NRF51822之32Mhz

#if defined( USB_SYSTEM_CLOCK_32MHZ)
#define DEVICE_NAME                     "Nordic_UART_32mhz"                               /**< Name of device. Will be included in the advertising data. */
#else
#define DEVICE_NAME                     "Nordic_UART"                               /**< Name of device. Will be included in the advertising data. */
#endif//USB_SYSTEM_CLOCK_32MHZ

#if defined (USB_SYSTEM_CLOCK_32MHZ)
/**@brief Function for Set the external high frequency clock source to 32 MHz .
 */
static void setClock( void )
{
    // Set the external high frequency clock source to 32 MHz
    NRF_CLOCK->XTALFREQ = 0xFFFFFF00;
    
    // Start the external high frequency crystal
    NRF_CLOCK->EVENTS_HFCLKSTARTED = 0;
    NRF_CLOCK->TASKS_HFCLKSTART = 1;
    
    // Wait for the external oscillator to start up
    while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0) {}
    
}
#endif//USB_SYSTEM_CLOCK_32MHZ

/**@brief Application main function.
 */
int main(void)
{
    uint32_t err_code;
    bool erase_bonds;
    uint8_t  start_string[] = START_STRING;

  #if defined (USB_SYSTEM_CLOCK_32MHZ)   
    setClock();
  #endif//USB_SYSTEM_CLOCK_32MHZ  


    // Initialize.
    APP_TIMER_INIT(APP_TIMER_PRESCALER, APP_TIMER_OP_QUEUE_SIZE, false);
    uart_init();
    buttons_leds_init(&erase_bonds);
    ble_stack_init();
    gap_params_init();
    services_init();
    advertising_init();
    conn_params_init();
    
    printf("%s",start_string);

    err_code = ble_advertising_start(BLE_ADV_MODE_FAST);
    APP_ERROR_CHECK(err_code);
    
    // Enter main loop.
    for (;;)
    {
        power_manage();
    }
}

#if defined( USB_SYSTEM_CLOCK_32MHZ)
#define __SYSTEM_CLOCK      (32000000UL)     /*!< nRF51 devices use a fixed System Clock Frequency of 32MHz */
#else
#define __SYSTEM_CLOCK      (16000000UL)     /*!< nRF51 devices use a fixed System Clock Frequency of 16MHz */
#endif//USB_SYSTEM_CLOCK_32MHZ