请问有没有知道这个程序有什么问题吗，下载到芯片一直没有PWM输出，不知道为什么，请教一下，谢谢。。。。

找到问题所在了 ，少下面这一句，添加后就好了，不光要使能定时器、GPIO,还要使能功能复用
RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);

官方例子看下

1. void TIM_Config(void)
   
2. {
   
3.   GPIO_InitTypeDef GPIO_InitStructure;
   
4.   
   
5.   /* TIM10 clock enable */
   
6.   RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM10, ENABLE);
   
7. 
   
8.   /* GPIOF clock enable */
   
9.   RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOF, ENABLE);
   
10.   
    
11.   /* GPIOF Configuration: TIM10 CH1 (PF6) */
    
12.   GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 ;
    
13.   GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
    
14.   GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
    
15.   GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
    
16.   GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP ;
    
17.   GPIO_Init(GPIOF, &GPIO_InitStructure);
    
18. 
    
19.   /* Connect TIM pins to AF3 */
    
20.   GPIO_PinAFConfig(GPIOF, GPIO_PinSource6, GPIO_AF_TIM10);
    
21. }

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1. int main(void)
   
2. {
   
3.   /*!< At this stage the microcontroller clock setting is already configured,
   
4.        this is done through SystemInit() function which is called from startup
   
5.        file (startup_stm32f2xx.s) before to branch to application main.
   
6.        To reconfigure the default setting of SystemInit() function, refer to
   
7.        system_stm32f2xx.c file
   
8.      */
   
9. 
   
10.   /* TIM Configuration */
    
11.   TIM_Config();
    
12.   
    
13.   /* ---------------------------------------------------------------------------
    
14.     TIM10 Configuration: generate 1 PWM signal:
    
15.    
    
16.     In this example TIM10 input clock (TIM10CLK) is set to 2 * APB2 clock (PCLK2),
    
17.     since APB2 prescaler is different from 1.   
    
18.       TIM10CLK = 2 * PCLK2  
    
19.       PCLK2 = HCLK / 2
    
20.       => TIM10CLK = HCLK = SystemCoreClock
    
21.          
    
22.     To get TIM10 counter clock at 20 MHz, the prescaler is computed as follows:
    
23.        Prescaler = (TIM10CLK / TIM10 counter clock) - 1
    
24.        Prescaler = (SystemCoreClock /20 MHz) - 1
    
25.                                              
    
26.     To get TIM10 output clock at 30 KHz, the period (TIM10_ARR) is computed as follows:
    
27.        ARR = (TIM10 counter clock / TIM10 output clock) - 1
    
28.            = 665
    
29.                   
    
30.     TIM10 Channel1 duty cycle = (TIM10_CCR1/ TIM10_ARR)* 100 = 50%
    
31. 
    
32.     Note:
    
33.      SystemCoreClock variable holds HCLK frequency and is defined in system_stm32f2xx.c file.
    
34.      Each time the core clock (HCLK) changes, user had to call SystemCoreClockUpdate()
    
35.      function to update SystemCoreClock variable value. Otherwise, any configuration
    
36.      based on this variable will be incorrect.   
    
37.   --------------------------------------------------------------------------- */   
    
38. 
    
39. 
    
40.   /* Compute the prescaler value */
    
41.   PrescalerValue = (uint16_t) (SystemCoreClock / 20000000) - 1;
    
42. 
    
43.   /* Time base configuration */
    
44.   TIM_TimeBaseStructure.TIM_Period = 665;
    
45.   TIM_TimeBaseStructure.TIM_Prescaler = PrescalerValue;
    
46.   TIM_TimeBaseStructure.TIM_ClockDivision = 0;
    
47.   TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    
48. 
    
49.   TIM_TimeBaseInit(TIM10, &TIM_TimeBaseStructure);
    
50. 
    
51.   /* PWM1 Mode configuration: Channel1 */
    
52.   TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
    
53.   TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
    
54.   TIM_OCInitStructure.TIM_Pulse = CCR1_Val;
    
55.   TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
    
56. 
    
57.   TIM_OC1Init(TIM10, &TIM_OCInitStructure);
    
58. 
    
59.   TIM_OC1PreloadConfig(TIM10, TIM_OCPreload_Enable);
    
60. 
    
61.   TIM_ARRPreloadConfig(TIM10, ENABLE);
    
62. 
    
63.   /* TIM10 enable counter */
    
64.   TIM_Cmd(TIM10, ENABLE);
    
65. 
    
66.   while (1)
    
67.   {}
    
68. }

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你的代码里面，是先执行PWMA=2000再执行配置定时器3，也就是说在执行PWMA=2000这条语句的时候定时器3的时钟没有打开，那么这时候向定时器3的CCR1寄存器的写是无效的。
建议在配置完定时器3后，再执行PWMA=2000，希望PWMA这个宏没有错

Period比Pulse小，就没有输出。

看你上面代码没有看到问题，你最好一步一步仿真看看到底怎么回事

从上面代码  看不出PWM输出函数

给你一个参考：
http://www.cnblogs.com/jiwangbujiu/p/5616376.html

问题暂未看出来。

IO模式后面设置过了，刚没看到

搞清楚实质. 脉宽 ,周期, 脉宽是通过match寄存器实现.

问题暂未看出来。

CCR1 = ??

直接使用CubeMX生成工程多简单

官方例子看下

我看的好像没啥问题啊

wenyangzeng 发表于 2017-5-5 07:25
Period比Pulse小，就没有输出。

你重新看 你看错了，人家设置的是对的