最近在使用正点原子的阿波罗开发板做 tiM14的PWM输出实验  要求输出30Hz的。对比手册，TIM14挂在APB1上，APB时钟为54MHz，可实际使用中发现TIM14的时钟源输出的是432MHz，查看代码，只有在系统时钟初始化时将PLL设为432MHz，代码如下：
GPIO_InitTypeDef GPIO_Initure;
TIM_HandleTypeDef  TIM14_Handle;
TIM_OC_InitTypeDef TIM14_CH1Handle;       
__HAL_RCC_GPIOF_CLK_ENABLE();               
__HAL_RCC_TIM14_CLK_ENABLE();                                                               
       
GPIO_Initure.Pin=GPIO_PIN_9;                             //PF9  Ï½µÑØ´¥·¢£¬ÉÏÀ­
GPIO_Initure.Mode=GPIO_MODE_AF_PP;     //¸´ÓÃÍÆÍì
GPIO_Initure.Pull=GPIO_PULLUP;                                //ÉÏÀ­
GPIO_Initure.Alternate = GPIO_AF9_TIM14;
HAL_GPIO_Init(GPIOF,&GPIO_Initure);
                 
//base sconfig
TIM14_Handle.Instance = TIM14;
TIM14_Handle.Init.Period = 100;
TIM14_Handle.Init.ClockDivision = TIM_CLOCKDIVISION_DIV4;
TIM14_Handle.Init.Prescaler = (36000 - 1);
TIM14_Handle.Init.CounterMode = TIM_COUNTERMODE_UP;
TIM14_Handle.Init.RepetitionCounter = 0;  //ÂíÉϸüÐÂARR
HAL_TIM_Base_Init(&TIM14_Handle);
               
//OC config
TIM14_CH1Handle.OCMode=TIM_OCMODE_PWM1;
TIM14_CH1Handle.Pulse = 50;
TIM14_CH1Handle.OCPolarity=TIM_OCPOLARITY_HIGH;
HAL_TIM_PWM_ConfigChannel(&TIM14_Handle,&TIM14_CH1Handle,TIM_CHANNEL_1);
HAL_TIM_PWM_Start(&TIM14_Handle,TIM_CHANNEL_1);


432M/4/36000 = 3KHz  
计数100   刚好30Hz   示波器测量也是30Hz