DEVICE_NAME CONFIG_BT_DEVICE_NAME
#define DEVICE_NAME_LEN	(sizeof(DEVICE_NAME) - 1)

static struct bt_conn *auth_conn;
static K_SEM_DEFINE(ble_init_ok, 0, 1);
static const 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, DEVICE_NAME, DEVICE_NAME_LEN),
};
static const struct bt_data sd[] = {
	BT_DATA_BYTES(BT_DATA_UUID128_ALL, BT_UUID_NUS_VAL),
};

static void auth_passkey_display(struct bt_conn *conn, unsigned int passkey){
	char addr[BT_ADDR_LE_STR_LEN];
	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));
	printk("Passkey for %s: %06u", addr, passkey);
}

static void auth_passkey_confirm(struct bt_conn *conn, unsigned int passkey){
	char addr[BT_ADDR_LE_STR_LEN];
	auth_conn = bt_conn_ref(conn);
	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));
	printk("Passkey for %s: %06u", addr, passkey);
	printk("Press Button 1 to confirm, Button 2 to reject.");
}

static void auth_cancel(struct bt_conn *conn){
	char addr[BT_ADDR_LE_STR_LEN];
	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));
	printk("Pairing cancelled: %s", addr);
}

static struct bt_conn_auth_cb conn_auth_callbacks = {
	.passkey_display = auth_passkey_display,
	.passkey_confirm = auth_passkey_confirm,
	.cancel = auth_cancel,
};

static void pairing_complete(struct bt_conn *conn, bool bonded){
	char addr[BT_ADDR_LE_STR_LEN];
	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));
	printk("Pairing completed: %s, bonded: %d", addr, bonded);
}

static void pairing_failed(struct bt_conn *conn, enum bt_security_err reason){
	char addr[BT_ADDR_LE_STR_LEN];
	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));
	printk("Pairing failed conn: %s, reason %d", addr, reason);
}

static struct bt_conn_auth_info_cb conn_auth_info_callbacks = {
	.pairing_complete = pairing_complete,
	.pairing_failed = pairing_failed
};

int main(void){
	int err;
	printk("cho >> 240628_advv_peripheral\n");

	err = bt_conn_auth_cb_register(&conn_auth_callbacks);  //success: 0
	printk("bt_conn_auth_cb_register: %d\n",err);

	err = bt_conn_auth_info_cb_register(&conn_auth_info_callbacks); //success: 0
	printk("bt_conn_auth_info_cb_register: %d\n",err);

	err = bt_enable(NULL);
	printk("bt_enable\n");
	k_sem_give(&ble_init_ok);
	if (IS_ENABLED(CONFIG_SETTINGS)) {
		settings_load();
	}
	err = bt_le_adv_start(BT_LE_ADV_CONN, ad, ARRAY_SIZE(ad), sd, ARRAY_SIZE(sd));
	printk("bt_le_adv_start: %d\n",err);

}