nrf51822自学笔记（三）心率计

依旧是官方给的例程恩……

int main(void)
{

uint32_t err_code;

timers_init();
gpiote_init();
buttons_init();
ble_stack_init();
device_manager_init();

// Initialize Bluetooth Stack parameters.
gap_params_init();//初始化gap层连接
advertising_init();
services_init();
conn_params_init();

// Start advertising.
advertising_start();//启动定时器，battery每2S发送一次数据，heart rate每1S发送一次数据

// 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);
}
}

先初始化，初始化了定时器，GPIO TASK&EVENT，按钮（pin16和pin17）BLE stack，device manager，gap层连接，广播，services，和conn params(相关参数）

为啥battery每2s发送一次数据，heart rate每1s发送一次数据-。-在后面有解释

来看看初始化BLE stack的函数

static void ble_stack_init(void)
{
uint32_t err_code;

// Initialize the SoftDevice handler module.
SOFTDEVICE_HANDLER_INIT(NRF_CLOCK_LFCLKSRC_XTAL_20_PPM, false);

// Enable BLE stack
ble_enable_params_t ble_enable_params;
memset(&ble_enable_params, 0, sizeof(ble_enable_params));
ble_enable_params.gatts_enable_params.service_changed = IS_SRVC_CHANGED_CHARACT_PRESENT;
err_code = sd_ble_enable(&ble_enable_params);
APP_ERROR_CHECK(err_code);

// Register with the SoftDevice handler module for BLE events.
err_code = softdevice_ble_evt_handler_set(ble_evt_dispatch);//若event发生，进入ble_evt_dispatch
APP_ERROR_CHECK(err_code);

// Register with the SoftDevice handler module for BLE system events.
err_code = softdevice_sys_evt_handler_set(sys_evt_dispatch);//若system event，进入sys_evt_dispatch
APP_ERROR_CHECK(err_code);
}

若event发生，则进入ble_evt_dispatch()，追踪一下

static void ble_evt_dispatch(ble_evt_t * p_ble_evt)
{
dm_ble_evt_handler(p_ble_evt);//事件处理函数
ble_hrs_on_ble_evt(&m_hrs, p_ble_evt);//hrs service event处理函数
ble_bas_on_ble_evt(&bas, p_ble_evt);//bas service event处理函数
ble_conn_params_on_ble_evt(p_ble_evt);//连接相关event处理函数
on_ble_evt(p_ble_evt);//自定义函数（亮灯灭灯等）
}

追踪一下on_ble_evt()

static void on_ble_evt(ble_evt_t * p_ble_evt)
{
uint32_t        err_code;

switch (p_ble_evt->header.evt_id)
{
case BLE_GAP_EVT_CONNECTED:
led_stop();

// Initialize the current heart rate to the average of max and min values. So that
// everytime a new connection is made, the heart rate starts from the same value.
m_cur_heart_rate = (MAX_HEART_RATE + MIN_HEART_RATE) / 2;

// Start timers used to generate battery and HR measurements.
application_timers_start();

// Start handling button presses
err_code = app_button_enable();
APP_ERROR_CHECK(err_code);
break;

case BLE_GAP_EVT_DISCONNECTED:
// @note Flash access may not be complete on return of this API. System attributes are now
// stored to flash when they are updated to ensure flash access on disconnect does not
// result in system powering off before data was successfully written.

// Go to system-off mode, should not return from this function, wakeup will trigger
// a reset.
system_off_mode_enter();
break;

case BLE_GAP_EVT_TIMEOUT:
if (p_ble_evt->evt.gap_evt.params.timeout.src == BLE_GAP_TIMEOUT_SRC_ADVERTISEMENT)
{
led_stop();

nrf_gpio_cfg_sense_input(HR_INC_BUTTON_PIN_NO,
BUTTON_PULL,
NRF_GPIO_PIN_SENSE_LOW);

nrf_gpio_cfg_sense_input(HR_DEC_BUTTON_PIN_NO,
BUTTON_PULL,
NRF_GPIO_PIN_SENSE_LOW);

system_off_mode_enter();
}
break;

default:
// No implementation needed.
break;
}
}

1.这个函数用了个switch语句，判断条件的定义可以在ble_gap.h中找到

enum BLE_GAP_EVTS
{
BLE_GAP_EVT_CONNECTED  = BLE_GAP_EVT_BASE,    /**< Connection established. */
BLE_GAP_EVT_DISCONNECTED,                     /**< Disconnected from peer. */
BLE_GAP_EVT_CONN_PARAM_UPDATE,                /**< Connection Parameters updated. */
BLE_GAP_EVT_SEC_PARAMS_REQUEST,               /**< Request to provide security parameters. */
BLE_GAP_EVT_SEC_INFO_REQUEST,                 /**< Request to provide security information. */
BLE_GAP_EVT_PASSKEY_DISPLAY,                  /**< Request to display a passkey to the user. */
BLE_GAP_EVT_AUTH_KEY_REQUEST,                 /**< Request to provide an authentication key. */
BLE_GAP_EVT_AUTH_STATUS,                      /**< Authentication procedure completed with status. */
BLE_GAP_EVT_CONN_SEC_UPDATE,                  /**< Connection security updated. */
BLE_GAP_EVT_TIMEOUT,                          /**< Timeout expired. */
BLE_GAP_EVT_RSSI_CHANGED,                     /**< Signal strength measurement report. */
};

又是一堆枚举常量= =……

2.这个函数设置了心率的一个初始值（毕竟没装传感器，要用某些手段来试一下）

m_cur_heart_rate = (MAX_HEART_RATE + MIN_HEART_RATE) / 2; 追踪一下宏定义发现最小值60最大值300……恩……

3.这个函数调用application_timers_start()，使刚才创建的两个timer运行。

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);
}

0-0这就解释了一下刚才遗留的问题……为什么发送数据battery是2s一次，heart rate是1s一次。追踪一下app_timer_start()中的参数XXX_XXX_MEAS_INTERVAL

#define BATTERY_LEVEL_MEAS_INTERVAL          APP_TIMER_TICKS(2000, APP_TIMER_PRESCALER) /**< Battery level measurement interval (ticks). */

#define HEART_RATE_MEAS_INTERVAL             APP_TIMER_TICKS(1000, APP_TIMER_PRESCALER) /**< Heart rate measurement interval (ticks). */

追踪一下APP_TIMER_TICKS(),追踪到了app_timer.h里

#define APP_TIMER_TICKS(MS, PRESCALER)\
((uint32_t)ROUNDED_DIV((MS) * (uint64_t)APP_TIMER_CLOCK_FREQ, ((PRESCALER) + 1) * 1000))

第一个参数是ms，第二个宏定义 =0 。so0-0问题解决

然后看看初始化按键这个函数

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);
}

注释写的挺清楚……追踪一下button_event_handler()

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://pin16
// 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://pin17
// 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;
}
}
}

一个长且直观的按键扫描，switch判断哪个按键被按下，然后进行当前心率的加减。

通过蓝牙广播1s发送一次数据，在手机端app上显示出来（像一个迟缓的示波器= =）。