低功耗蓝牙4.0BLE编程-nrf51822开发(2)

    首先看的示例是心率计一个示例程序：<KEIL path> \ARM\Device\Nordic\nrf51822\Board\pca10001\s110\ble_app_hrs\arm。

    打开工程前需要下载蓝牙协议栈S110 nRF51822 SoftDevice（s110_nrf51822_6.0.0_softdevice.hex）到板子中，这个手册上有说明。

    首先看的是main.c中的main函数：

/*****************************************************************************
* Main Function
*****************************************************************************/

/**@brief Function for the application main entry.
 */
int main(void)
{
    uint32_t err_code;

    timers_init();
    gpiote_init();
    buttons_init();
    ble_stack_init();
    bond_manager_init();

    // Initialize Bluetooth Stack parameters
    gap_params_init();
    advertising_init();
    services_init();
    conn_params_init();
    sec_params_init();

    // Start advertising
    advertising_start();

    // Enter main loop
    for (;;)
    {
        // Switch to a low power state until an event is available for the application
        err_code = sd_app_evt_wait();
        APP_ERROR_CHECK(err_code);
    }
}

它很简洁：初始化->start->loop。

(1)Timer初始化

/**@brief Function for the Timer initialization.
 *
* @details Initializes the timer module. This creates and starts application timers.
*/
static void timers_init(void)
{
    uint32_t err_code;

    // Initialize timer module
    APP_TIMER_INIT(APP_TIMER_PRESCALER, APP_TIMER_MAX_TIMERS, APP_TIMER_OP_QUEUE_SIZE, false);

    // Create timers
    err_code = app_timer_create(&m_battery_timer_id,
                                APP_TIMER_MODE_REPEATED,
                                battery_level_meas_timeout_handler);
    APP_ERROR_CHECK(err_code);

    err_code = app_timer_create(&m_heart_rate_timer_id,
                                APP_TIMER_MODE_REPEATED,
                                heart_rate_meas_timeout_handler);
    APP_ERROR_CHECK(err_code);
}

使用app_timer_create创建了两个时钟，处理函数分别是battery_level_meas_timeout_handler和heart_rate_meas_timeout_handler。

/**@brief Function for handling the Battery measurement timer timeout.
 *
 * @details This function will be called each time the battery level measurement timer expires.
 *          This function will start the ADC.
 *
 * @param[in]   p_context   Pointer used for passing some arbitrary information (context) from the
 *                          app_start_timer() call to the timeout handler.
 */
static void battery_level_meas_timeout_handler(void * p_context)
{
    UNUSED_PARAMETER(p_context);
    battery_start();
}


/**@brief Function for handling the Heart rate measurement timer timeout.
 *
 * @details This function will be called each time the heart rate measurement timer expires.
 *          It will exclude RR Interval data from every third measurement.
 *
 * @param[in]   p_context   Pointer used for passing some arbitrary information (context) from the
 *                          app_start_timer() call to the timeout handler.
 */
static void heart_rate_meas_timeout_handler(void * p_context)
{
    uint32_t err_code;

    UNUSED_PARAMETER(p_context);

    err_code = ble_hrs_heart_rate_measurement_send(&m_hrs, m_cur_heart_rate);

    if (
        (err_code != NRF_SUCCESS)
        &&
        (err_code != NRF_ERROR_INVALID_STATE)
        &&
        (err_code != BLE_ERROR_NO_TX_BUFFERS)
        &&
        (err_code != BLE_ERROR_GATTS_SYS_ATTR_MISSING)
    )
    {
        APP_ERROR_HANDLER(err_code);
    }
}

时钟创建后并不会自动运行，当调用application_timers_start后时钟开始运行：

/**@brief Function for starting the application timers.
 */
static void application_timers_start(void)
{
    uint32_t err_code;

    // Start application timers
    err_code = app_timer_start(m_battery_timer_id, BATTERY_LEVEL_MEAS_INTERVAL, NULL);
    APP_ERROR_CHECK(err_code);

    err_code = app_timer_start(m_heart_rate_timer_id, HEART_RATE_MEAS_INTERVAL, NULL);
    APP_ERROR_CHECK(err_code);
}

services_init()初始化程序中的三个服务：ble_dis.c, ble_bas.c, ble_hrs.c。

/**@brief Function for initializing the services that will be used by the application.
 *
 * @details Initialize the Heart Rate, Battery and Device Information services.
 */
static void services_init(void)
{
    uint32_t       err_code;
    ble_hrs_init_t hrs_init;
    ble_bas_init_t bas_init;
    ble_dis_init_t dis_init;
    uint8_t        body_sensor_location;

    // Initialize Heart Rate Service
    body_sensor_location = BLE_HRS_BODY_SENSOR_LOCATION_FINGER;

    memset(&hrs_init, 0, sizeof(hrs_init));
    
    hrs_init.is_sensor_contact_supported = false;
    hrs_init.p_body_sensor_location      = &body_sensor_location;

    // Here the sec level for the Heart Rate Service can be changed/increased.
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&hrs_init.hrs_hrm_attr_md.cccd_write_perm);
    BLE_GAP_CONN_SEC_MODE_SET_NO_ACCESS(&hrs_init.hrs_hrm_attr_md.read_perm);
    BLE_GAP_CONN_SEC_MODE_SET_NO_ACCESS(&hrs_init.hrs_hrm_attr_md.write_perm);

