stm32的p2.3口输出72MHz占空比为80%的方波

要让STM32的P2.3口输出72MHz占空比为80%的方波，可以使用定时器来实现。首先，需要将P2.3口配置为定时器的输出引脚，然后配置定时器的时钟源和分频器，使得定时器的时钟频率为72MHz。接着，配置定时器的计数器和自动重载寄存器，使得定时器的周期为1个周期。然后，再配置定时器的占空比，使得高电平的时间为一个周期的80%。最后，启动定时器，并在定时器中断中翻转P2.3口的输出电平，就可以输出72MHz占空比为80%的方波了。以下是一个简单的示例代码：

#include "stm32f10x.h"

void TIM2_IRQHandler(void)
{
    if (TIM_GetITStatus(TIM2, TIM_IT_Update) != RESET)
    {
        TIM_ClearITPendingBit(TIM2, TIM_IT_Update);
        GPIO_WriteBit(GPIOB, GPIO_Pin_3, (BitAction)(1 - GPIO_ReadOutputDataBit(GPIOB, GPIO_Pin_3)));
    }
}

int main(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
    TIM_OCInitTypeDef TIM_OCInitStructure;
    NVIC_InitTypeDef NVIC_InitStructure;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, 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(GPIOB, &GPIO_InitStructure);

    TIM_TimeBaseStructure.TIM_Period = 1;
    TIM_TimeBaseStructure.TIM_Prescaler = 0;
    TIM_TimeBaseStructure.TIM_ClockDivision = 0;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

    TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_Pulse = 1 * 0.8; // 80% duty cycle
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
    TIM_OC1Init(TIM2, &TIM_OCInitStructure);

    TIM_ITConfig(TIM2, TIM_IT_Update, ENABLE);

    NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn;
    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStructure);

    TIM_Cmd(TIM2, ENABLE);

    while (1)
    {
    }
}