1、找到头文件 FreeRTOSConfig.h 有如下定义。
#define configCPU_CLOCK_HZ ((unsigned long)168000000) //CPU频率
#define configTICK_RATE_HZ (( portTickType )1000) //时钟节拍频率，这里设置为1000，周期就是1ms
2、搜索 configTICK_RATE_HZ，在port.c中。
portNVIC_SYSTICK_LOAD_REG = ( configSYSTICK_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;
portNVIC_SYSTICK_CTRL_REG = ( portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT );
3、搜索 portNVIC_SYSTICK_CTRL_REG，在port.c中。
#define portNVIC_SYSTICK_CTRL_REG ( * ( ( volatile uint32_t * ) 0xe000e010 ) )
#define portNVIC_SYSTICK_LOAD_REG ( * ( ( volatile uint32_t * ) 0xe000e014 ) )
4、下面证明地址是不是SYSTICK的配置地址。
STM32库函数中core_cm4.h中配置systick函数为 uint32_t SysTick_Config(uint32_t ticks)
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 */
5、跳转到 SysTick 定义处。
#define SCS_BASE (0xE000E000UL) /*!< System Control Space Base Address */
#define ITM_BASE (0xE0000000UL) /*!< ITM Base Address */
#define DWT_BASE (0xE0001000UL) /*!< DWT Base Address */
#define TPI_BASE (0xE0040000UL) /*!< TPI Base Address */
#define CoreDebug_BASE (0xE000EDF0UL) /*!< Core Debug Base Address */
#define SysTick_BASE (SCS_BASE + 0x0010UL) /*!< SysTick Base Address */
#define NVIC_BASE (SCS_BASE + 0x0100UL) /*!< NVIC Base Address */
#define SCB_BASE (SCS_BASE + 0x0D00UL) /*!< System Control Block Base Address */
#define SCnSCB ((SCnSCB_Type *) SCS_BASE ) /*!< System control Register not in SCB */
#define SCB ((SCB_Type *) SCB_BASE ) /*!< SCB configuration struct */
#define SysTick ((SysTick_Type *) SysTick_BASE ) /*!< SysTick configuration struct */