目录
一、PWM原理
二、stm32 PWM资源
三、输出模式
1.模式1
2.模式2
四、PWM周期与频率
五、PWM占空比
六、PWM配置
七、 main.c代码
一、PWM原理
PWM，是脉冲宽度调制，它是通过对一系列脉冲的宽度进行调制，等效出所需要的波形（包含形状以及幅值），对模拟信号电平进行数字编码，也就是说通过调节占空比的变化来调节信号、能量等的变化，占空比就是指在一个周期内，信号处于有效电平的时间占据整个信号周期的百分比。
二、stm32 PWM资源
1.芯片 STM32F103C8T6 的PWM资源
高级定时器（TIM1）：7路
7路 通用定时器（TIM2~TIM4）：各4路
一共19路
2.PWM所在引脚
查看芯片手册，哪个引脚具有PWM且连接到哪个定时器的哪一路
三、输出模式
1.模式1
在向上计数时，一旦 CNT < CCRx 时输出为有效电平，否则为无效电平；
在向 下计数时，一旦 CNT < CCRx 时输出为有效电平，否则为无效电平。
2.模式2
在向上计数时，一旦 CNT < CCRx 时输出为无效电平，否则为有效电平；
在向下计数时，一旦 CNT < CCRx 时输出为无效电平，否则为有效电平。
四、PWM周期与频率
五、PWM占空比
由TIMx_CCRx寄存器决定。
六、PWM配置
1.时钟72MHz
2.对PB8（灯）输出PWM，呼吸灯
3.设置PWM
文章来源：https://www.toymoban.com/news/detail-625200.html
七、 main.c代码
呼吸灯文章来源地址https://www.toymoban.com/news/detail-625200.html
/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file : main.c
* @brief : Main program body
******************************************************************************
* @attention
*
* Copyright (c) 2023 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 "main.h"
#include "tim.h"
#include "gpio.h"
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
/* USER CODE END Includes */
/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */
/* USER CODE END PTD */
/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
/* USER CODE END PD */
/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */
/* USER CODE END PM */
/* Private variables ---------------------------------------------------------*/
/* USER CODE BEGIN PV */
/* USER CODE END PV */
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
/* USER CODE BEGIN PFP */
/* USER CODE END PFP */
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
/* USER CODE END 0 */
/**
* @brief The application entry point.
* @retval int
*/
int main(void)
{
/* USER CODE BEGIN 1 */
//定义==========================================================================
uint16_t pwmVal=0; //调整PWM占空比
uint8_t dir=1; //设置改变方向。1：占空比越来越大；0：占空比越来越小
/* USER CODE END 1 */
/* MCU Configuration--------------------------------------------------------*/
/* Reset of all peripherals, Initializes the Flash interface and the Systick. */
HAL_Init();
/* USER CODE BEGIN Init */
/* USER CODE END Init */
/* Configure the system clock */
SystemClock_Config();
/* USER CODE BEGIN SysInit */
/* USER CODE END SysInit */
/* Initialize all configured peripherals */
MX_GPIO_Init();
MX_TIM4_Init();
/* USER CODE BEGIN 2 */
// 启动使能 Timer4 第3通道 PWM 输出============================================
HAL_TIM_PWM_Start(&htim4,TIM_CHANNEL_3);//参数：定时器几，第几个通道
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
/* USER CODE END WHILE */
//=====================================================================
HAL_Delay(1);
if (dir)//如果是1
pwmVal++;//低电平占空比逐渐变大 灯变亮
else//如果是0
pwmVal--;//低电平占空比逐渐变大 灯变暗
if (pwmVal > 500)//达到最亮
dir = 0;//反转反向 让灯开始变暗
if (pwmVal == 0)//达到最暗
dir =1;
//修改比较值pwmalL，修改占空比
__HAL_TIM_SetCompare(&htim4, TIM_CHANNEL_3, pwmVal);
/* USER CODE BEGIN 3 */
}
/* USER CODE END 3 */
}
/**
* @brief System Clock Configuration
* @retval None
*/
void SystemClock_Config(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct = {0};
RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
/** 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.HSIState = RCC_HSI_ON;
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();
}
}
/* USER CODE BEGIN 4 */
/* USER CODE END 4 */
/**
* @brief This function is executed in case of error occurrence.
* @retval None
*/
void Error_Handler(void)
{
/* USER CODE BEGIN Error_Handler_Debug */
/* User can add his own implementation to report the HAL error return state */
__disable_irq();
while (1)
{
}
/* USER CODE END Error_Handler_Debug */
}
#ifdef USE_FULL_ASSERT
/**
* @brief Reports the name of the source file and the source line number
* where the assert_param error has occurred.
* @param file: pointer to the source file name
* @param line: assert_param error line source number
* @retval None
*/
void assert_failed(uint8_t *file, uint32_t line)
{
/* USER CODE BEGIN 6 */
/* User can add his own implementation to report the file name and line number,
ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
/* USER CODE END 6 */
}
#endif /* USE_FULL_ASSERT */
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