STM32Cube_FW_F1_V1.0.0固件库学习(五) Systick

看了很久，总觉得不太对。。。原来新的库已经给你写好了。。。

直接调用HAL_Delay（time）就好

ST固件库给的配置顺序：

   (+) The HAL_SYSTICK_Config()function calls the SysTick_Config() function which
       is a CMSIS function that:
        (++) Configures the SysTick Reload register with value passed as function parameter.
        (++) Configures the SysTick IRQ priority to the lowest value (0x0F).
        (++) Resets the SysTick Counter register.
        (++) Configures the SysTick Counter clock source to be Core Clock Source (HCLK).
        (++) Enables the SysTick Interrupt.
        (++) Starts the SysTick Counter.

简单来说：

1.配置SYSTICK计数值

2.配置SYSTICK IRQ优先级为最低

3.复位SYSTICK计数器

4.配置SYSTICK计数时钟源

5.使能SYSTICK中断

6.启动SYSTICK计数器

那ST是怎么帮我们完成的呢？

看main函数：

在HAL_Init中，已经通过HAL_InitTick（SYSTICK_IRQ_Priority)完成了我们上面的前两步

HAL_StatusTypeDef HAL_Init(void)
{
  /* Configure Flash prefetch */
#if (PREFETCH_ENABLE != 0)
#if defined(STM32F101x6) || defined(STM32F101xB) || defined(STM32F101xE) || defined(STM32F101xG) || \
    defined(STM32F102x6) || defined(STM32F102xB) || \
    defined(STM32F103x6) || defined(STM32F103xB) || defined(STM32F103xE) || defined(STM32F103xG) || \
    defined(STM32F105xC) || defined(STM32F107xC)

  /* Prefetch buffer is not available on value line devices */
  __HAL_FLASH_PREFETCH_BUFFER_ENABLE();
#endif
#endif /* PREFETCH_ENABLE */

  /* Set Interrupt Group Priority */
  HAL_NVIC_SetPriorityGrouping(NVIC_PRIORITYGROUP_4);　　　　　　//为后面配置STYTICK IRQ做准备 先配置中断组号 全是主中断

  /* Use systick as time base source and configure 1ms tick (default clock after Reset is MSI) */
  HAL_InitTick(TICK_INT_PRIORITY);

  /* Init the low level hardware */
  HAL_MspInit();　　　　　　　　　　　　　　//用户定义 函数内未添加内容

  /* Return function status */
  return HAL_OK;
}

__weak HAL_StatusTypeDef HAL_InitTick(uint32_t TickPriority)
{
  /*Configure the SysTick to have interrupt in 1ms time basis*/
  HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);　　           //第一步 配置systick最小时钟片段 即SYSTICK的计数周期 1ms = 获取当前的系统时钟/1000

  /*Configure the SysTick IRQ priority */
  HAL_NVIC_SetPriority(SysTick_IRQn, TickPriority ,0);　　　　　　//第二步 配置SYSTICK优先级

   /* Return function status */
  return HAL_OK;
}

那完成这两步剩下的在哪里，看上面的main函数，就只有在SystemClock_Config()里面了

/** System Clock Configuration
*/
void SystemClock_Config(void)
{

  RCC_OscInitTypeDef RCC_OscInitStruct;
  RCC_ClkInitTypeDef RCC_ClkInitStruct;

  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSICalibrationValue = 16;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
  RCC_OscInitStruct.PLL2.PLL2State = RCC_PLL_NONE;
  HAL_RCC_OscConfig(&RCC_OscInitStruct);

  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_SYSCLK;       /*!< SYSCLK to configure */
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSI;    /*!< HSI selected as system clock */
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;        /*!< SYSCLK not divided */
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;         /*!< SYSCLK not divided */
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;         /*!< SYSCLK not divided */
  HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0);

}

在HAL_RCC_OscConfig()中，如下图红框处位置，就将系统计数器直接清0，然后在后面启用。开始刚上电的时候，应该是用的默认时钟源，