samples: bluetooth: Add sample demonstrating direct advertising

This sample shows how to run BLE direct advertising towards central
with enabled privacy.

Signed-off-by: Michal morsisko <morsisko@gmail.com>

samples/bluetooth/direct_adv/CMakeLists.txt

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+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(direct_adv)
+
+target_sources(app PRIVATE
+  src/main.c
+)

samples/bluetooth/direct_adv/README.rst

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+.. _ble_direct_adv:
+
+Bluetooth: Direct Advertising
+#############################
+
+Overview
+********
+
+Application demonstrating the BLE Direct Advertising capability. If no device is bonded
+to the peripheral, casual advertising will be performed. Once bonded, on every subsequent
+boot direct advertising to the bonded central will be performed. Additionally this sample
+provides two BLE characteristics. To perform write, devices need to be bonded, while read
+can be done just after connection (no bonding required).
+
+Please note that direct advertising towards iOS based devices is not allowed.
+For more information about designing BLE devices for Apple products refer to
+"Accessory Design Guidelines for Apple Devices".
+
+Requirements
+************
+
+* A board with BLE support
+* Second BLE device acting as a central with enabled privacy. For example another Zephyr board
+  or any modern smartphone
+
+Building and Running
+********************
+
+This sample can be found under :zephyr_file:`samples/bluetooth/direct_adv` in the
+Zephyr tree.
+
+See :ref:`bluetooth samples section <bluetooth-samples>` for details.

samples/bluetooth/direct_adv/prj.conf

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+# Increased stack due to settings API usage
+CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=2048
+
+CONFIG_BT=y
+CONFIG_BT_DEBUG_LOG=y
+CONFIG_BT_SMP=y
+CONFIG_BT_SIGNING=y
+CONFIG_BT_PERIPHERAL=y
+CONFIG_BT_DIS=y
+CONFIG_BT_ATT_PREPARE_COUNT=1
+CONFIG_BT_PRIVACY=y
+CONFIG_BT_DEVICE_NAME="Direct Adv"
+CONFIG_BT_DEVICE_APPEARANCE=833
+
+CONFIG_BT_KEYS_OVERWRITE_OLDEST=y
+CONFIG_BT_SETTINGS=y
+CONFIG_FLASH=y
+CONFIG_FLASH_PAGE_LAYOUT=y
+CONFIG_FLASH_MAP=y
+CONFIG_NVS=y
+CONFIG_SETTINGS=y
+CONFIG_REBOOT=y

samples/bluetooth/direct_adv/sample.yaml

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+sample:
+  name: Bluetooh Direct Advertising
+tests:
+  sample.bluetooth.direct_adv:
+    harness: bluetooth
+    platform_allow: qemu_cortex_m3 qemu_x86
+    tags: bluetooth

