一个很简单的PWM生成程序，用的是Keil (MDK-ARM Version 3.20),程序运行一切正常，在PORTA的PIN3生成50%占空比的方波，程序如下：
RCC_HSICmd(ENABLE);
FLASH_SetLatency(FLASH_Latency_2);
FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);
RCC_PLLConfig(RCC_PLLSource_HSI_Div2, RCC_PLLMul_9);
RCC_PLLCmd(ENABLE);
while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET)
{
}
RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);
while(RCC_GetSYSCLKSource() != 0x08)
{
}
RCC_HCLKConfig(RCC_SYSCLK_Div1);
RCC_PCLK2Config(RCC_HCLK_Div1);
RCC_PCLK1Config(RCC_HCLK_Div4);
RCC_GetClocksFreq(&RCC_ClockFreq);
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA|RCC_APB2Periph_GPIOC, ENABLE);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOA, &GPIO_InitStructure);
/* Time base configuration */
TIM_TimeBaseStructure.TIM_Period = 1800;
TIM_TimeBaseStructure.TIM_Prescaler = 0x00;
TIM_TimeBaseStructure.TIM_ClockDivision = 0x0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
TIM_OCInitStructure.TIM_Channel = TIM_Channel_4; //********
TIM_OCInitStructure.TIM_Pulse = 900;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
TIM_OCInit(TIM2, &TIM_OCInitStructure); //********
TIM_OC4PreloadConfig(TIM2, TIM_OCPreload_Enable);
TIM_ARRPreloadConfig(TIM2, ENABLE);
/* TIM2 enable counter */
TIM_Cmd(TIM2, ENABLE);
升级Keil（MDK-ARM Version 3.20），编译报错，信息是：
“error: #136: struct "<unnamed>" has no field "TIM_Channel"”
检查STM的参考手册，发现STM改了库文件；TIM_OCInit不再存在，增加了TIM_OC1Init,TIM_OC2Init,TIM_OC3Init,TIM_OC4Init；TIM_OCInitStructure结构中不再有TIM_Channel；于是把程序中标有“//********”，改成如下：
........
// TIM_OCInitStructure.TIM_Channel = TIM_Channel_4;
.......
TIM_OC4Init(TIM2, &TIM_OCInitStructure);
编译通过，测试后发现计数器运行正常，但是在PORTA的PIN3没有方波生成。问题是程序没有什么改动，怎么会有这种结果呢？
花了好长时间都没有搞清楚原因，是Keil的问题还是STM的问题？ 或者是在新的库文件里，还需要进行其它的设置? |
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