[文章]

STM32之SysTick定时中断分析

2014-11-14 18:25:15 5059

0 我们看一看3.5版的库自带模板的main.c里面的说明。 /* Setup Systick Timer for 1 msec interrupts. ------------------------------------------ 1. The SysTick_Config() function is a CMSIS function which configure: - The SysTick Reload register with value passed as function parameter. - Configure the SysTick IRQ priority to the lowest value (0x0F). - Reset the SysTick Counter register. - Configure the SysTick Counter clock source to be Core Clock Source (HCLK). - Enable the SysTick Interrupt. - Start the SysTick Counter. 2. You can change the SysTick Clock source to be HCLK_Div8 by calling the SysTick_CLKSourceConfig(SysTick_CLKSource_HCLK_Div8) just after the SysTick_Config() function call. The SysTick_CLKSourceConfig() is defined inside the misc.c file. 3. You can change the SysTick IRQ priority by calling the NVIC_SetPriority(SysTick_IRQn,...) just after the SysTick_Config() function call. The NVIC_SetPriority() is defined inside the core_cm3.h file. 4. To adjust the SysTick time base, use the following formula:Reload Value = SysTick Counter Clock (Hz) x Desired Time base (s) - Reload Value is the parameter to be passed for SysTick_Config() function - Reload Value should not exceed 0xFFFFFF / 上面说得很清楚，我们只要调用SysTick_Config()函数，系统就为我们做了大量的事情。系统完成的事情如下所示: 1.该函数的参数就是预装值 2.中断设置成最低级别，并将计数寄存器清零。 3.配置SysTick的时钟为HCLK。（还可以是HCLK/8） 4.使能嘀嗒定时器的中断 5.开始计数。这么说来，只要调用了SysTick_Config()函数，连NVIC都不用去配置了，系统已经直接打开了中断，我们只要去填写中断向量表中的SysTick_Handler( )就行了，而且该函数的参数就是预装值。多方便！可以利用上面的道理来实现STM32F103的精确延时操作，如下所示：在User_systick.c中 / Includes ------------------------------------------------------------------/ #include "stm32f10x.h" static uint32_t TimingDelay; //HCLK当前为72MHz void delay_1ms(uint32_t delay_conter) { //-----72MHz/9000/8=1000Hz,因此即1ms产生定时中断 SysTick_Config((uint32_t)9000); SysTick_CLKSourceConfig(SysTick_CLKSource_HCLK_Div8); TimingDelay = delay_conter; while(TimingDelay!=0); } void delay_10us(uint32_t delay_conter) { //-----72MHz/90/8=100000Hz,因此即10us产生定时中断 SysTick_Config((uint32_t)90); SysTick_CLKSourceConfig(SysTick_CLKSource_HCLK_Div8); TimingDelay = delay_conter; while(TimingDelay!=0); } void TimingDelay_Decrement(void) { if (TimingDelay != 0x00) { TimingDelay--; } } 在stm32f10x_it.c中 /* * @brief This function handles SysTick Handler. * @param None * @retval None */ void SysTick_Handler(void) { TimingDelay_Decrement(); } 因此在main.c中可以使用诸如delay_1ms()，delay_1us()等函数来实现延时操作，延时的本质是系统定制中断。 0 本帖被以下淘专辑推荐: · STM32开发经验与技巧\|主题: 15, 订阅: 2
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