FRDM-MCXN947 sysTick basic

saulius1005 — Thu, 28 Mar 2024 10:15:01 GMT

Today I start to play with sysTick() Timer and trying to make simple code to generate simple output signal

simplest code possible:

and problem is no matter how much I changing clock frequency value (12Mhz or 150Mhz)output signal is all time the same (interrupt period) ~827kHz.

clock selection from default values at config tools:

what i am doing wrong?

Re: FRDM-MCXN947 sysTick basic

xiangjun_rong — Fri, 29 Mar 2024 02:30:37 GMT

Hi,

As you know that the systick module interrupt period is dependent on the driving clock and SysTick Reload Value Register, which functions as a divider

systick period=driving_clock/Reload_Value

Peripheral Configuration tools can adjust the Reload_Value in SysTick Reload Value Register based on the driving clock so that it can get the constant period you has defined.

I suppose that you can call the function directly which set the SysTick Reload Value Register and enable the systick:

__STATIC_INLINE uint32_t SysTick_Config(uint32_t ticks)
{
if ((ticks - 1UL) > SysTick_LOAD_RELOAD_Msk)
 {
return (1UL); /* Reload value impossible */
 }
 
 SysTick->LOAD = (uint32_t)(ticks - 1UL); /* set reload register */
 NVIC_SetPriority (SysTick_IRQn, (1UL << __NVIC_PRIO_BITS) - 1UL); /* set Priority for Systick Interrupt */
 SysTick->VAL = 0UL; /* 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 (0UL); /* Function successful */
}
This is systick module clock source:
 
Hope it can help you
BR
XiangJun Rong

topic Re: FRDM-MCXN947 sysTick basic in MCX Microcontrollers

FRDM-MCXN947 sysTick basic

Re: FRDM-MCXN947 sysTick basic