stm32F4 PB0输出TM3 PWM信号

首先，需要将PB0引脚配置为复用推挽输出模式，并将其对应到定时器3的通道3上。具体的配置代码如下：

// 使能GPIOB时钟
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);
// 使能定时器3时钟
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);

// 配置PB0为复用推挽输出模式
GPIO_InitTypeDef GPIO_InitStructure;
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
GPIO_Init(GPIOB, &GPIO_InitStructure);

// 将PB0对应到定时器3的通道3上
GPIO_PinAFConfig(GPIOB, GPIO_PinSource0, GPIO_AF_TIM3);

// 配置定时器3为PWM模式
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
TIM_TimeBaseStructure.TIM_Prescaler = 0; // 不分频
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseStructure.TIM_Period = 999; // PWM周期为1ms
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;
TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

// 配置定时器3通道3为PWM输出模式
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Disable;
TIM_OCInitStructure.TIM_Pulse = 500; // PWM占空比为50%
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_High;
TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Reset;
TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCNIdleState_Reset;
TIM_OC3Init(TIM3, &TIM_OCInitStructure);

// 启动定时器3
TIM_Cmd(TIM3, ENABLE);

上述代码会使PB0输出一个占空比为50%、周期为1ms的PWM信号。你可以通过修改`TIM_OCInitStructure.TIM_Pulse`来改变PWM的占空比。