使用stm32f103c8t6 PA4实现PWM呼吸灯

以下是基于STM32CubeMX和Keil编译器的代码示例，使用PA4实现PWM呼吸灯：

1. 在CubeMX中设置PA4为TIM3的CH1输出引脚
2. 开启TIM3的PWM模式并设置时钟为72MHz，周期为200（约5kHz），占空比为0
3. 在main函数中初始化TIM3，并在while循环中不断改变TIM3的占空比以实现呼吸灯效果

/* Includes ------------------------------------------------------------------*/
#include "main.h"
#include "stm32f1xx_hal.h"

/* Private variables ---------------------------------------------------------*/
TIM_HandleTypeDef htim3;

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_TIM3_Init(void);

int main(void)
{
  /* MCU Configuration--------------------------------------------------------*/

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* Configure the system clock */
  SystemClock_Config();

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_TIM3_Init();

  /* Infinite loop */
  while (1)
  {
    for (int i = 0; i < 100; i++)
    {
      TIM3->CCR1 = i;
      HAL_Delay(10); // 延时一段时间，控制呼吸速度
    }
    for (int i = 100; i > 0; i--)
    {
      TIM3->CCR1 = i;
      HAL_Delay(10);
    }
  }
}

/** System Clock Configuration
*/
void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct;
  RCC_ClkInitTypeDef RCC_ClkInitStruct;

  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.HSEPredivValue = RCC_HSE_PREDIV_DIV1;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL9;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    Error_Handler();
  }

  /** Initializes the CPU, AHB and APB buses 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_DIV2;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
  {
    Error_Handler();
  }
}

/* TIM3 init function */
void MX_TIM3_Init(void)
{
  TIM_ClockConfigTypeDef sClockSourceConfig = {0};
  TIM_MasterConfigTypeDef sMasterConfig = {0};
  TIM_OC_InitTypeDef sConfigOC = {0};

  htim3.Instance = TIM3;
  htim3.Init.Prescaler = 719; // 时钟分频，72MHz/720=100kHz
  htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim3.Init.Period = 200; // 设置周期，每5kHz更新一次
  htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  if (HAL_TIM_PWM_Init(&htim3) != HAL_OK)
  {
    Error_Handler();
  }

  sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
  if (HAL_TIM_ConfigClockSource(&htim3, &sClockSourceConfig) != HAL_OK)
  {
    Error_Handler();
  }

  if (HAL_TIM_PWM_Start(&htim3, TIM_CHANNEL_1) != HAL_OK)
  {
    Error_Handler();
  }

  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig) != HAL_OK)
  {
    Error_Handler();
  }

  sConfigOC.OCMode = TIM_OCMODE_PWM1;
  sConfigOC.Pulse = 0; // 初始化占空比为0
  sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
  sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
  if (HAL_TIM_PWM_ConfigChannel(&htim3, &sConfigOC, TIM_CHANNEL_1) != HAL_OK)
  {
    Error_Handler();
  }
}

/** Configure pins as
        * Analog
        * Input Floating
        * Output Push Pull
        * Output Open Drain
        * Pull Up
        * Pull Down
        * Input Pull Up
        * Input Pull Down
        * EXTI
*/
void MX_GPIO_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};

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

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(GPIOA, GPIO_PIN_4, GPIO_PIN_RESET);

  /*Configure GPIO pin : PA4 */
  GPIO_InitStruct.Pin = GPIO_PIN_4;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
}

void Error_Handler(void)
{
  /* User can add his own implementation to report the HAL error return state */
  while (1)
  {
  }
}

在以上代码的while循环中，通过for循环改变TIM3的CCR1寄存器的值来改变PWM占空比，从而实现呼吸灯效果。每次改变占空比的循环时间间隔可以通过调整延时时间来控制。在此代码示例中，延时时间为10毫秒。