编写代码基于stm32f407设计通过串口调试助手发送0，1，2，3，4给stm32f407串口1，单片机利用定时器输出不同占空比的pwm波形控制LED不同亮度

好的，这是一个比较具体的问题，需要编写一些代码来实现。下面是一个基本的代码框架，你可以根据具体需求进行修改：

#include "stm32f4xx.h"
#include "stm32f4xx_usart.h"
#include "stm32f4xx_gpio.h"
#include "stm32f4xx_tim.h"

#define LED_PIN GPIO_Pin_13
#define LED_GPIO_PORT GPIOG
#define LED_GPIO_CLK RCC_AHB1Periph_GPIOG

USART_InitTypeDef USART_InitStructure;
GPIO_InitTypeDef GPIO_InitStructure;
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;

void USART_Configuration(void)
{
  USART_InitTypeDef USART_InitStructure;
  GPIO_InitTypeDef GPIO_InitStructure;

  RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1, ENABLE);
  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);

  GPIO_PinAFConfig(GPIOA, GPIO_PinSource9, GPIO_AF_USART1);
  GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_USART1);

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9 | GPIO_Pin_10;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
  GPIO_Init(GPIOA, &GPIO_InitStructure);

  USART_InitStructure.USART_BaudRate = 115200;
  USART_InitStructure.USART_WordLength = USART_WordLength_8b;
  USART_InitStructure.USART_StopBits = USART_StopBits_1;
  USART_InitStructure.USART_Parity = USART_Parity_No;
  USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
  USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;

  USART_Init(USART1, &USART_InitStructure);
  USART_Cmd(USART1, ENABLE);
}

void LED_Configuration(void)
{
  GPIO_InitTypeDef GPIO_InitStructure;

  RCC_AHB1PeriphClockCmd(LED_GPIO_CLK, ENABLE);

  GPIO_InitStructure.GPIO_Pin = LED_PIN;
  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_NOPULL;
  GPIO_Init(LED_GPIO_PORT, &GPIO_InitStructure);

  GPIO_PinAFConfig(LED_GPIO_PORT, GPIO_PinSource13, GPIO_AF_TIM4);
}

void TIM_Configuration(void)
{
  TIM_TimeBaseStructure.TIM_Period = 1000 - 1;
  TIM_TimeBaseStructure.TIM_Prescaler = 8400 - 1; // 10kHz
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure);

  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = 0;
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
  TIM_OC1Init(TIM4, &TIM_OCInitStructure);

  TIM_Cmd(TIM4, ENABLE);
}

void TIM_SetDutyCycle(uint16_t duty_cycle)
{
  TIM_OCInitStructure.TIM_Pulse = duty_cycle;
  TIM_OC1Init(TIM4, &TIM_OCInitStructure);
}

int main(void)
{
  uint8_t data = 0;

  USART_Configuration();
  LED_Configuration();
  TIM_Configuration();

  while (1)
  {
    if (USART_GetFlagStatus(USART1, USART_FLAG_RXNE) == SET)
    {
      data = USART_ReceiveData(USART1);

      switch (data)
      {
      case '0':
        TIM_SetDutyCycle(0);
        break;
      case '1':
        TIM_SetDutyCycle(250);
        break;
      case '2':
        TIM_SetDutyCycle(500);
        break;
      case '3':
        TIM_SetDutyCycle(750);
        break;
      case '4':
        TIM_SetDutyCycle(1000);
        break;
      default:
        break;
      }

      USART_SendData(USART1, data);
    }
  }
}

代码中使用了串口1作为输入，接收从串口调试助手发送的数据。根据接收到的数据，设置不同的PWM占空比，控制LED的亮度。其中，TIM4作为定时器，用来输出PWM波形。

需要注意的是，代码中使用的是GPIOG的13号引脚作为LED的控制引脚。如果需要修改，需要相应地修改代码中的宏定义。

此外，在使用本代码之前，还需要配置STM32F407的相关硬件和软件环境，具体步骤可以参考相关文档和教程。