FreeRTOS——软件定时器

一、什么是定时器

简单可以理解为闹钟，到达指定一段时间后，就会响铃。

STM32 芯片自带硬件定时器，精度较高，达到定时时间后会触发中断，也可以生成 PWM 、输入捕获、输出比较，等等，功能强大，但是由于硬件的限制，个数有限。

软件定时器也可以实现定时功能，达到定时时间后可调用回调函数，可以在回调函数里处理信息。

二、软件定时器优缺点

优点：

1. 简单、成本低；

2. 只要内存足够，可创建多个；

缺点：

精度较低，容易受中断影响。在大多数情况下够用，但对于精度要求比较高的场合不建议使用。

三、软件定时器原理

定时器是一个可选的、不属于 FreeRTOS 内核的功能，它是由定时器服务任务来提供的。

在调用函数 vTaskStartScheduler() 开启任务调度器的时候，会创建一个用于管理软件定时器的任务，这个任务就叫做软件定时器服务任务。

1. 负责软件定时器超时的逻辑判断

2. 调用超时软件定时器的超时回调函数

3. 处理软件定时器命令队列

FreeRTOS提供了很多定时器有关的API函数，这些API函数大多都使用FreeRTOS的队列发送命令给定时器服务任务。这个队列叫做定时器命令队列。定时器命令队列是提供给FreeRTOS的软件定时器使用的，用户不能直接访问！

四、软件定时器相关配置

软件定时器有一个定时器服务任务和定时器命令队列，这两个东西肯定是要配置的，相关的配置也是放到文件FreeRTOSConfig.h中的，涉及到的配置如下：

1、configUSE_TIMERS

如果要使用软件定时器的话宏configUSE_TIMERS一定要设置为1，当设置为1的话定时器服务任务就会在启动FreeRTOS调度器的时候自动创建。

2、configTIMER_TASK_PRIORITY

设置软件定时器服务任务的任务优先级，可以为0~(configMAX_PRIORITIES-1)。优先级一定要根据实际的应用要求来设置。如果定时器服务任务的优先级设置的高的话，定时器命令队列中的命令和定时器回调函数就会及时的得到处理。

3、configTIMER_QUEUE_LENGTH

此宏用来设置定时器命令队列的队列长度。

4、configTIMER_TASK_STACK_DEPTH

此宏用来设置定时器服务任务的任务堆栈大小。

五、单次定时器和周期定时器

单次定时器： 只超时一次，调用一次回调函数。可手动再开启定时器；

周期定时器： 多次超时，多次调用回调函数。

六、软件定时器相关 API 函数

6.1、创建软件定时器

TimerHandle_t xTimerCreate( const char * const          pcTimerName,const TickType_t            xTimerPeriod,const UBaseType_t           uxAutoReload,void * const                pvTimerID,TimerCallbackFunction_t     pxCallbackFunction 
);

参数：

pcTimerName：软件定时器名称

xTimerPeriodInTicks：定时超时时间，单位：系统时钟节拍。宏 pdMS_TO_TICKS() 可用于将以毫秒为单位指定的时间转换为以 tick 为单位指定的时间。

uxAutoReload：定时器模式， pdTRUE：周期定时器， pdFALSE：单次定时器

pvTimerID：软件定时器 ID，用于多个软件定时器公用一个超时回调函数

pxCallbackFunction：软件定时器超时回调函数

返回值：成功：定时器句柄失败：NULL

6.2、开启软件定时器

BaseType_t xTimerStart( TimerHandle_t    xTimer,TickType_t       xBlockTime 
);

参数：

xTimer：待开启的软件定时器的句柄

xTickToWait：发送命令到软件定时器命令队列的最大等待时间

返回值：

pdPASS：开启成功 pdFAIL：开启失败

6.3、停止软件定时器

BaseType_t xTimerStop( TimerHandle_t  xTimer,TickType_t     xBlockTime 
);

参数与返回值同上。

6.4、复位软件定时器

BaseType_t xTimerReset( TimerHandle_t  xTimer,TickType_t     xBlockTime 
);

