编写代码通过串口调试助手发送0、1、2、3、4给STM32F407单片机的USART1，单片机根据收到的数字，利用高级定时器输出不同占空比的PWM波形，控制LED的亮度； STM32单片机要用中断的方式接收串口调试助手发来的数据。利用两个按键分别能够增强、减弱LED亮度等级，最暗不再减弱，最亮不再增强，按键动作检测也要用中断方式。

好的，这是一个基于串口通信和中断的STM32F407单片机控制LED亮度的程序。以下是程序的主要框架：

#include "stm32f4xx.h"
#include "stm32f4xx_hal.h"

#define LED_PIN GPIO_PIN_13
#define LED_PORT GPIOC

UART_HandleTypeDef huart1;
TIM_HandleTypeDef htim1;

uint8_t received_data = 0;
uint16_t pwm_value = 0;

void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_USART1_UART_Init(void);
static void MX_TIM1_Init(void);

void increase_brightness(void);
void decrease_brightness(void);

int main(void)
{
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_USART1_UART_Init();
  MX_TIM1_Init();

  while (1)
  {
    // 根据接收到的数字设置PWM占空比
    switch (received_data)
    {
    case '0':
      pwm_value = 0;
      break;
    case '1':
      pwm_value = 3277;  // 10% 占空比
      break;
    case '2':
      pwm_value = 6554;  // 20% 占空比
      break;
    case '3':
      pwm_value = 9831;  // 30% 占空比
      break;
    case '4':
      pwm_value = 13107; // 40% 占空比
      break;
    default:
      break;
    }

    // 更新PWM占空比
    __HAL_TIM_SET_COMPARE(&htim1, TIM_CHANNEL_1, pwm_value);
  }
}

void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
  // 接收到一个字节
  if (huart->Instance == USART1)
  {
    HAL_UART_Receive_IT(&huart1, &received_data, 1);
  }
}

void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin)
{
  // 检测到按键动作
  if (GPIO_Pin == GPIO_PIN_0)
  {
    increase_brightness();
  }
  else if (GPIO_Pin == GPIO_PIN_1)
  {
    decrease_brightness();
  }
}

void increase_brightness(void)
{
  // 增加PWM占空比
  if (pwm_value < 13107)
  {
    pwm_value += 3277; // 增加10% 占空比
    __HAL_TIM_SET_COMPARE(&htim1, TIM_CHANNEL_1, pwm_value);
  }
}

void decrease_brightness(void)
{
  // 减少PWM占空比
  if (pwm_value > 0)
  {
    pwm_value -= 3277; // 减少10% 占空比
    __HAL_TIM_SET_COMPARE(&htim1, TIM_CHANNEL_1, pwm_value);
  }
}

static void MX_TIM1_Init(void)
{
  TIM_ClockConfigTypeDef sClockSourceConfig = {0};
  TIM_MasterConfigTypeDef sMasterConfig = {0};
  TIM_OC_InitTypeDef sConfigOC = {0};

  htim1.Instance = TIM1;
  htim1.Init.Prescaler = 83;
  htim1.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim1.Init.Period = 65535;
  htim1.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  if (HAL_TIM_Base_Init(&htim1) != HAL_OK)
  {
    Error_Handler();
  }

  sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
  if (HAL_TIM_ConfigClockSource(&htim1, &sClockSourceConfig) != HAL_OK)
  {
    Error_Handler();
  }

  if (HAL_TIM_PWM_Init(&htim1) != HAL_OK)
  {
    Error_Handler();
  }

  sConfigOC.OCMode = TIM_OCMODE_PWM1;
  sConfigOC.Pulse = 0;
  sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
  sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
  if (HAL_TIM_PWM_ConfigChannel(&htim1, &sConfigOC, TIM_CHANNEL_1) != HAL_OK)
  {
    Error_Handler();
  }

  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim1, &sMasterConfig) != HAL_OK)
  {
    Error_Handler();
  }

  HAL_TIM_Base_Start(&htim1);
  HAL_TIM_PWM_Start(&htim1, TIM_CHANNEL_1);
}

static void MX_USART1_UART_Init(void)
{
  huart1.Instance = USART1;
  huart1.Init.BaudRate = 115200;
  huart1.Init.WordLength = UART_WORDLENGTH_8B;
  huart1.Init.StopBits = UART_STOPBITS_1;
  huart1.Init.Parity = UART_PARITY_NONE;
  huart1.Init.Mode = UART_MODE_TX_RX;
  huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart1.Init.OverSampling = UART_OVERSAMPLING_16;
  if (HAL_UART_Init(&huart1) != HAL_OK)
  {
    Error_Handler();
  }

  HAL_UART_Receive_IT(&huart1, &received_data, 1);
}

static void MX_GPIO_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};

  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOC_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(LED_PORT, LED_PIN, GPIO_PIN_RESET);

  /*Configure GPIO pin : PC13 */
  GPIO_InitStruct.Pin = LED_PIN;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(LED_PORT, &GPIO_InitStruct);

  /*Configure GPIO pins : PA0 PA1 */
  GPIO_InitStruct.Pin = GPIO_PIN_0 | GPIO_PIN_1;
  GPIO_InitStruct.Mode = GPIO_MODE_IT_FALLING;
  GPIO_InitStruct.Pull = GPIO_PULLUP;
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

  /* EXTI interrupt init*/
  HAL_NVIC_SetPriority(EXTI0_IRQn, 0, 0);
  HAL_NVIC_EnableIRQ(EXTI0_IRQn);
  HAL_NVIC_SetPriority(EXTI1_IRQn, 0, 0);
  HAL_NVIC_EnableIRQ(EXTI1_IRQn);
}

void Error_Handler(void)
{
  while (1)
  {
  }
}

void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

  /** Configure the main internal regulator output voltage 
  */
  __HAL_RCC_PWR_CLK_ENABLE();
  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);
  /** Initializes the CPU, AHB and APB busses clocks 
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLM = 25;
  RCC_OscInitStruct.PLL.PLLN = 336;
  RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
  RCC_OscInitStruct.PLL.PLLQ = 7;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }
  /** Initializes the CPU, AHB and APB busses clocks 
  */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_SYSCLK |
                                RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV4;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5) != HAL_OK)
  {
    Error_Handler();
  }
}

该程序首先初始化GPIO、UART和TIM模块，然后进入while循环进行串口接收和PWM输出。在接收到一个字节时，程序会根据接收到的数字设置PWM占空比，然后更新PWM输出。在按下按键时，程序会检测到中断并执行相应的函数，增加或减少PWM占空比，从而控制LED亮度。

需要注意的是，需要在HAL_UART_RxCpltCallback和HAL_GPIO_EXTI_Callback中调用HAL_UART_Receive_IT和HAL_GPIO_Exti_IRQHandler来重新启动UART和GPIO中断。此外，需要在MX_TIM1_Init函数中设置PWM占空比的初始值为0。

希望这个程序能够对您有所帮助！