代码收藏家 STM32 定时器+延迟函数实验+PWM实验+超声波实验
一、定时器与时钟信号的关系
时钟树为定时器提供时钟信号，而定时器执行和事件相关的操作。
二、定时器的组成
1、时基单元
1.时钟来源
在这里我们考虑从时钟树来的时钟信号RCC
如果分频器的分频系数等于1，则后面的倍频器为1倍，如果分频器的分频系数大于1为2、3、4…….则倍频器应该x2为两倍。
2.预分频PSC
频率计算公式为
例如：
3.自动重装寄存器ARR和计数器CNT
作用对脉冲进行计数
4.重复计数器RCR
5.时基单元的补充知识
STM32F103内涵定时器1、2、3、4，其中1是F1系列的高级定时器有重复计数器RCR，2到4为通用定时器无RCR
寄存器预加载
以上框图中，预分频器PSC和自动重装寄存器ARR和重复计数器RCR方框都有一个阴影，而这个阴影就是寄存器的预加载机制，并且PSC和RCR的预加载机制是强制开启的，不可关闭，而ARR是可以手动开关默认关闭。
6.自制延迟函数实验
用定时器自制一个延迟1ms的延迟函数，使得板载led灯以1s为周期的时间闪烁
我们需要编写的两个函数
声明一个全局变量currentMiliSeconds来表示单片机的当前时间
要想要获得1ms的定时周期则配置如下：PSC设置为7，ARR设置为999，重复技术器RCC设置为0
并且记住将NVIC Settings中的updata interrupt 打开,
并且学会两种新的函数
main函数如下
/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file : main.c
* @brief : Main program body
******************************************************************************
* @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 "main.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 ---------------------------------------------------------*/
TIM_HandleTypeDef htim1;
/* USER CODE BEGIN PV */
static volatile uint32_t currentMiliSeconds=0;//当前单片机的时间
/* USER CODE END PV */
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_TIM1_Init(void);
/* USER CODE BEGIN PFP */
static void MyDelay(uint32_t Delay);//延迟函数
static uint32_t MyGetTick(void);//获取当前单片机的时间;
/* USER CODE END PFP */
/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
static void MyDelay(uint32_t Delay){
uint32_t expireTime=MyGetTick()+Delay;
while(MyGetTick()<expireTime){}
}
static uint32_t MyGetTick(){
return currentMiliSeconds;
}
void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
if(htim ==&htim1){
currentMiliSeconds++;
}
}
/* USER CODE END 0 */
/**
* @brief The application entry point.
* @retval int
*/
int main(void)
{
/* USER CODE BEGIN 1 */
/* 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_TIM1_Init();
/* USER CODE BEGIN 2 */
HAL_TIM_Base_Start_IT(&htim1);//以中断方式启动时基单兿
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{ HAL_GPIO_WritePin(GPIOC,GPIO_PIN_13,GPIO_PIN_RESET);
MyDelay(100);
HAL_GPIO_WritePin(GPIOC,GPIO_PIN_13,GPIO_PIN_SET);
MyDelay(100);
/* USER CODE END WHILE */
/* 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_HSI;
RCC_OscInitStruct.HSIState = RCC_HSI_ON;
RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
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_HSI;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
{
Error_Handler();
}
}
/**
* @brief TIM1 Initialization Function
* @param None
* @retval None
*/
static void MX_TIM1_Init(void)
{
/* USER CODE BEGIN TIM1_Init 0 */
/* USER CODE END TIM1_Init 0 */
TIM_ClockConfigTypeDef sClockSourceConfig = {0};
TIM_MasterConfigTypeDef sMasterConfig = {0};
/* USER CODE BEGIN TIM1_Init 1 */
/* USER CODE END TIM1_Init 1 */
htim1.Instance = TIM1;
htim1.Init.Prescaler = 7;
htim1.Init.CounterMode = TIM_COUNTERMODE_UP;
htim1.Init.Period = 999;
htim1.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
htim1.Init.RepetitionCounter = 0;
htim1.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_ENABLE;
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();
}
sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
if (HAL_TIMEx_MasterConfigSynchronization(&htim1, &sMasterConfig) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN TIM1_Init 2 */
/* USER CODE END TIM1_Init 2 */
}
/**
* @brief GPIO Initialization Function
* @param None
* @retval None
