RTC — 内部低频时钟校准

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#include "at32f403a_407_board.h"
#include "at32f403a_407_clock.h"

int main(void)
{
  tmr_input_config_type tmr_ic_init_structure;

  system_clock_config();

  at32_board_init();

  uart_print_init(115200);

  /* rtc configuration */
  rtc_configuration();

  printf("\r\n\nstart calib\r\n\r\n");

  /* get the frequency value */
  crm_clocks_freq_get(&crm_clocks);

  /* enable tmr5 apb1 clocks */
  crm_periph_clock_enable(CRM_TMR5_PERIPH_CLOCK, TRUE);
  crm_periph_clock_enable(CRM_IOMUX_PERIPH_CLOCK, TRUE);

  /* connect internally the tm5_ch4 input capture to the lick clock output */
  gpio_pin_remap_config(TMR5CH4_MUX, TRUE);

  /* tmr5 time base configuration */
  tmr_base_init(TMR5, 0xFFFF, 0);
  tmr_cnt_dir_set(TMR5, TMR_COUNT_UP);
  tmr_clock_source_div_set(TMR5, TMR_CLOCK_DIV1);

  /* tmr5 channel4 input capture mode configuration */
  tmr_input_default_para_init(&tmr_ic_init_structure);
  tmr_ic_init_structure.input_channel_select = TMR_SELECT_CHANNEL_4;
  tmr_ic_init_structure.input_polarity_select = TMR_INPUT_RISING_EDGE;
  tmr_ic_init_structure.input_mapped_select = TMR_CC_CHANNEL_MAPPED_DIRECT;
  tmr_ic_init_structure.input_filter_value = 0;
  tmr_input_channel_init(TMR5, &tmr_ic_init_structure, TMR_CHANNEL_INPUT_DIV_1);

  /* reinitialize the index for the interrupt */
  operationcomplete = 0;

  /* enable the tmr5 input capture counter */
  tmr_counter_enable(TMR5, TRUE);

  /* Reset all tmr5 flags */
  tmr_flag_get(TMR5, TMR_C4_FLAG);

  /* enable the tmr5 channel 4 */
  tmr_interrupt_enable(TMR5, TMR_C4_INT, TRUE);

  /* nvic configuration */
  nvic_configuration();

  /* wait the tmr5 measuring operation to be completed */
  while(operationcomplete != 2);

  /* compute the actual frequency of the lick. (tim5_clk = 1 * pclk1)  */
  if(periodvalue != 0)
  {
    lickfreq = (uint32_t)((uint32_t)(crm_clocks.apb1_freq * 2) / (uint32_t)periodvalue);
  }

  printf("apb1_freq    = %d\r\n", crm_clocks.apb1_freq);
  printf("period_value = %d\r\n", periodvalue);
  printf("lick_freq    = %d\r\n", lickfreq);

  /* adjust the rtc prescaler value */
  rtc_divider_set((lickfreq - 1));

  /* wait for the register write to complete */
  rtc_wait_config_finish();

  /* turn on led2 */
  at32_led_on(LED2);

  while(1)
  {
  }
}