samples/bluetooth/direct_adv/src/main.c

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+/*
+ * Copyright (c) 2022 Michal Morsisko
+ * Copyright (c) 2015-2016 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/types.h>
+#include <stddef.h>
+#include <string.h>
+#include <errno.h>
+#include <zephyr/sys/printk.h>
+#include <zephyr/sys/byteorder.h>
+#include <zephyr/sys/reboot.h>
+#include <zephyr/settings/settings.h>
+#include <zephyr/bluetooth/bluetooth.h>
+#include <zephyr/bluetooth/hci.h>
+#include <zephyr/bluetooth/conn.h>
+#include <zephyr/bluetooth/uuid.h>
+#include <zephyr/bluetooth/gatt.h>
+
+/* Custom Service Variables */
+#define BT_UUID_CUSTOM_SERVICE_VAL \
+	BT_UUID_128_ENCODE(0x12345678, 0x1234, 0x5678, 0x1234, 0x56789abcdef0)
+
+static struct bt_uuid_128 primary_service_uuid = BT_UUID_INIT_128(
+	BT_UUID_CUSTOM_SERVICE_VAL);
+
+static struct bt_uuid_128 read_characteristic_uuid = BT_UUID_INIT_128(
+	BT_UUID_128_ENCODE(0x12345678, 0x1234, 0x5678, 0x1234, 0x56789abcdef1));
+
+static struct bt_uuid_128 write_characteristic_uuid = BT_UUID_INIT_128(
+	BT_UUID_128_ENCODE(0x12345678, 0x1234, 0x5678, 0x1234, 0x56789abcdef2));
+
+static int signed_value;
+static struct bt_le_adv_param adv_param;
+static bt_addr_le_t bond_addr;
+
+static ssize_t read_signed(struct bt_conn *conn, const struct bt_gatt_attr *attr,
+			   void *buf, uint16_t len, uint16_t offset)
+{
+	int *value = &signed_value;
+
+	return bt_gatt_attr_read(conn, attr, buf, len, offset, value,
+				 sizeof(signed_value));
+}
+
+static ssize_t write_signed(struct bt_conn *conn, const struct bt_gatt_attr *attr,
+			    const void *buf, uint16_t len, uint16_t offset,
+			    uint8_t flags)
+{
+	int *value = &signed_value;
+
+	if (offset + len > sizeof(signed_value)) {
+		return BT_GATT_ERR(BT_ATT_ERR_INVALID_OFFSET);
+	}
+
+	memcpy(value + offset, buf, len);
+
+	return len;
+}
+
+/* Vendor Primary Service Declaration */
+BT_GATT_SERVICE_DEFINE(primary_service,
+	BT_GATT_PRIMARY_SERVICE(&primary_service_uuid),
+	BT_GATT_CHARACTERISTIC(&read_characteristic_uuid.uuid,
+			       BT_GATT_CHRC_READ,
+			       BT_GATT_PERM_READ,
+			       read_signed, NULL, NULL),
+	BT_GATT_CHARACTERISTIC(&write_characteristic_uuid.uuid,
+			       BT_GATT_CHRC_WRITE,
+			       BT_GATT_PERM_WRITE_ENCRYPT,
+			       NULL, write_signed, NULL),
+);
+
+static const struct bt_data ad[] = {
+	BT_DATA_BYTES(BT_DATA_FLAGS, (BT_LE_AD_GENERAL | BT_LE_AD_NO_BREDR)),
+	BT_DATA_BYTES(BT_DATA_UUID128_ALL, BT_UUID_CUSTOM_SERVICE_VAL),
+};
+
+static void connected(struct bt_conn *conn, uint8_t err)
+{
+	if (err) {
+		printk("Connection failed (err 0x%02x)\n", err);
+	} else {
+		printk("Connected\n");
+	}
+}
+
+static void disconnected(struct bt_conn *conn, uint8_t reason)
+{
+	printk("Disconnected (reason 0x%02x)\n", reason);
+}
+
+BT_CONN_CB_DEFINE(conn_callbacks) = {
+	.connected = connected,
+	.disconnected = disconnected
+};
+
+static void copy_last_bonded_addr(const struct bt_bond_info *info, void *data)
+{
+	bt_addr_le_copy(&bond_addr, &info->addr);
+}
+
+static void bt_ready(void)
+{
+	int err;
+	char addr[BT_ADDR_LE_STR_LEN];
+
+	printk("Bluetooth initialized\n");
+
+	if (IS_ENABLED(CONFIG_SETTINGS)) {
+		settings_load();
+	}
+
+	bt_addr_le_copy(&bond_addr, BT_ADDR_LE_NONE);
+	bt_foreach_bond(BT_ID_DEFAULT, copy_last_bonded_addr, NULL);
+
+	/* Address is equal to BT_ADDR_LE_NONE if compare returns 0.
+	 * This means there is no bond yet.
+	 */
+	if (bt_addr_le_cmp(&bond_addr, BT_ADDR_LE_NONE) != 0) {
+		bt_addr_le_to_str(&bond_addr, addr, sizeof(addr));
+		printk("Direct advertising to %s\n", addr);
+
+		adv_param = *BT_LE_ADV_CONN_DIR_LOW_DUTY(&bond_addr);
+		adv_param.options |= BT_LE_ADV_OPT_DIR_ADDR_RPA;
+		err = bt_le_adv_start(&adv_param, NULL, 0, NULL, 0);
+	} else {
+		err = bt_le_adv_start(BT_LE_ADV_CONN_NAME, ad, ARRAY_SIZE(ad), NULL, 0);
+	}
+
+	if (err) {
+		printk("Advertising failed to start (err %d)\n", err);
+	} else {
+		printk("Advertising successfully started\n");
+	}
+}
+
+void pairing_complete(struct bt_conn *conn, bool bonded)
+{
+	printk("Pairing completed. Rebooting in 5 seconds...\n");
+
+	k_sleep(K_SECONDS(5));
+	sys_reboot(SYS_REBOOT_WARM);
+}
+
+static struct bt_conn_auth_info_cb bt_conn_auth_info = {
+	.pairing_complete = pairing_complete
+};
+
+void main(void)
+{
+	int err;
+
+	err = bt_enable(NULL);
+	if (err) {
+		printk("Bluetooth init failed (err %d)\n", err);
+		return;
+	}
+
+	bt_ready();
+	bt_conn_auth_info_cb_register(&bt_conn_auth_info);
+
+	while (1) {
+		k_sleep(K_FOREVER);
+	}
+}