要将代码中的定时器通道从 TIM_CHANNEL_2 更改为 TIM_CHANNEL_3，您需要在相关配置的地方进行相应的修改。以下是更新后的代码：

/* USER CODE BEGIN Header */
/**
  ******************************************************************************
  * @file    tim.c
  * @brief   This file provides code for the configuration
  *          of the TIM instances.
  ******************************************************************************
  * @attention
  *
  * Copyright (c) 2025 STMicroelectronics.
  * All rights reserved.
  *
  * This software is licensed under terms that can be found in the LICENSE file
  * in the root directory of this software component.
  * If no LICENSE file comes with this software, it is provided AS-IS.
  *
  ******************************************************************************
  */
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "tim.h"
/* USER CODE BEGIN 0 */
/* USER CODE END 0 */
TIM_HandleTypeDef htim3;
/* TIM3 init function */
void MX_TIM3_Init(void)
{
    /* USER CODE BEGIN TIM3_Init 0 */
    /* USER CODE END TIM3_Init 0 */
    TIM_MasterConfigTypeDef sMasterConfig = {0};
    TIM_OC_InitTypeDef sConfigOC = {0};
    /* USER CODE BEGIN TIM3_Init 1 */
    /* USER CODE END TIM3_Init 1 */
    htim3.Instance = TIM3;
    htim3.Init.Prescaler = 71;
    htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
    htim3.Init.Period = 999;
    htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
    htim3.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
    
    if (HAL_TIM_PWM_Init(&htim3) != HAL_OK)
    {
        Error_Handler();
    }
    
    sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
    sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
    if (HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig) != HAL_OK)
    {
        Error_Handler();
    }
    
    // Change here: from CHANNEL_2 to CHANNEL_3
    sConfigOC.OCMode = TIM_OCMODE_PWM1;
    sConfigOC.Pulse = 500; 
    sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH; 
    sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
   // Update channel configuration to use Channel 3 instead of Channel2
   if (HAL_TIM_PWM_ConfigChannel(&htim3, &sConfigOC, TIM_CHANNEL_3) != HAL_OK)
   {
       Error_Handler();
   }
   /* USER CODE BEGIN TIM3_Init 2 */
   /* USER CODE END TIM3_Init 2 */
   
   HAL_TIM_MspPostInit(&htim3);
}
void HAL_TIM_PWM_MspInit(TIM_HandleTypeDef* tim_pwmHandle)
{
  
     if(tim_pwmHandle->Instance==TIM3)
     {
      /* USER CODE BEGIN TIM3_MspInit 0 */
      /* USER CODE END TIM3_MspInit 0 */
        /* TIM3 clock enable */
        __HAL_RCC_TIM3_CLK_ENABLE();
      /* USER CODE BEGIN TIM3_MspInit 1 */
      /* USER CODE END TIM3_MspInit 1 */
     }
}
void HAL_TIM_MspPostInit(TIM_HandleTypeDef* timHandle)
{
  
     GPIO_InitTypeDef GPIO_InitStruct = {0};
     
     if(timHandle->Instance==TIM3)
     {
      /* USER CODE BEGIN TIM3_MspPostInit 0 */
      /* USER CODE END TIM3_MspPostInit 0 */
        
         __HAL_RCC_GPIOA_CLK_ENABLE();
         
         /**TIM4 GPIO Configuration
          PA7     ------> TIM4_CH2 (修改为对应的引脚，假设为PA7）
          */
         GPIO_InitStruct.Pin = GPIO_PIN_7; // 修改这里以匹配实际通道引脚，根据您的硬件来选择正确的引脚。
         GPIO_InitStruct.Mode = GPIO_MODE_AF_PP; 
         GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW; 
         HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
      /* USER CODE BEGIN TIM4_MspPostInit 
      }
}
void HAL_TIM_PWM_MspDeInit(TIM_HandleTypeDef* tim_pwmHandle)
{
     if(tim_pwmHandle->Instance==TIM4) // 注意更新名称至.TIM4
     {
      /* 用户代码开始 Deinit部分用户代码 */
// Peripheral clock disable
__HAL_RCC_TIMER4_CLK_DISABLE(); 
/* 用户代码结束 Deinit部分用户代码*/
}
}
/* 用户代码开始部分 */
/* 用户代码结束部分 */

注意事项：

1. GPIO 引脚：确保您更改了引脚设置，以匹配 TIM_CHANNEL_03 对应的引脚。如果您使用的是 STM32 微控制器，请查阅手册以确认哪个引脚与此通道相连。
2. 其他配置：如果还有其它地方引用到通道或初始化，需确保同步更新。

希望这对你有帮助！


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