写一个 STM32F103C8T6 控制按键切换不同占空比pwm波的代码

### 回答1：
STM32F103C8T6 可以使用定时器（Timer）生成 PWM 波，控制不同占空比的方法是改变计数比，即计数器加载值。按键切换占空比就可以通过改变定时器计数比来实现。

以下是 STM32F103C8T6 在 Keil uVision 开发环境下使用 C 语言实现的代码示例：

#include "stm32f10x.h"

#define PWM_Period 1000-1

void Delay(__IO uint32_t nTime);
void Timer_Config(void);
void GPIO_Config(void);

TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
TIM_OCInitTypeDef  TIM_OCInitStructure;
GPIO_InitTypeDef GPIO_InitStructure;

int main(void)
{
    SystemInit();
    GPIO_Config();
    Timer_Config();
    
    while(1)
    {
        // 检测按键是否按下
        if(GPIO_ReadInputDataBit(GPIOA, GPIO_Pin_0) == 0)
        {
            // 如果按键按下，则改变占空比
            TIM_OCInitStructure.TIM_Pulse = PWM_Period / 2;
            TIM_OC2Init(TIM2, &TIM_OCInitStructure);
            TIM_OC2PreloadConfig(TIM2, TIM_OCPreload_Enable);
        }
        else
        {
            // 如果按键没有按下，则恢复默认占空比
            TIM_OCInitStructure.TIM_Pulse = PWM_Period / 4;
            TIM_OC2Init(TIM2, &TIM_OCInitStructure);
            TIM_OC2PreloadConfig(TIM2, TIM_OCPreload_Enable);
        }
    }
}

void GPIO_Config(void)
{
    // 打开 PA0 的时钟
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);

    // 配置 PA0 为输入模式
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
    GPIO_InitStructure.GPIO_Mode =  

### 回答2：
以下是一个使用STM32F103C8T6控制按键切换不同占空比PWM波的代码示例：

#include "stm32f10x.h"

GPIO_InitTypeDef GPIO_InitStructure;
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
NVIC_InitTypeDef NVIC_InitStructure;

void GPIO_Configuration(void)
{
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
  
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU;
  GPIO_Init(GPIOA, &GPIO_InitStructure);
  
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
  GPIO_Init(GPIOA, &GPIO_InitStructure);
}

void TIM_Configuration(void)
{
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1, ENABLE);
  
  TIM_TimeBaseStructure.TIM_Prescaler = 72;
  TIM_TimeBaseStructure.TIM_Period = 1000-1;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
  TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);
  
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = 500; //初始占空比设为50%
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
  TIM_OC1Init(TIM1, &TIM_OCInitStructure);
  
  TIM_OC1PreloadConfig(TIM1, TIM_OCPreload_Enable);
  TIM_ARRPreloadConfig(TIM1, ENABLE);
  
  TIM_Cmd(TIM1, ENABLE);
}

void NVIC_Configuration(void)
{
  NVIC_InitStructure.NVIC_IRQChannel = EXTI0_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);
}

void EXTI0_IRQHandler(void)
{
  if(EXTI_GetITStatus(EXTI_Line0) == SET)
  {
    if(TIM_GetCounter(TIM1) == 0)
    {
      TIM_SetCompare1(TIM1, 750); //按键按下时将占空比切换为75%
    }
    else
    {
      TIM_SetCompare1(TIM1, 250); //按键释放时将占空比切换为25%
    }
    EXTI_ClearITPendingBit(EXTI_Line0);
  }
}

int main(void)
{
  GPIO_Configuration();
  TIM_Configuration();
  NVIC_Configuration();
  
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);
  GPIO_EXTILineConfig(GPIO_PortSourceGPIOA, GPIO_PinSource0);
  
  EXTI_InitTypeDef EXTI_InitStructure;
  EXTI_InitStructure.EXTI_Line = EXTI_Line0;
  EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;
  EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Falling | EXTI_Trigger_Rising;
  EXTI_InitStructure.EXTI_LineCmd = ENABLE;
  EXTI_Init(&EXTI_InitStructure);
  
  while(1)
  {
    // 程序主循环
  }
}  

### 回答3：
#include "stm32f103c8t6.h"

#define PWM_FREQ 100
#define MAX_DUTY_CYCLE 100

int main(void) {
    // 初始化按键和PWM引脚
    // Set GPIO_Pin_0 as input for the button
    GPIOA->CRL &= ~(GPIO_CRL_MODE0 | GPIO_CRL_CNF0);
    GPIOA->CRL |= GPIO_CRL_CNF0_1;
  
    // Set GPIO_Pin_1 as PWM output
    GPIOA->CRL &= ~(GPIO_CRL_MODE1 | GPIO_CRL_CNF1);
    GPIOA->CRL |= GPIO_CRL_MODE1 | GPIO_CRL_CNF1_1;
  
    // 初始化定时器和PWM模式
    RCC->APB2ENR |= RCC_APB2ENR_IOPAEN;
    RCC->APB1ENR |= RCC_APB1ENR_TIM2EN;
  
    TIM2->PSC = SystemCoreClock / (PWM_FREQ * MAX_DUTY_CYCLE) - 1;
    TIM2->ARR = MAX_DUTY_CYCLE - 1;
  
    // 启动定时器
    TIM2->CR1 = TIM_CR1_ARPE | TIM_CR1_CEN;
  
    int duty_cycle = 0;
    while (1) {
        // 检测按键是否按下
        if (GPIOA->IDR & GPIO_IDR_IDR0) {
            // 延时一段时间以消除按键抖动
            volatile int delay = 10000;
            while (delay--);
            
            // 如果按键仍然按下，增加占空比
            if (GPIOA->IDR & GPIO_IDR_IDR0) {
                duty_cycle += 10;
                if (duty_cycle > MAX_DUTY_CYCLE) {
                    duty_cycle = 0;  // 重置占空比
                }
                
                // 更新 PWM 的占空比
                TIM2->CCR1 = duty_cycle;
                
                // 延时一段时间以防止过快切换占空比
                delay = 10000;
                while (delay--);
            }
        }
    }
    return 0;
}