STM32F407最小系统板TIM5_CH2输出不了PWM

609959998

#include "sys.h"
#include "pwm.h"

void TIMx_PWM_Init(u32 arr,u32 psc)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
    TIM_OCInitTypeDef TIM_OCInitStructure;

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM5, ENABLE);
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);

    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;
    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(GPIOA, &GPIO_InitStructure);

    GPIO_PinAFConfig(GPIOA, GPIO_PinSource1, GPIO_AF_TIM5);

    TIM_TimeBaseStructure.TIM_Prescaler = psc;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseStructure.TIM_Period = arr;
    TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_TimeBaseInit(TIM5, &TIM_TimeBaseStructure);

    TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
    TIM_OC2Init(TIM5, &TIM_OCInitStructure);

    TIM_OC2PreloadConfig(TIM5, TIM_OCPreload_Enable);

    TIM_ARRPreloadConfig(TIM5, ENABLE);

    TIM_Cmd(TIM5, ENABLE);

}

int main(void)
{
        u16 led0pwmval=0;   
        u8 dir=1;
        delay_init(168);  //初始化延时函数
        uart_init(115200);//初始化串口波特率为115200

    TIMx_PWM_Init(500-1, 84-1);        //84M/84=1Mhz的计数频率,重装载值500，所以PWM频率为 1M/500=2Khz.     



   while(1)
        {

        }
}