参数与返回值同上。

该功能将使软件定时器的重新开启定时，复位后的软件定时器以复位时的时刻作为开启时刻重新定时。

6.5、更改软件定时器定时时间

BaseType_t xTimerChangePeriod( TimerHandle_t  xTimer,TickType_t     xNewPeriod,TickType_t     xBlockTime 
);

xNewPeriod：新的定时超时时间，单位：系统时钟节拍。

其余参数与返回值同上。

七、实操

7.1、任务需求

创建两个定时器：

定时器1，周期定时器，每1秒打印一次 I LOVE YOU

定时器2，单次定时器，启动后 2 秒打印一次 You Look Handsome

7.2、代码

7.2.1、CubeMX封装函数代码

/* USER CODE BEGIN Header */
/********************************************************************************* File Name          : freertos.c* Description        : Code for freertos applications******************************************************************************* @attention** Copyright (c) 2024 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 "FreeRTOS.h"
#include "task.h"
#include "main.h"
#include "cmsis_os.h"/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "stdio.h"
/* 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 Variables *//* USER CODE END Variables */
osThreadId defaultTaskHandle;
osTimerId myTimer01Handle;				/*定时器1句柄*/
osTimerId myTimer02Handle;/* Private function prototypes -----------------------------------------------*/
/* USER CODE BEGIN FunctionPrototypes *//* USER CODE END FunctionPrototypes */void StartDefaultTask(void const * argument);
void Callback01(void const * argument);
void Callback02(void const * argument);void MX_FREERTOS_Init(void); /* (MISRA C 2004 rule 8.1) *//* GetIdleTaskMemory prototype (linked to static allocation support) */
void vApplicationGetIdleTaskMemory( StaticTask_t **ppxIdleTaskTCBBuffer, StackType_t **ppxIdleTaskStackBuffer, uint32_t *pulIdleTaskStackSize );/* GetTimerTaskMemory prototype (linked to static allocation support) */
void vApplicationGetTimerTaskMemory( StaticTask_t **ppxTimerTaskTCBBuffer, StackType_t **ppxTimerTaskStackBuffer, uint32_t *pulTimerTaskStackSize );/* USER CODE BEGIN GET_IDLE_TASK_MEMORY */
static StaticTask_t xIdleTaskTCBBuffer;
static StackType_t xIdleStack[configMINIMAL_STACK_SIZE];void vApplicationGetIdleTaskMemory( StaticTask_t **ppxIdleTaskTCBBuffer, StackType_t **ppxIdleTaskStackBuffer, uint32_t *pulIdleTaskStackSize )
{*ppxIdleTaskTCBBuffer = &xIdleTaskTCBBuffer;*ppxIdleTaskStackBuffer = &xIdleStack[0];*pulIdleTaskStackSize = configMINIMAL_STACK_SIZE;/* place for user code */
}
/* USER CODE END GET_IDLE_TASK_MEMORY *//* USER CODE BEGIN GET_TIMER_TASK_MEMORY */
static StaticTask_t xTimerTaskTCBBuffer;
static StackType_t xTimerStack[configTIMER_TASK_STACK_DEPTH];void vApplicationGetTimerTaskMemory( StaticTask_t **ppxTimerTaskTCBBuffer, StackType_t **ppxTimerTaskStackBuffer, uint32_t *pulTimerTaskStackSize )
{*ppxTimerTaskTCBBuffer = &xTimerTaskTCBBuffer;*ppxTimerTaskStackBuffer = &xTimerStack[0];*pulTimerTaskStackSize = configTIMER_TASK_STACK_DEPTH;/* place for user code */
}
/* USER CODE END GET_TIMER_TASK_MEMORY *//*** @brief  FreeRTOS initialization* @param  None* @retval None*/
void MX_FREERTOS_Init(void) {/* USER CODE BEGIN Init *//* USER CODE END Init *//* USER CODE BEGIN RTOS_MUTEX *//* add mutexes, ... *//* USER CODE END RTOS_MUTEX *//* USER CODE BEGIN RTOS_SEMAPHORES *//* add semaphores, ... *//* USER CODE END RTOS_SEMAPHORES *//* Create the timer(s) *//* definition and creation of myTimer01 */osTimerDef(myTimer01, Callback01);myTimer01Handle = osTimerCreate(osTimer(myTimer01), osTimerPeriodic, NULL);		/*创建软件定时器1，osTimerCreate是CubeMX封装函数，底层还是xTimerCreate*//* definition and creation of myTimer02 */osTimerDef(myTimer02, Callback02);myTimer02Handle = osTimerCreate(osTimer(myTimer02), osTimerOnce, NULL);/* USER CODE BEGIN RTOS_TIMERS *//* start timers, add new ones, ... *//* USER CODE END RTOS_TIMERS *//* USER CODE BEGIN RTOS_QUEUES *//* add queues, ... *//* USER CODE END RTOS_QUEUES *//* Create the thread(s) *//* definition and creation of defaultTask */osThreadDef(defaultTask, StartDefaultTask, osPriorityNormal, 0, 128);defaultTaskHandle = osThreadCreate(osThread(defaultTask), NULL);/* USER CODE BEGIN RTOS_THREADS *//* add threads, ... *//* USER CODE END RTOS_THREADS */}/* USER CODE BEGIN Header_StartDefaultTask */
/*** @brief  Function implementing the defaultTask thread.* @param  argument: Not used* @retval None*/
/* USER CODE END Header_StartDefaultTask */
void StartDefaultTask(void const * argument)
{/* USER CODE BEGIN StartDefaultTask */osTimerStart(myTimer01Handle, 1000);			/*开启软件定时器1，定时1000ms*/
// xTimerChangePeriod(myTimer01Handle, pdMS_TO_TICKS(1000), 0);			/*修改软件定时器1的事件为1000ms*/osTimerStart(myTimer02Handle, 2000);/* Infinite loop */for(;;){osDelay(1);}/* USER CODE END StartDefaultTask */
}/* Callback01 function */
void Callback01(void const * argument)	/*定时器1对应的回调函数*/
{/* USER CODE BEGIN Callback01 */printf("周期定时器：I LOVE YOU!\r\n");/* USER CODE END Callback01 */
}/* Callback02 function */
void Callback02(void const * argument)
{/* USER CODE BEGIN Callback02 */printf("单次定时器：You Look Handsome!\r\n");/* USER CODE END Callback02 */
}/* Private application code --------------------------------------------------*/
/* USER CODE BEGIN Application *//* USER CODE END Application */

