STM32F103C8T6设置系统时钟为72MHz，定时器3和定时器2输出440HzPWM标准库代码

以下是使用标准库代码在STM32F103C8T6上设置系统时钟为72MHz，并且配置定时器3和定时器2输出440Hz PWM信号的示例代码：

#include "stm32f10x.h"

void SystemClock_Config(void);
void TIM3_Config(void);
void TIM2_Config(void);

int main(void)
{
    // 设置系统时钟为72MHz
    SystemClock_Config();
  
    // 初始化定时器3和定时器2
    TIM3_Config();
    TIM2_Config();

    // 启动定时器3和定时器2
    TIM_Cmd(TIM3, ENABLE);
    TIM_Cmd(TIM2, ENABLE);

    while (1)
    {
        // 主循环
    }
}

void SystemClock_Config(void)
{
    RCC_DeInit();

    RCC_HSEConfig(RCC_HSE_ON);
    if (RCC_WaitForHSEStartUp() == SUCCESS)
    {
        RCC_PLLConfig(RCC_PLLSource_HSE_Div1, 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_Div2);
  
    SystemCoreClockUpdate();
}

void TIM3_Config(void)
{
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
    TIM_OCInitTypeDef TIM_OCInitStructure;
    GPIO_InitTypeDef GPIO_InitStructure;

    // 使能定时器3和GPIOB的时钟
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);

    // 配置GPIOB的引脚为复用推挽输出
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOB, &GPIO_InitStructure);

    // 设置定时器3的预分频值为72，计数频率为1MHz
    TIM_TimeBaseStructure.TIM_Period = 1000000 / 440 - 1;
    TIM_TimeBaseStructure.TIM_Prescaler = 72 - 1;
    TIM_TimeBaseStructure.TIM_ClockDivision = 0;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

    // 配置定时器3通道1的输出比较模式为PWM模式1
    TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
    TIM_OC1Init(TIM3, &TIM_OCInitStructure);

    // 设置定时器3通道1的占空比为50%
    TIM_SetCompare1(TIM3, (1000000 / 440 - 1) / 2);

    // 使能定时器3
    TIM_Cmd(TIM3, ENABLE);
}

void TIM2_Config(void)
{
    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
    TIM_OCInitTypeDef TIM_OCInitStructure;
    GPIO_InitTypeDef GPIO_InitStructure;

    // 使能定时器2和GPIOA的时钟
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);

    // 配置GPIOA的引脚为复用推挽输出
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    // 设置定时器2的预分频值为72，计数频率为1MHz
    TIM_TimeBaseStructure.TIM_Period = 1000000 / 440 - 1;
    TIM_TimeBaseStructure.TIM_Prescaler = 72 - 1;
    TIM_TimeBaseStructure.TIM_ClockDivision = 0;
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

    // 配置定时器2通道1的输出比较模式为PWM模式1
    TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
    TIM_OC1Init(TIM2, &TIM_OCInitStructure);

    // 设置定时器2通道1的占空比为50%
    TIM_SetCompare1(TIM2, (1000000 / 440 - 1) / 2);

    // 使能定时器2
    TIM_Cmd(TIM2, ENABLE);
}

这段代码首先配置系统时钟为72MHz，然后初始化定时器3和定时器2，使其输出440Hz的PWM信号。你可以根据需要修改频率和占空比。注意，使用定时器3和定时器2输出PWM信号时，需要分别配置不同的引脚和定时器。