*/
static void MX_GPIO_Init(void)
{
GPIO_InitTypeDef GPIO_InitStruct = {0};
/* USER CODE BEGIN MX_GPIO_Init_1 */
/* USER CODE END MX_GPIO_Init_1 */
/* GPIO Ports Clock Enable */
__HAL_RCC_GPIOC_CLK_ENABLE();
__HAL_RCC_GPIOA_CLK_ENABLE();
/*Configure GPIO pin Output Level */
HAL_GPIO_WritePin(GPIOC, GPIO_PIN_13, GPIO_PIN_SET);
/*Configure GPIO pin : PC13 */
GPIO_InitStruct.Pin = GPIO_PIN_13;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_OD;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);
/* USER CODE BEGIN MX_GPIO_Init_2 */
/* USER CODE END MX_GPIO_Init_2 */
}
/* 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 */
2、输出比较单元
产生精确定时信号是输出比较
而要想实现输入捕获和输出比较，中间的CCR1比较寄存器起到关键作用。要想实现PWM脉冲输出，上面的时基单元决定了周期，CCR1就决定了占空比。
这样就得到PWM为80%的信号
而输出的值还受到模式选择和极性选择的作用
一共有以下几种模式选择
极性选择
3、PWM呼吸灯实验
实验要求：我们用STM32F103C8T6为核心板，使外界两个led灯呈现呼吸一样的闪烁。
亮度就是PWM的占空比，时间就是定时器当前的时间。
占空比的计算公式
则程序应该如下所示：
接线图如下：
几个函数
4、定时器输入捕获
1.什么是定时器的输入捕获
定时器的输入捕获是信号变化时通过CH1输入捕获然后读取CNT的值并保存到到CCR1；
输入捕获展开后为以下内部结构，拥有以下四个阶段：
2.超声波测距实验
超声波的使用原理是超声波模块给Trig一个大于10us的脉冲触发Echo发送一个上升沿，超声波发送出去后碰到障碍物反射回接收端，此时Echo为下降沿，而传播的时间就是脉宽的长度，距离为声速*传播时间/2。
在STM32中实现就是通过Echo连接一个CH1用上升沿脉冲直接的方法，CH2悬空用下降沿脉冲间接方式。
1.新建一个STM32CUBEMX工程，型号选择STM32F103C8T6；
2.按照以下接线图接线
3.配置定时器1
定时器1以每次1us的时钟进行计数最大计数约等于为65ms，通道1设置为直接上升沿脉冲模式，通道2设置为间接下降沿脉冲模式。
4.GPIO设置
PA0设置为推挽输出模式接超声波模块的Trig引脚，PC13连接板载led灯设置为开漏输出模式。
5.实现步骤
给Trig一个大于10us的脉冲信号触发超声波。当CC1标志位置1时表示超声波发送，CC2标志位置1时表示超声波接受到，此时停止计数器，计算Echo的脉宽
6.可能用到的部分函数
main函数代码如下：
/* USER CODE BEGIN Header */
/**
******************************************************************************
* @file : main.c
* @brief : Main program body
******************************************************************************
* @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 "main.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 ---------------------------------------------------------*/
TIM_HandleTypeDef htim1;
/* USER CODE BEGIN PV */
/* USER CODE END PV */
/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_TIM1_Init(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 */
/* 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_TIM1_Init();
/* USER CODE BEGIN 2 */
/* USER CODE END 2 */
/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
//1.清除cnt计数
__HAL_TIM_SET_COUNTER(&htim1,0);
//2.清楚cc1和cc2的标志位
__HAL_TIM_CLEAR_FLAG(&htim1,TIM_FLAG_CC1);
__HAL_TIM_CLEAR_FLAG(&htim1,TIM_FLAG_CC2);
//3.启动计数器
HAL_TIM_IC_Start(&htim1,TIM_CHANNEL_1);
HAL_TIM_IC_Start(&htim1,TIM_CHANNEL_2);
//4.给Trig一个大于10us的脉冲启动测量
HAL_GPIO_WritePin(GPIOA,GPIO_PIN_0,GPIO_PIN_SET);
for(int i=0;i<10;i++){}//延迟10us
HAL_GPIO_WritePin(GPIOA,GPIO_PIN_0,GPIO_PIN_RESET);
//5.等待测量结束
uint8_t success=0;//测量是否成功
uint32_t expiretime=HAL_GetTick()+50;//最长等待时间
while(expiretime>HAL_GetTick())
{
uint32_t cc1flag=__HAL_TIM_GET_FLAG(&htim1,TIM_FLAG_CC1);//cc1的标志位
uint32_t cc2flag=__HAL_TIM_GET_FLAG(&htim1,TIM_FLAG_CC2);//cc2的标志位
if(cc1flag&&cc2flag){//cc1标志位和cc2标志位都等于1
success=1;
break;
}
}
// 6.关闭定时器
HAL_TIM_IC_Stop(&htim1,TIM_CHANNEL_1);
HAL_TIM_IC_Stop(&htim1,TIM_CHANNEL_2);
//7.计算距离
if(success == 1){
uint32_t cc1=__HAL_TIM_GET_COMPARE(&htim1,TIM_CHANNEL_1);
uint32_t cc2=__HAL_TIM_GET_COMPARE(&htim1,TIM_CHANNEL_2);
float distance=(cc2-cc1)*1e-6*360.0f/2.0f;
//8.判断距离是否满足小于20cm，小于则点亮led灯
if(distance<=0.2)
{
HAL_GPIO_WritePin(GPIOC,GPIO_PIN_13,GPIO_PIN_RESET);
}
else
HAL_GPIO_WritePin(GPIOC,GPIO_PIN_13,GPIO_PIN_SET);
}