7.2.1、原函数代码

/* USER CODE BEGIN Header */
/********************************************************************************* File Name          : freertos.c* Description        : Code for freertos applications******************************************************************************* @attention** Copyright (c) 2024 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 "FreeRTOS.h"
#include "task.h"
#include "main.h"
#include "cmsis_os.h"/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "stdio.h"
/* 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 Variables *//* USER CODE END Variables */
osThreadId defaultTaskHandle;
osTimerId myTimer01Handle;				/*定时器1句柄*/
osTimerId myTimer02Handle;/* Private function prototypes -----------------------------------------------*/
/* USER CODE BEGIN FunctionPrototypes *//* USER CODE END FunctionPrototypes */void StartDefaultTask(void const * argument);
void Callback01(void const * argument);
void Callback02(void const * argument);void MX_FREERTOS_Init(void); /* (MISRA C 2004 rule 8.1) *//* GetIdleTaskMemory prototype (linked to static allocation support) */
void vApplicationGetIdleTaskMemory( StaticTask_t **ppxIdleTaskTCBBuffer, StackType_t **ppxIdleTaskStackBuffer, uint32_t *pulIdleTaskStackSize );/* GetTimerTaskMemory prototype (linked to static allocation support) */
void vApplicationGetTimerTaskMemory( StaticTask_t **ppxTimerTaskTCBBuffer, StackType_t **ppxTimerTaskStackBuffer, uint32_t *pulTimerTaskStackSize );/* USER CODE BEGIN GET_IDLE_TASK_MEMORY */
static StaticTask_t xIdleTaskTCBBuffer;
static StackType_t xIdleStack[configMINIMAL_STACK_SIZE];void vApplicationGetIdleTaskMemory( StaticTask_t **ppxIdleTaskTCBBuffer, StackType_t **ppxIdleTaskStackBuffer, uint32_t *pulIdleTaskStackSize )
{*ppxIdleTaskTCBBuffer = &xIdleTaskTCBBuffer;*ppxIdleTaskStackBuffer = &xIdleStack[0];*pulIdleTaskStackSize = configMINIMAL_STACK_SIZE;/* place for user code */
}
/* USER CODE END GET_IDLE_TASK_MEMORY *//* USER CODE BEGIN GET_TIMER_TASK_MEMORY */
static StaticTask_t xTimerTaskTCBBuffer;
static StackType_t xTimerStack[configTIMER_TASK_STACK_DEPTH];void vApplicationGetTimerTaskMemory( StaticTask_t **ppxTimerTaskTCBBuffer, StackType_t **ppxTimerTaskStackBuffer, uint32_t *pulTimerTaskStackSize )
{*ppxTimerTaskTCBBuffer = &xTimerTaskTCBBuffer;*ppxTimerTaskStackBuffer = &xTimerStack[0];*pulTimerTaskStackSize = configTIMER_TASK_STACK_DEPTH;/* place for user code */
}
/* USER CODE END GET_TIMER_TASK_MEMORY *//*** @brief  FreeRTOS initialization* @param  None* @retval None*/
