stm32 study notes systick timer

Systick was originally designed to provide a ticking clock for the convenience of porting operating systems.

I came into contact with STM32 again a few days ago and used the V3.5 library. Suddenly I found that the cumbersome Systick usage was simplified into one sentence.

Right now:

 void SysTick_Configuration(void)
{
  if (SysTick_Config(SystemCoreClock / 1000000))//72, 1us per tick
  {
    /* Capture error */
    while (1);
  }
}

The Systick_Config function has replaced all previous setup processes.

The systick.c file was also deleted, and the function was directly included in the kernel file core_cm3.h.

/* ##################################    SysTick function  ############################################ */

#if (!defined (__Vendor_SysTickConfig)) || (__Vendor_SysTickConfig == 0)

/**
 * @brief  Initialize and start the SysTick counter and its interrupt.
 *
 * @param   ticks   number of ticks between two interrupts
 * @return  1 = failed, 0 = successful
 *
 * Initialise the system tick timer and its interrupt and start the
 * system tick timer / counter in free running mode to generate 
 * periodical interrupts.
 */
static __INLINE uint32_t SysTick_Config(uint32_t ticks)
{ 
  if (ticks > SysTick_LOAD_RELOAD_Msk)  return (1);            /* Reload value impossible */
                                                               
  SysTick->LOAD  = (ticks & SysTick_LOAD_RELOAD_Msk) - 1;      /* set reload register */
  NVIC_SetPriority (SysTick_IRQn, (1<<__NVIC_PRIO_BITS) - 1);  /* set Priority for Cortex-M0 System Interrupts */
  SysTick->VAL   = 0;                                          /* Load the SysTick Counter Value */
  SysTick->CTRL  = SysTick_CTRL_CLKSOURCE_Msk | 
                   SysTick_CTRL_TICKINT_Msk   | 
                   SysTick_CTRL_ENABLE_Msk;                    /* Enable SysTick IRQ and SysTick Timer */
  return (0);                                                  /* Function successful */
}

#endif

The advantage is that the setup is quite simple.

The downside is that the control is not as flexible as before, and once enabled, there is really no library function to easily overload or disable it.