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目录
概述
1 系统架构
2 代码结构详解
2.1 初始化代码结构
2.2 主循环函数
2.3 错误处理函数
3 代码介绍
3.1 初始化参数代码
3.2 BT_CONN_CB_DEFINE函数
3.2.1 remote_info_available_cb函数
3.2.2 connected_cb函数
3.2.3 disconnected_cb函数
3.3 bt_le_ext_adv_create函数
3.3.1 request_cb()函数
3.3.2 response_cb（）函数
3.4 bt_le_scan_start（）函数
3.4 bt_gatt_discover函数
3.5 bt_gatt_write函数
3.7 错误处理功能
4 源代码文件
5 系统测试
概述
本文介绍了基于Zephyr RTOS的蓝牙周期性广播系统架构与实现。系统采用三部分设计：初始化部分完成蓝牙连接接口、广播参数设置及启动功能；主循环实现设备发现、数据传输和GATT操作；错误处理模块管理连接状态。关键技术包括：通过bt_le_ext_adv_create创建广播接口，使用bt_le_per_adv_start启动周期性广播，利用信号量机制(sem_connected/sem_disconnected)监控连接状态，并实现GATT数据写入(bt_gatt_write)和特征发现(bt_gatt_discover)功能。系统通过request_cb和response_cb回调函数处理广播数据请求与响应，支持多子事件和响应时隙配置，适用于需要低功耗周期性数据传输的物联网场景。
1 系统架构
系统分的软件设计分为3个部分：
-1）Initial（）： 蓝牙连接接口函数，广播相关函数初始化，启动广播功能
-2） while(1){}： 主循环函数，实现发现BLE设备，设置传输的信息，GATT功能
-3）错误处理部分
2 代码结构详解
2.1 初始化代码结构
1） BT_CONN_CB_DEFINE，定义蓝牙连接相关的回调函数
2） init_bufs， 初始化发送的数据
3）bt_le_ext_adv_create()， 创建广播接口
4）bt_le_per_adv_set_param（），设置广播参数
5）bt_le_per_adv_start（），启动周期广播函数
6）bt_le_ext_adv_start（）， 使能扩展广播功能
2.2 主循环函数
1）bt_le_scan_start（），开启连续扫描功能
2）k_sem_take(&sem_connected, K_FOREVER)，监测蓝牙连接状态
3）bt_le_per_adv_set_info_transfer（），设置广播数据传输
4）bt_gatt_discover（），发现GATT设备
5） k_sem_take(&sem_discovered, K_SECONDS(10))， 监测设备连接的信号量
6）bt_gatt_write（）,GATT方式写数据
7）k_sem_take(&sem_written, K_SECONDS(10));监测写数据是否完成
2.3 错误处理函数
1）bt_conn_disconnect（）， 断开蓝牙连接
2） k_sem_take(&sem_disconnected, K_FOREVER); 监测断开蓝牙设备连接的信号量
3 代码介绍
3.1 初始化参数代码
代码13~16行：定义基本参数
代码18~21行： 定义系统中使用的信号量
代码23行：定义系统的UUID参数
代码28~37行： 定义广播的参数
3.2 BT_CONN_CB_DEFINE函数
3.2.1 remote_info_available_cb函数
代码第130行：发送BLE连接的信号量
3.2.2 connected_cb函数
3.2.3 disconnected_cb函数
3.3 bt_le_ext_adv_create函数
该函数主要调用request_cb和response_cb函数
3.3.1 request_cb()函数
代码56~65函数：填充数据参数
代码67行：设置广播的数据
3.3.2 response_cb（）函数
代码96行： 解析收到的广播数据
3.4 bt_le_scan_start（）函数
代码271函数：在bt_le_scan_start函数中调用device_found
device_found函数的内容：
代码173行： 调用data_cb解析数据
代码179行： 停止BLE
代码183行：重新创建连接
data_cb函数的内容
3.4 bt_gatt_discover函数
代码321行：注册discover_func函数
代码325行： 调用bt_gatt_discover函数，执行数据处理
discover_func函数的内容
3.5 bt_gatt_write函数
代码351行：调用bt_gatt_write，执行写数据功能
代码361行：等待写数据完成
3.7 错误处理功能
代码378行： 断开蓝牙连接功能
代码383行： 获取BT断开的信号量
4 源代码文件
/** Copyright (c) 2023 Nordic Semiconductor ASA** SPDX-License-Identifier: Apache-2.0*/#include <zephyr/bluetooth/att.h>
#include <zephyr/bluetooth/bluetooth.h>
#include <zephyr/bluetooth/conn.h>
#include <zephyr/bluetooth/gatt.h>
#include <zephyr/bluetooth/hci.h>#define NUM_RSP_SLOTS 5
#define NUM_SUBEVENTS 5
#define PACKET_SIZE 5
#define NAME_LEN 30static K_SEM_DEFINE(sem_connected, 0, 1);
static K_SEM_DEFINE(sem_discovered, 0, 1);
static K_SEM_DEFINE(sem_written, 0, 1);