void MX_FREERTOS_Init(void) {/* USER CODE BEGIN Init *//* USER CODE END Init *//* USER CODE BEGIN RTOS_MUTEX *//* add mutexes, ... *//* USER CODE END RTOS_MUTEX *//* USER CODE BEGIN RTOS_SEMAPHORES *//* add semaphores, ... *//* USER CODE END RTOS_SEMAPHORES *//* Create the timer(s) *//* definition and creation of myTimer01 */int Timer1_ID = 1;
//  osTimerDef(myTimer01, Callback01);
//  myTimer01Handle = osTimerCreate(osTimer(myTimer01), osTimerPeriodic, NULL);		/*创建软件定时器1，osTimerCreate是CubeMX封装函数，底层还是xTimerCreate*//*	创建软件定时器1,名称：myTimer01 ，定时时间1000ms：pdMS_TO_TICKS(1000)	，模式：周期定时*/myTimer01Handle = xTimerCreate("myTimer01" , pdMS_TO_TICKS(1000) ,pdTRUE , &Timer1_ID ,Callback01);/* definition and creation of myTimer02 */int Timer2_ID = 2;
//  osTimerDef(myTimer02, Callback02);
//  myTimer02Handle = osTimerCreate(osTimer(myTimer02), osTimerOnce, NULL);myTimer02Handle = xTimerCreate("myTimer02" , pdMS_TO_TICKS(2000) ,pdFALSE , &Timer2_ID ,Callback02);/* USER CODE BEGIN RTOS_TIMERS *//* start timers, add new ones, ... *//* USER CODE END RTOS_TIMERS *//* USER CODE BEGIN RTOS_QUEUES *//* add queues, ... *//* USER CODE END RTOS_QUEUES *//* Create the thread(s) *//* definition and creation of defaultTask */osThreadDef(defaultTask, StartDefaultTask, osPriorityNormal, 0, 128);defaultTaskHandle = osThreadCreate(osThread(defaultTask), NULL);/* USER CODE BEGIN RTOS_THREADS *//* add threads, ... *//* USER CODE END RTOS_THREADS */}/* USER CODE BEGIN Header_StartDefaultTask */
/*** @brief  Function implementing the defaultTask thread.* @param  argument: Not used* @retval None*/
/* USER CODE END Header_StartDefaultTask */
void StartDefaultTask(void const * argument)
{/* USER CODE BEGIN StartDefaultTask *///osTimerStart(myTimer01Handle, 1000);			/*CubeMX封装的函数，开启软件定时器1，定时1000ms*/
// xTimerChangePeriod(myTimer01Handle, pdMS_TO_TICKS(1000), 0);			/*修改软件定时器1的事件为1000ms*///osTimerStart(myTimer02Handle, 2000);xTimerStart(myTimer01Handle ,portMAX_DELAY);		/*开启定时器1*/xTimerStart(myTimer02Handle ,portMAX_DELAY);		/*开启定时器2*//* Infinite loop */for(;;){osDelay(1);}/* USER CODE END StartDefaultTask */
}/* Callback01 function */
void Callback01(void const * argument)	/*定时器1对应的回调函数*/
{/* USER CODE BEGIN Callback01 */printf("周期定时器：I LOVE YOU!\r\n");/* USER CODE END Callback01 */
}/* Callback02 function */
void Callback02(void const * argument)
{/* USER CODE BEGIN Callback02 */printf("单次定时器：You Look Handsome!\r\n");/* USER CODE END Callback02 */
}/* Private application code --------------------------------------------------*/
/* USER CODE BEGIN Application *//* USER CODE END Application */

结果：