STM32 system timer flashing LED

SysTick Register introduction

SysTick Register summary

Register name	Register description
CTRL	SysTick Control and status register
LOAD	SysTick Reload the load value register
VAL	SysTick Current value register
CALIB	SysTick Calibration value register

①SysTick Control and status register

Bit segment	name	type	reset value	describe
16	COUNTFLAG	R/W	0	If after last reading this register ,SysTick It has been counted 0, The bit is 1
2	CLKSOURCE	R/W	0	Clock source selection bit ,0=AHB/8,1= Processor clock AHB
1	TICKINT	R/W	0	1：SysTick Count down to 0 Time production SysTick Exception request ,0： Count to 0 No action
0	ENABLE	R/W	0	SysTick Enable bit of timer

②SystTick Reload the load value register

Bit segment	name	type	reset value	describe
23：0	RELOAD	R/W	0	When count down to 0 when , Values to be reloaded

③SysTick Current value register

Bit segment	name	type	reset value	describe
23：0	CURRENT	R/W	0	When reading, return the value of the current reciprocal count , Writing it clears it , At the same time, it will also clean up in SysTick Control and status register COUNTFLAG sign

SysTick Timing experiments

Programming points

1） Set the value of the reload register .
2） Clear the value of the current value register .
3） Configure control and status registers .

bsp_led.c file

#include "./led/bsp_led.h" 

void LED_GPIO_Config(void)
{
    		
		
		GPIO_InitTypeDef GPIO_InitStructure;
		RCC_APB2PeriphClockCmd( LED1_GPIO_CLK | LED2_GPIO_CLK | LED3_GPIO_CLK, ENABLE);
		GPIO_InitStructure.GPIO_Pin = LED1_GPIO_PIN;	
		GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;   
		GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; 
		GPIO_Init(LED1_GPIO_PORT, &GPIO_InitStructure);	
		GPIO_InitStructure.GPIO_Pin = LED2_GPIO_PIN;
		GPIO_Init(LED2_GPIO_PORT, &GPIO_InitStructure);
		GPIO_InitStructure.GPIO_Pin = LED3_GPIO_PIN;
		GPIO_Init(LED3_GPIO_PORT, &GPIO_InitStructure);
		GPIO_SetBits(LED1_GPIO_PORT, LED1_GPIO_PIN);
		GPIO_SetBits(LED2_GPIO_PORT, LED2_GPIO_PIN);	 
		GPIO_SetBits(LED3_GPIO_PORT, LED3_GPIO_PIN);
}

bsp_led.h file

#ifndef __LED_H
#define __LED_H

#include "stm32f10x.h"

#define LED1_GPIO_PORT GPIOB 
#define LED1_GPIO_CLK RCC_APB2Periph_GPIOB 
#define LED1_GPIO_PIN GPIO_Pin_5 

#define LED2_GPIO_PORT GPIOB 
#define LED2_GPIO_CLK RCC_APB2Periph_GPIOB 
#define LED2_GPIO_PIN GPIO_Pin_0 

#define LED3_GPIO_PORT GPIOB 
#define LED3_GPIO_CLK RCC_APB2Periph_GPIOB 
#define LED3_GPIO_PIN GPIO_Pin_1 

#define ON 0
#define OFF 1

#define LED1(a) if (a) \ GPIO_SetBits(LED1_GPIO_PORT,LED1_GPIO_PIN);\ else \ GPIO_ResetBits(LED1_GPIO_PORT,LED1_GPIO_PIN)

#define LED2(a) if (a) \ GPIO_SetBits(LED2_GPIO_PORT,LED2_GPIO_PIN);\ else \ GPIO_ResetBits(LED2_GPIO_PORT,LED2_GPIO_PIN)

#define LED3(a) if (a) \ GPIO_SetBits(LED3_GPIO_PORT,LED3_GPIO_PIN);\ else \ GPIO_ResetBits(LED3_GPIO_PORT,LED3_GPIO_PIN)

#define digitalHi(p,i) {
      p->BSRR=i;} 
#define digitalLo(p,i) {
      p->BRR=i;} 

#define LED1_TOGGLE digitalToggle(LED1_GPIO_PORT,LED1_GPIO_PIN)
#define LED1_OFF digitalHi(LED1_GPIO_PORT,LED1_GPIO_PIN)
#define LED1_ON digitalLo(LED1_GPIO_PORT,LED1_GPIO_PIN)

#define LED2_TOGGLE digitalToggle(LED2_GPIO_PORT,LED2_GPIO_PIN)
#define LED2_OFF digitalHi(LED2_GPIO_PORT,LED2_GPIO_PIN)
#define LED2_ON digitalLo(LED2_GPIO_PORT,LED2_GPIO_PIN)

#define LED3_TOGGLE digitalToggle(LED3_GPIO_PORT,LED3_GPIO_PIN)
#define LED3_OFF digitalHi(LED3_GPIO_PORT,LED3_GPIO_PIN)
#define LED3_ON digitalLo(LED3_GPIO_PORT,LED3_GPIO_PIN)

void LED_GPIO_Config(void);