static K_SEM_DEFINE(sem_disconnected, 0, 1);static struct bt_uuid_128 pawr_char_uuid =BT_UUID_INIT_128(BT_UUID_128_ENCODE(0x12345678, 0x1234, 0x5678, 0x1234, 0x56789abcdef1));static uint16_t pawr_attr_handle;static const struct bt_le_per_adv_param per_adv_params = {.interval_min = 0xFF,.interval_max = 0xFF,.options = 0,.num_subevents = NUM_SUBEVENTS,.subevent_interval = 0x30,.response_slot_delay = 0x5,.response_slot_spacing = 0x50,.num_response_slots = NUM_RSP_SLOTS,
};static struct bt_le_per_adv_subevent_data_params subevent_data_params[NUM_SUBEVENTS];
static struct net_buf_simple bufs[NUM_SUBEVENTS];
static uint8_t backing_store[NUM_SUBEVENTS][PACKET_SIZE];BUILD_ASSERT(ARRAY_SIZE(bufs) == ARRAY_SIZE(subevent_data_params));
BUILD_ASSERT(ARRAY_SIZE(backing_store) == ARRAY_SIZE(subevent_data_params));static uint8_t counter;static void request_cb(struct bt_le_ext_adv *adv, const struct bt_le_per_adv_data_request *request)
{int err;uint8_t to_send;struct net_buf_simple *buf;to_send = MIN(request->count, ARRAY_SIZE(subevent_data_params));for (size_t i = 0; i < to_send; i++) {buf = &bufs[i];buf->data[buf->len - 1] = counter++;subevent_data_params[i].subevent =(request->start + i) % per_adv_params.num_subevents;subevent_data_params[i].response_slot_start = 0;subevent_data_params[i].response_slot_count = NUM_RSP_SLOTS;subevent_data_params[i].data = buf;}err = bt_le_per_adv_set_subevent_data(adv, to_send, subevent_data_params);if (err) {printk("Failed to set subevent data (err %d)\n", err);} else {printk("Subevent data set %d\n", counter);}
}static bool print_ad_field(struct bt_data *data, void *user_data)
{ARG_UNUSED(user_data);printk(" 0x%02X: ", data->type);for (size_t i = 0; i < data->data_len; i++) {printk("%02X", data->data[i]);}printk("\n");return true;
}static struct bt_conn *default_conn;static void response_cb(struct bt_le_ext_adv *adv, struct bt_le_per_adv_response_info *info,struct net_buf_simple *buf)
{if (buf) {printk("Response: subevent %d, slot %d\n", info->subevent, info->response_slot);bt_data_parse(buf, print_ad_field, NULL);}
}static const struct bt_le_ext_adv_cb adv_cb = {.pawr_data_request = request_cb,.pawr_response = response_cb,
};void connected_cb(struct bt_conn *conn, uint8_t err)
{printk("Connected (err 0x%02X)\n", err);__ASSERT(conn == default_conn, "Unexpected connected callback");if (err) {bt_conn_unref(default_conn);default_conn = NULL;}
}void disconnected_cb(struct bt_conn *conn, uint8_t reason)
{printk("Disconnected, reason 0x%02X %s\n", reason, bt_hci_err_to_str(reason));bt_conn_unref(default_conn);default_conn = NULL;k_sem_give(&sem_disconnected);
}void remote_info_available_cb(struct bt_conn *conn, struct bt_conn_remote_info *remote_info)
{/* Need to wait for remote info before initiating PAST */k_sem_give(&sem_connected);
