问HAL_GetTick()是返回滴答还是毫秒？(以及如何测量微秒)

EN

/**
  * @brief This function provides minimum delay (in milliseconds) based
  *        on variable incremented.
  * @note In the default implementation , SysTick timer is the source of time base.
  *       It is used to generate interrupts at regular time intervals where uwTick
  *       is incremented.
  * @note This function is declared as __weak to be overwritten in case of other
  *       implementations in user file.
  * @param Delay specifies the delay time length, in milliseconds.
  * @retval None
  */
__weak void HAL_Delay(uint32_t Delay)
{
  uint32_t tickstart = HAL_GetTick();
  uint32_t wait = Delay;

  /* Add a period to guaranty minimum wait */
  if (wait < HAL_MAX_DELAY)
  {
    wait++;
  }

  while((HAL_GetTick() - tickstart) < wait)
  {
  }
}

uint32_t getCurrentMicros(void)
{
  /* Ensure COUNTFLAG is reset by reading SysTick control and status register */
  LL_SYSTICK_IsActiveCounterFlag();
  uint32_t m = HAL_GetTick();
  const uint32_t tms = SysTick->LOAD + 1;
  __IO uint32_t u = tms - SysTick->VAL;
  if (LL_SYSTICK_IsActiveCounterFlag()) {
    m = HAL_GetTick();
    u = tms - SysTick->VAL;
  }
  return (m * 1000 + (u * 1000) / tms);
}

static inline uint32_t LL_SYSTICK_IsActiveCounterFlag(void)
{
  return ((SysTick->CTRL & SysTick_CTRL_COUNTFLAG_Msk) == (SysTick_CTRL_COUNTFLAG_Msk));
}