/* USER CODE END WHILE */
/* 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_HSI;
RCC_OscInitStruct.HSIState = RCC_HSI_ON;
RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_NONE;
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_HSI;
RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
{
Error_Handler();
}
}
/**
* @brief TIM1 Initialization Function
* @param None
* @retval None
*/
static void MX_TIM1_Init(void)
{
/* USER CODE BEGIN TIM1_Init 0 */
/* USER CODE END TIM1_Init 0 */
TIM_ClockConfigTypeDef sClockSourceConfig = {0};
TIM_MasterConfigTypeDef sMasterConfig = {0};
TIM_IC_InitTypeDef sConfigIC = {0};
/* USER CODE BEGIN TIM1_Init 1 */
/* USER CODE END TIM1_Init 1 */
htim1.Instance = TIM1;
htim1.Init.Prescaler = 7;
htim1.Init.CounterMode = TIM_COUNTERMODE_UP;
htim1.Init.Period = 65535;
htim1.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
htim1.Init.RepetitionCounter = 0;
htim1.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_ENABLE;
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_IC_Init(&htim1) != HAL_OK)
{
Error_Handler();
}
sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
if (HAL_TIMEx_MasterConfigSynchronization(&htim1, &sMasterConfig) != HAL_OK)
{
Error_Handler();
}
sConfigIC.ICPolarity = TIM_INPUTCHANNELPOLARITY_RISING;
sConfigIC.ICSelection = TIM_ICSELECTION_DIRECTTI;
sConfigIC.ICPrescaler = TIM_ICPSC_DIV1;
sConfigIC.ICFilter = 0;
if (HAL_TIM_IC_ConfigChannel(&htim1, &sConfigIC, TIM_CHANNEL_1) != HAL_OK)
{
Error_Handler();
}
sConfigIC.ICPolarity = TIM_INPUTCHANNELPOLARITY_FALLING;
sConfigIC.ICSelection = TIM_ICSELECTION_INDIRECTTI;
if (HAL_TIM_IC_ConfigChannel(&htim1, &sConfigIC, TIM_CHANNEL_2) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN TIM1_Init 2 */
/* USER CODE END TIM1_Init 2 */
}
/**
* @brief GPIO Initialization Function
* @param None
* @retval None
*/
static void MX_GPIO_Init(void)
{
GPIO_InitTypeDef GPIO_InitStruct = {0};
/* USER CODE BEGIN MX_GPIO_Init_1 */
/* USER CODE END MX_GPIO_Init_1 */
/* GPIO Ports Clock Enable */
__HAL_RCC_GPIOC_CLK_ENABLE();
__HAL_RCC_GPIOA_CLK_ENABLE();
/*Configure GPIO pin Output Level */
HAL_GPIO_WritePin(GPIOC, GPIO_PIN_13, GPIO_PIN_SET);
/*Configure GPIO pin Output Level */
HAL_GPIO_WritePin(GPIOA, GPIO_PIN_0, GPIO_PIN_RESET);
/*Configure GPIO pin : PC13 */
GPIO_InitStruct.Pin = GPIO_PIN_13;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_OD;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);
/*Configure GPIO pin : PA0 */
GPIO_InitStruct.Pin = GPIO_PIN_0;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);
/* USER CODE BEGIN MX_GPIO_Init_2 */
/* USER CODE END MX_GPIO_Init_2 */
}
/* 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 */
5、定时器从模式控制器
1.从模式控制器框图
2.如何使用从模式控制器
3.从模式控制器的模式
4、旋钮编码器实验
a.什么是旋钮编码器
所谓编码器就是电机用于测量角度和转速的。本次实验我们用到的编码器为EC11.
图中有五个引脚ABCDE，其中AB两个引脚是两个触电，D接电源E接地，当A、B触电与金属片接触时由于金属片接地所以A、B产生低电平，当触电与金属片相离时由于外接上拉电阻的存在为高电压，故当轮盘转动的时候出点A和触电B就会产生一个脉冲信号。
由于AB两个触电位置上有前后之分所以当金属片不同方向的旋转时也会产生不同的脉冲。
所以现在我们可以通过数脉冲的个数知道转动了多少度，比较AB的先后关系知道是顺时针还是逆时针转动。
b.旋钮编码器实现每转动一次计数值变化
1.打开STM32CUBEMX，新建工程，选用STM32F103C8T6作为核心板
2.时钟配置：
我们用定时器2作为编码器输入，在TIM2 Mode and Configuration的Mode设置里面将Combined Channels中选为Encoder Mode，然后在下面的Configuration中Prescaler设置为0，counter Period设置为10（表示最大计数为10）auto—reload preload设置为Enable，其他设置不变。
为什么这样配置，因为当我们选择为编码器模式后，通道CH1和CH2默认就连接到了旋转编码器的A、B触角，当旋钮转动后产生TI1FP1和TI2FP2直接给编码器接口提供一个时钟信号再将输入的值给到CNT进行计数.
3.编码器的三种模式
作者：几许_