}BT_CONN_CB_DEFINE(conn_cb) = {.connected = connected_cb,.disconnected = disconnected_cb,.remote_info_available = remote_info_available_cb,
};static bool data_cb(struct bt_data *data, void *user_data)
{char *name = user_data;uint8_t len;switch (data->type) {case BT_DATA_NAME_SHORTENED:case BT_DATA_NAME_COMPLETE:len = MIN(data->data_len, NAME_LEN - 1);memcpy(name, data->data, len);name[len] = '\0';return false;default:return true;}
}static void device_found(const bt_addr_le_t *addr, int8_t rssi, uint8_t type,struct net_buf_simple *ad)
{char addr_str[BT_ADDR_LE_STR_LEN];char name[NAME_LEN];int err;if (default_conn) {return;}/* We're only interested in connectable events */if (type != BT_GAP_ADV_TYPE_ADV_IND && type != BT_GAP_ADV_TYPE_ADV_DIRECT_IND) {return;}(void)memset(name, 0, sizeof(name));bt_data_parse(ad, data_cb, name);if (strcmp(name, "PAwR sync sample")) {return;}if (bt_le_scan_stop()) {return;}err = bt_conn_le_create(addr, BT_CONN_LE_CREATE_CONN, BT_LE_CONN_PARAM_DEFAULT,&default_conn);if (err) {printk("Create conn to %s failed (%u)\n", addr_str, err);}
}static uint8_t discover_func(struct bt_conn *conn, const struct bt_gatt_attr *attr,struct bt_gatt_discover_params *params)
{struct bt_gatt_chrc *chrc;char str[BT_UUID_STR_LEN];printk("Discovery: attr %p\n", attr);if (!attr) {return BT_GATT_ITER_STOP;}chrc = (struct bt_gatt_chrc *)attr->user_data;bt_uuid_to_str(chrc->uuid, str, sizeof(str));printk("UUID %s\n", str);if (!bt_uuid_cmp(chrc->uuid, &pawr_char_uuid.uuid)) {pawr_attr_handle = chrc->value_handle;printk("Characteristic handle: %d\n", pawr_attr_handle);k_sem_give(&sem_discovered);}return BT_GATT_ITER_STOP;
}static void write_func(struct bt_conn *conn, uint8_t err, struct bt_gatt_write_params *params)
{if (err) {printk("Write failed (err %d)\n", err);return;}k_sem_give(&sem_written);
}void init_bufs(void)
{for (size_t i = 0; i < ARRAY_SIZE(backing_store); i++) {backing_store[i][0] = ARRAY_SIZE(backing_store[i]) - 1;backing_store[i][1] = BT_DATA_MANUFACTURER_DATA;backing_store[i][2] = 0x59; /* Nordic */backing_store[i][3] = 0x00;net_buf_simple_init_with_data(&bufs[i], &backing_store[i],ARRAY_SIZE(backing_store[i]));}
}#define MAX_SYNCS (NUM_SUBEVENTS * NUM_RSP_SLOTS)
struct pawr_timing {uint8_t subevent;uint8_t response_slot;
} __packed;static uint8_t num_synced;int main(void)
{int err;struct bt_le_ext_adv *pawr_adv;struct bt_gatt_discover_params discover_params;struct bt_gatt_write_params write_params;struct pawr_timing sync_config;init_bufs();printk("Starting Periodic Advertising Demo\n");/* Initialize the Bluetooth Subsystem */err = bt_enable(NULL);if (err) {printk("Bluetooth init failed (err %d)\n", err);return 0;}/* Create a non-connectable advertising set */err = bt_le_ext_adv_create(BT_LE_EXT_ADV_NCONN, &adv_cb, &pawr_adv);if (err) {printk("Failed to create advertising set (err %d)\n", err);return 0;}/* Set periodic advertising parameters */err = bt_le_per_adv_set_param(pawr_adv, &per_adv_params);if (err) {printk("Failed to set periodic advertising parameters (err %d)\n", err);return 0;}/* Enable Periodic Advertising */printk("Start Periodic Advertising\n");err = bt_le_per_adv_start(pawr_adv);if (err) {printk("Failed to enable periodic advertising (err %d)\n", err);return 0;}printk("Start Extended Advertising\n");err = bt_le_ext_adv_start(pawr_adv, BT_LE_EXT_ADV_START_DEFAULT);if (err) {printk("Failed to start extended advertising (err %d)\n", err);return 0;}while (num_synced < MAX_SYNCS) {/* Enable continuous scanning */err = bt_le_scan_start(BT_LE_SCAN_PASSIVE_CONTINUOUS, device_found);if (err) {printk("Scanning failed to start (err %d)\n", err);return 0;}printk("Scanning successfully started\n");k_sem_take(&sem_connected, K_FOREVER);err = bt_le_per_adv_set_info_transfer(pawr_adv, default_conn, 0);if (err) {printk("Failed to send PAST (err %d)\n", err);goto disconnect;}printk("PAST sent\n");discover_params.uuid = &pawr_char_uuid.uuid;discover_params.func = discover_func;discover_params.start_handle = BT_ATT_FIRST_ATTRIBUTE_HANDLE;discover_params.end_handle = BT_ATT_LAST_ATTRIBUTE_HANDLE;discover_params.type = BT_GATT_DISCOVER_CHARACTERISTIC;err = bt_gatt_discover(default_conn, &discover_params);if (err) {printk("Discovery failed (err %d)\n", err);goto disconnect;}printk("Discovery started\n");err = k_sem_take(&sem_discovered, K_SECONDS(10));if (err) {printk("Timed out during GATT discovery\n");goto disconnect;}sync_config.subevent = num_synced % NUM_SUBEVENTS;sync_config.response_slot = num_synced / NUM_RSP_SLOTS;num_synced++;write_params.func = write_func;write_params.handle = pawr_attr_handle;write_params.offset = 0;write_params.data = &sync_config;write_params.length = sizeof(sync_config);err = bt_gatt_write(default_conn, &write_params);if (err) {printk("Write failed (err %d)\n", err);num_synced--;goto disconnect;}printk("Write started\n");err = k_sem_take(&sem_written, K_SECONDS(10));if (err) {printk("Timed out during GATT write\n");num_synced--;goto disconnect;}printk("PAwR config written to sync %d, disconnecting\n", num_synced - 1);disconnect:/* Adding delay (2ms * interval value, using 2ms intead of the 1.25ms* used by controller) to ensure sync is established before* disconnection.*/k_sleep(K_MSEC(per_adv_params.interval_max * 2));err = bt_conn_disconnect(default_conn, BT_HCI_ERR_REMOTE_USER_TERM_CONN);if (err) {return 0;}k_sem_take(&sem_disconnected, K_FOREVER);}printk("Maximum numnber of syncs onboarded\n");while (true) {k_sleep(K_SECONDS(1));}return 0;
}
5 系统测试
编译代码下载至nRFDK-52832板卡中，运行结构如下：
