STM32 Quick Learning 6——SysTick Timing 1s Control LED

Setting Pin Function

Set systick to 1s interrupt

Using systick interruption, you can get 1s time

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The systick of stm32 is set by a few programs. After using the systick_config() function, its loaded value is your parameter, and the interrupt is automatically turned on, and the interrupt is set to the lowest priority, and its clock is set to HCLK, that is, the system clock 72mhz, and the count register is reset to start counting. The clock can also be set to eight times the frequency of HCKL by using SysTick_CLKSourceConfig(SysTick_CLKSource_HCLK_Div8) immediately following systick_config(), and changing the priority uses the NVIC_SetPriority(SysTick_IRQn,...) function, and the time base unit is set using the following formula, Reload Value = SysTick Counter Clock (Hz) x Desired Time base (s) Reload Value is the parameter passed in. But the parameter cannot exceed 0xFFFFFF.
Systick's clock includes internal clock and external clock. For stm32, its internal clock FCLK is the AHB clock, 72MHz, and the external clock STCLK is the clock after 8 division, 9MHz. Therefore, when using the systick_config() function, its default clock is 72MHz.

When using systick delay, you can also read and write its registers directly without enabling interrupts.

SysTick_Config(uint32_t  ticks): Set the system tick clock and enable interrupts

         The description of the STM32 core is different from that of the CM3 core. There are two clock sources: AHB/8 and AHB. In this function, HCLK is selected.

(SysTick_CTRL_CLKSOURCE_Msk), so the timing time = ticks  /  HCLK. When the timing is 10ms and the HCLK is 24MHz, ticks  =  10000  *  24  =  240000.

         If you need to select HCLK/8, you can modify this function directly, or follow this function with SysTick_CLKSourceConfig(uint32_t SysTick_CLKSource) in misc  to set it

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The 3.4 library is used here, note that it is SystemCoreClock, the 3.0 versions use the word SystemFrequency, the methods of other 2.x versions are different.

Note: The global variable TimingDelay must be defined as volatile type, and the delay time will not change with the system clock frequency.

Main file

#include "stm32f10x.h"

void RCC_Configuration(void);

void GPIO_Configuration(void);

void SysTick_Configuration(void);

void Delay(volatile uint32_t nTime);

static volatile uint32_t TimingDelay;

int main(void)

{

  RCC_Configuration();

  GPIO_Configuration();

  SysTick_Configuration();

  while(1)

  {

    GPIO_SetBits(GPIOA, GPIO_Pin_0); 

    Delay(1000);

    GPIO_SetBits(GPIOA, GPIO_Pin_1);

    Delay(1000);

    GPIO_ResetBits(GPIOA, GPIO_Pin_0);

Delay(1000);

    GPIO_ResetBits(GPIOA, GPIO_Pin_1);

Delay(1000);

  }

}

void RCC_Configuration(void) /*Use external 8M*/

{    

  ErrorStatus HSEStartUpStatus;

  /* RCC system reset(for debug purpose) */

  RCC_DeInit();

  /* Enable HSE */

  RCC_HSEConfig(RCC_HSE_ON);

  /* Wait till HSE is ready */

  HSEStartUpStatus = RCC_WaitForHSEStartUp();

  if(HSESTartUpStatus == SUCCESS)

  {

    /* Enable Prefetch Buffer Prefetch buffer enable */

    FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);

    /* Flash 2 wait state, FLASH memory delay clock cycles*/

    FLASH_SetLatency(FLASH_Latency_2);

    /* HCLK = SYSCLK */

    RCC_HCLKConfig(RCC_SYSCLK_Div1); 

    /* PCLK2 = HCLK */

    RCC_PCLK2Config(RCC_HCLK_Div1); 

    /* PCLK1 = HCLK/2 */

    RCC_PCLK1Config(RCC_HCLK_Div2);

    /* PLLCLK = 8MHz * 9 = 72 MHz */

    RCC_PLLConfig(RCC_PLLSource_HSE_Div1, RCC_PLLMul_9);

    /* Enable PLL */ 

    RCC_PLLCmd(ENABLE);

    /* Wait till PLL is ready */

    while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET)

    {

    }

    /* Select PLL as system clock source */

    RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);

    /* Wait till PLL is used as system clock source */

    while(RCC_GetSYSCLKSource() != 0x08)

    {

    }

  }

  /* Enable GPIOC clock */

  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);

}

void GPIO_Configuration(void)

{

  GPIO_InitTypeDef GPIO_InitStructure;

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_1;

  GPIO_InitStructure.GPIO_Speed ​​= GPIO_Speed_50MHz;

  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;

  GPIO_Init(GPIOA, &GPIO_InitStructure);

}

void SysTick_Configuration()

{

  if (SysTick_Config(SystemCoreClock / 1000))

  { 

    /* Capture error */ 

    while (1);

  }

}

void Delay(volatile uint32_t nTime)

{ 

  TimingDelay = nTime;

  while(TimingDelay != 0);

}

void TimingDelay_Decrement(void)

{

  if (TimingDelay != 0x00)

  { 

    TimingDelay--;

  }

}

Stm32f10x_it.c added

void TimingDelay_Decrement(void);

void SysTick_Handler(void)

{

  TimingDelay_Decrement();

}