#endif /* __LED_H */

bsp_SysTick.h file

#ifndef __SYSTICK_H
#define __SYSTICK_H

#include "stm32f10x.h"

void SysTick_Init(void);
void Delay_us(__IO u32 nTime);
#define Delay_ms(x) Delay_us(100*x) // Company ms

void SysTick_Delay_Us( __IO uint32_t us);
void SysTick_Delay_Ms( __IO uint32_t ms);


#endif /* __SYSTICK_H */

bsp_SysTick.c file

#include "bsp_SysTick.h"
#include "core_cm3.h"
#include "misc.h"

static __IO u32 TimingDelay;
 
/*  Start the system tick timer  */
void SysTick_Init(void)
{
    
	/* SystemCoreClock / 1000 1ms Break once  * SystemCoreClock / 100000 10us Break once  * SystemCoreClock / 1000000 1us Break once  */
	if (SysTick_Config(SystemCoreClock / 100000))
	{
     
		/* Capture error */ 
		while (1);
	}
}

/* Delay_us(1)： Realization 1x10us = 10us Time delay  */
void Delay_us(__IO u32 nTime)
{
     
	TimingDelay = nTime;	

	// Enable tick timer 
	SysTick->CTRL |=  SysTick_CTRL_ENABLE_Msk;

	while(TimingDelay != 0);
}

// Get the beat program , stay SysTick Interrupt function SysTick_Handler() Call in 
void TimingDelay_Decrement(void)
{
    
	if (TimingDelay != 0x00)
	{
     
		TimingDelay--;
	}
}

#if 0
//  This firmware library function is in core_cm3.h in 
static __INLINE uint32_t SysTick_Config(uint32_t ticks)
{
     
  // reload  The register is 24bit, The maximum value is 2^24
	if (ticks > SysTick_LOAD_RELOAD_Msk)  return (1);
  
  //  To configure reload Initial value  
  SysTick->LOAD  = (ticks & SysTick_LOAD_RELOAD_Msk) - 1;
	
  // Configure interrupt priority as ：1<<4-1 = 15, The priority is the lowest 
  NVIC_SetPriority (SysTick_IRQn, (1<<__NVIC_PRIO_BITS) - 1); 
	
  // To configure counter The value of the counter 
  SysTick->VAL   = 0;
	
	// To configure systick The clock is 72M
	// Interrupt enable 
	// Can make systick
  SysTick->CTRL  = SysTick_CTRL_CLKSOURCE_Msk|SysTick_CTRL_TICKINT_Msk|SysTick_CTRL_ENABLE_Msk;                    
  return (0); 
}
#endif

// couter Minus one is equal to 1/systick_clk
// When counter  from reload  The value of is reduced to 0 When , For a cycle , If interrupt is turned on, the interrupt service program is executed .
// meanwhile CTRL Of countflag Position meeting position 1
// The time of this cycle is ：reload * (1/systick_clk)

void SysTick_Delay_Us( __IO uint32_t us)//SysTick Subtle level delay 
{
    
	uint32_t i;
	SysTick_Config(SystemCoreClock/1000000);
	
	for(i=0;i<us;i++)
	{
    
		// When the value of the counter is reduced to 0 When ,CRTL Bit of register 16 I'll set 1
		while( !((SysTick->CTRL)&(1<<16)) );
	}
	// close SysTick Timer 
	SysTick->CTRL &=~SysTick_CTRL_ENABLE_Msk;
}

void SysTick_Delay_Ms( __IO uint32_t ms)//SysTick Millisecond delay 
{
    
	uint32_t i;	
	SysTick_Config(SystemCoreClock/1000);
	
	for(i=0;i<ms;i++)
	{
    
		// When the value of the counter is reduced to 0 When ,CRTL Bit of register 16 I'll set 1
		// Dangzhi 1 when , Reading this bit clears 0
		while( !((SysTick->CTRL)&(1<<16)) );
	}
	// close SysTick Timer 
	SysTick->CTRL &=~ SysTick_CTRL_ENABLE_Msk;
}

main.c file

#include "stm32f10x.h"
#include "bsp_SysTick.h"
#include "bsp_led.h"

int main(void)
{
    	
	/* LED Port initialization  */
	LED_GPIO_Config();

	/*  To configure SysTick  by 10us Break once */
	SysTick_Init();
#if 0 
	for(;;)
	{
    

		LED1( ON ); 
	    Delay_us(100000);    	// 100000 * 10us = 1000ms
		//Delay_ms(100);
		LED1( OFF );
	  
		LED2( ON );
	    Delay_us(100000);		// 100000 * 10us = 1000ms
		//Delay_ms(100);
		LED2( OFF );
	
		LED3( ON );
	    Delay_us(100000);		// 100000 * 10us = 1000ms
		//Delay_ms(100);
		LED3( OFF );
	}     
#else
	for(;;)
	{
    

		LED1( ON ); 
		SysTick_Delay_Ms( 1000 );
		LED1( OFF );
	  
		LED2( ON );
		SysTick_Delay_Ms( 1000 );
		LED2( OFF );
	
		LED3( ON );
		SysTick_Delay_Ms( 1000 );
		LED3( OFF );
	} 
#endif 
}

Running results