    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&hrs_init.hrs_bsl_attr_md.read_perm);
    BLE_GAP_CONN_SEC_MODE_SET_NO_ACCESS(&hrs_init.hrs_bsl_attr_md.write_perm);

    err_code = ble_hrs_init(&m_hrs, &hrs_init);
    APP_ERROR_CHECK(err_code);

    // Initialize Battery Service
    memset(&bas_init, 0, sizeof(bas_init));

    // Here the sec level for the Battery Service can be changed/increased.
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&bas_init.battery_level_char_attr_md.cccd_write_perm);
    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&bas_init.battery_level_char_attr_md.read_perm);
    BLE_GAP_CONN_SEC_MODE_SET_NO_ACCESS(&bas_init.battery_level_char_attr_md.write_perm);

    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&bas_init.battery_level_report_read_perm);

    bas_init.evt_handler          = NULL;
    bas_init.support_notification = true;
    bas_init.p_report_ref         = NULL;
    bas_init.initial_batt_level   = 100;

    err_code = ble_bas_init(&bas, &bas_init);
    APP_ERROR_CHECK(err_code);

    // Initialize Device Information Service
    memset(&dis_init, 0, sizeof(dis_init));

    ble_srv_ascii_to_utf8(&dis_init.manufact_name_str, MANUFACTURER_NAME);

    BLE_GAP_CONN_SEC_MODE_SET_OPEN(&dis_init.dis_attr_md.read_perm);
    BLE_GAP_CONN_SEC_MODE_SET_NO_ACCESS(&dis_init.dis_attr_md.write_perm);

    err_code = ble_dis_init(&dis_init);
    APP_ERROR_CHECK(err_code);
}

static ble_hrs_t的结构定义：

/**@brief Heart Rate Service structure. This contains various status information for the service. */
typedef struct ble_hrs_s
{
    ble_hrs_evt_handler_t        evt_handler;                                          /**< Event handler to be called for handling events in the Heart Rate Service. */
    bool                         is_expended_energy_supported;                         /**< TRUE if Expended Energy measurement is supported. */
    bool                         is_sensor_contact_supported;                          /**< TRUE if sensor contact detection is supported. */
    uint16_t                     service_handle;                                       /**< Handle of Heart Rate Service (as provided by the BLE stack). */
    ble_gatts_char_handles_t     hrm_handles;                                          /**< Handles related to the Heart Rate Measurement characteristic. */
    ble_gatts_char_handles_t     bsl_handles;                                          /**< Handles related to the Body Sensor Location characteristic. */
    ble_gatts_char_handles_t     hrcp_handles;                                         /**< Handles related to the Heart Rate Control Point characteristic. */
    uint16_t                     conn_handle;                                          /**< Handle of the current connection (as provided by the BLE stack, is BLE_CONN_HANDLE_INVALID if not in a connection). */
    bool                         is_sensor_contact_detected;                           /**< TRUE if sensor contact has been detected. */
    uint16_t                     rr_interval[BLE_HRS_MAX_BUFFERED_RR_INTERVALS];       /**< Set of RR Interval measurements since the last Heart Rate Measurement transmission. */
    uint16_t                     rr_interval_count;                                    /**< Number of RR Interval measurements since the last Heart Rate Measurement transmission. */
} ble_hrs_t;

ble_hrs.h/ble_hrs.c是心率计程序服务的代码。

buttons_init(void)初始化两个按钮：HR_INC_BUTTON_PIN_NO和HR_DEC_BUTTON_PIN_NO，分别模拟心率计的加减。

/**@brief Function for initializing the button module.
 */
static void buttons_init(void)
{
    // Configure HR_INC_BUTTON_PIN_NO and HR_DEC_BUTTON_PIN_NO as wake up buttons and also configure
    // for 'pull up' because the eval board does not have external pull up resistors connected to
    // the buttons.
    static app_button_cfg_t buttons[] =
    {
        {HR_INC_BUTTON_PIN_NO, false, BUTTON_PULL, button_event_handler},
        {HR_DEC_BUTTON_PIN_NO, false, BUTTON_PULL, button_event_handler}  // Note: This pin is also BONDMNGR_DELETE_BUTTON_PIN_NO
    };
    
    APP_BUTTON_INIT(buttons, sizeof(buttons) / sizeof(buttons[0]), BUTTON_DETECTION_DELAY, false);
}

当按下按钮时，处理程序是button_event_handler()，它处理心率计的加减模拟：

/**@brief Function for handling button events.
 *
 * @param[in]   pin_no   The pin number of the button pressed.
 */
static void button_event_handler(uint8_t pin_no, uint8_t button_action)
{
    if (button_action == APP_BUTTON_PUSH)
    {
        switch (pin_no)
        {
            case HR_INC_BUTTON_PIN_NO:
                // Increase Heart Rate measurement
                m_cur_heart_rate += HEART_RATE_CHANGE;
                if (m_cur_heart_rate > MAX_HEART_RATE)
                {
                    m_cur_heart_rate = MIN_HEART_RATE; // Loop back
                }
                break;
                
            case HR_DEC_BUTTON_PIN_NO:
                // Decrease Heart Rate measurement
                m_cur_heart_rate -= HEART_RATE_CHANGE;
                if (m_cur_heart_rate < MIN_HEART_RATE)
                {
                    m_cur_heart_rate = MAX_HEART_RATE; // Loop back
                }
                break;
                
            default:
                APP_ERROR_HANDLER(pin_no);
                break;
        }
    }    
}