nrf52 - 快速广播与慢速广播
许多应用都对功耗有严格要求，而且会要求一直处于广播模式，这时就要考虑降低广播频率来降低功耗，此时可以称为慢速广播，但是广播频率越快越利于手机连接，所以为了快速发现和连接，往往需要快速广播，一般的处理方式是快速广播30s然后进入慢速广播。
nordic考虑到了这种应用场景，所以用nordic的sdk很容易实现上述方案：
首先介绍一下广播参数的结构体：
typedef struct
{
bool ble_adv_whitelist_enabled; /**< Enable or disable use of the whitelist. */
bool ble_adv_directed_enabled; /**< Enable or disable direct advertising mode. */
bool ble_adv_directed_slow_enabled; /**< Enable or disable direct advertising mode. */
uint32_t ble_adv_directed_slow_interval; /**< Advertising interval for directed advertising. */
uint32_t ble_adv_directed_slow_timeout; /**< Time-out (number of tries) for direct advertising. */
bool ble_adv_fast_enabled; /**< Enable or disable fast advertising mode. */
uint32_t ble_adv_fast_interval; /**< Advertising interval for fast advertising. */
uint32_t ble_adv_fast_timeout; /**< Time-out (in seconds) for fast advertising. */
bool ble_adv_slow_enabled; /**< Enable or disable slow advertising mode. */
uint32_t ble_adv_slow_interval; /**< Advertising interval for slow advertising. */
uint32_t ble_adv_slow_timeout; /**< Time-out (in seconds) for slow advertising. */
}ble_adv_modes_config_t;
注释写的很清楚，前面有广播白名单、定向广播的设置，我们一般应用都是普通广播模式，所以重点看以下几个结构体成员
bool ble_adv_fast_enabled; /**< Enable or disable fast advertising mode. */
uint32_t ble_adv_fast_interval; /**< Advertising interval for fast advertising. */
uint32_t ble_adv_fast_timeout; /**< Time-out (in seconds) for fast advertising. */
bool ble_adv_slow_enabled; /**< Enable or disable slow advertising mode. */
uint32_t ble_adv_slow_interval; /**< Advertising interval for slow advertising. */
uint32_t ble_adv_slow_timeout; /**< Time-out (in seconds) for slow advertising. */前面三个是快速广播使能，以及广播间隔和广播时间，后面三个是慢速广播的
快速广播使能后，开始广播的时候选择快速模式就会进入快速广播模式，如果timeout设置非0，则时间到了timeout后退出快速广播模式，
此时如果慢速广播使能了，则进入慢速广播模式，如果timeout设置非0，则时间到了timeout后不再进行广播，
timeout设置为0则不退出当前广播模式，持续广播
了解了这个结构体，想必怎么实现开头说的方案就很简单了，下面贴一下具体实现代码：
1、相关宏定义
#define APP_ADV_FAST_INTERVAL 0x0028 /**< Fast advertising interval (in units of 0.625 ms.). */
#define APP_ADV_SLOW_INTERVAL 0x0C80 /**< Slow advertising interval (in units of 0.625 ms. ). */
#define APP_ADV_FAST_TIMEOUT 30 /**< The duration of the fast advertising period (in seconds). */
#define APP_ADV_SLOW_TIMEOUT 0 2、广播初始化函数
static void advertising_init(void)
{
uint32_t err_code;
ble_advdata_t advdata;
// Build advertising data struct to pass into @ref ble_advertising_init.
memset(&advdata, 0, sizeof(advdata));
advdata.name_type = BLE_ADVDATA_FULL_NAME;
advdata.include_appearance = true;
advdata.flags = BLE_GAP_ADV_FLAGS_LE_ONLY_GENERAL_DISC_MODE;
advdata.uuids_complete.uuid_cnt = sizeof(m_adv_uuids) / sizeof(m_adv_uuids[0]);
advdata.uuids_complete.p_uuids = m_adv_uuids;
//ble_adv_modes_config_t options = {0};
//options.ble_adv_fast_enabled = BLE_ADV_FAST_ENABLED;
//options.ble_adv_fast_interval = APP_ADV_INTERVAL;
//options.ble_adv_fast_timeout = APP_ADV_TIMEOUT_IN_SECONDS;
ble_adv_modes_config_t options =
{
BLE_ADV_WHITELIST_DISABLED,
BLE_ADV_DIRECTED_DISABLED,
BLE_ADV_DIRECTED_SLOW_DISABLED, 0,0,
BLE_ADV_FAST_ENABLED, APP_ADV_FAST_INTERVAL, APP_ADV_FAST_TIMEOUT,
BLE_ADV_SLOW_ENABLED, APP_ADV_SLOW_INTERVAL, APP_ADV_SLOW_TIMEOUT
};
err_code = ble_advertising_init(&advdata, NULL, &options, on_adv_evt, NULL);
APP_ERROR_CHECK(err_code);
}
ble_advertising_start(BLE_ADV_MODE_FAST);