关于rtthread 4.0.0版本中pwm的初始化定时器寄存器读写问题

发布于 2019-02-27 09:43:47 浏览：2022 订阅该版

最近在使用rtthread中的pwm，系统版本4.0.0，bsp中使用的是stm32f107，在调试过程中，发现定时器寄存器在初始化时，不能进行读写。后来仔细看了下，才发现问题所在：也就是底层硬件初始化时，先进行相关寄存器初始化，然后在开相关时钟，代码如下(以通用定时器4为例)：
 TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
    TIM_OCInitTypeDef  TIM_OCInitStructure;

//Init TIM4
    TIM_TimeBaseStructure.TIM_Period = 0;  
    TIM_TimeBaseStructure.TIM_Prescaler = 0;  
    TIM_TimeBaseStructure.TIM_ClockDivision = 0;  
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;   
    TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure);

TIM_SelectOutputTrigger(TIM4, TIM_TRGOSource_Reset);
    TIM_SelectMasterSlaveMode(TIM4, TIM_MasterSlaveMode_Disable);

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1; 
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; 
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low; 
#ifdef BSP_USING_PWM4_CH1
    TIM_OC1Init(TIM4, &TIM_OCInitStructure); 
    TIM_OC1PreloadConfig(TIM4, TIM_OCPreload_Enable);   
#endif /* BSP_USING_PWM4_CH1 */

#ifdef BSP_USING_PWM4_CH2
    TIM_OC2Init(TIM4, &TIM_OCInitStructure); 
    TIM_OC2PreloadConfig(TIM4, TIM_OCPreload_Enable);   
#endif /* BSP_USING_PWM3_CH2 */

#ifdef BSP_USING_PWM4_CH3
    TIM_OC3Init(TIM4, &TIM_OCInitStructure); 
    TIM_OC3PreloadConfig(TIM4, TIM_OCPreload_Enable);   
#endif /* BSP_USING_PWM3_CH3 */

#ifdef BSP_USING_PWM4_CH4
    TIM_OC4Init(TIM4, &TIM_OCInitStructure); 
    TIM_OC4PreloadConfig(TIM4, TIM_OCPreload_Enable);   
#endif /* BSP_USING_PWM3_CH4 */

TIM_PWM_MspInit(TIM4);
    TIM_MspPostInit(TIM4);
    TIM_ARRPreloadConfig(TIM4, DISABLE);
    TIM_Cmd(TIM4, ENABLE);

以上代码为系统中自带了初始化代码，这样会导致初始化相关的寄存器不能进行读写。

修改后，能运行的代码如下(即把相关的时钟是能初始化提前)：
TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
    TIM_OCInitTypeDef  TIM_OCInitStructure;

TIM_PWM_MspInit(TIM4);
    TIM_MspPostInit(TIM4);

//Init TIM4
    TIM_TimeBaseStructure.TIM_Period = 0;  
    TIM_TimeBaseStructure.TIM_Prescaler = 0;  
    TIM_TimeBaseStructure.TIM_ClockDivision = 0;  
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;   
    TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure);

TIM_SelectOutputTrigger(TIM4, TIM_TRGOSource_Reset);
    TIM_SelectMasterSlaveMode(TIM4, TIM_MasterSlaveMode_Disable);

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1; 
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; 
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low; 
#ifdef BSP_USING_PWM4_CH1
    TIM_OC1Init(TIM4, &TIM_OCInitStructure); 
    TIM_OC1PreloadConfig(TIM4, TIM_OCPreload_Enable);   
#endif /* BSP_USING_PWM4_CH1 */

#ifdef BSP_USING_PWM4_CH2
    TIM_OC2Init(TIM4, &TIM_OCInitStructure); 
    TIM_OC2PreloadConfig(TIM4, TIM_OCPreload_Enable);   
#endif /* BSP_USING_PWM3_CH2 */

#ifdef BSP_USING_PWM4_CH3
    TIM_OC3Init(TIM4, &TIM_OCInitStructure); 
    TIM_OC3PreloadConfig(TIM4, TIM_OCPreload_Enable);   
#endif /* BSP_USING_PWM3_CH3 */

#ifdef BSP_USING_PWM4_CH4
    TIM_OC4Init(TIM4, &TIM_OCInitStructure); 
    TIM_OC4PreloadConfig(TIM4, TIM_OCPreload_Enable);   
#endif /* BSP_USING_PWM3_CH4 */

TIM_ARRPreloadConfig(TIM4, DISABLE);
    TIM_Cmd(TIM4, ENABLE);

以上描述只是针对pwm使用中，存在的一个关于底层外设初始化问题，因为没有过多在看其它部分的内容，所以不敢确定其它外设初始化是否也存在类似问题，不过同(童)学(鞋)们在使用的过程中，需要注意一下。