很多人遇到这种问题,但是应该注意的是PB4在单片机复位后,它是作为JTAG引脚来使用的,也就是说,要使用PB4你需要自己将其配置成普通GPIO,GPIO_PinRemapConfig(GPIO_Remap_SWJ_JTAGDisable,ENABLE);
配置成普通GPIO后,需要进行部分重映射,GPIO_PinRemapConfig(GPIO_PartialRemap_TIM3 , ENABLE);
两步都完成后即可得到正常的PWM波输出,下面附上完整PWM配置程序
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
GPIO_InitTypeDef GPIO_InitStructure;
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB | RCC_APB2Periph_AFIO, ENABLE);
GPIO_PinRemapConfig(GPIO_Remap_SWJ_JTAGDisable,ENABLE);
GPIO_PinRemapConfig(GPIO_PartialRemap_TIM3 , ENABLE);
GPIO_InitStructure.GPIO_Pin =GPIO_Pin_4|GPIO_Pin_5;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_Init(GPIOB, &GPIO_InitStructure);
TIM_TimeBaseStructure.TIM_Period = arr;
TIM_TimeBaseStructure.TIM_Prescaler =psc;
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
TIM_OCInitStructure.TIM_Pulse = 333;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OC1Init(TIM3, &TIM_OCInitStructure);
TIM_OC1PreloadConfig(TIM3, TIM_OCPreload_Enable);
TIM_OC2Init(TIM3, &TIM_OCInitStructure);
TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Enable);
TIM_ARRPreloadConfig(TIM3, ENABLE);
TIM_Cmd(TIM3, ENABLE);