对于FreeRTOS中的操作，最常用的就是创建、删除、暂停和恢复任务。
此次实验目标：
1.创建任务一：LED1每间隔1秒闪烁一次，并通过串口打印
2.创建任务二：LED2每间隔0.5秒闪烁一次，并通过串口打印
3.创建任务三：通过KEY1实现对任务一的创建和删除。
按键按下以后如果有任务一就删除任务一，没有任务一就创建任务一。
4. 创建任务四：通过KEY2实现对任务二的暂停和恢复。
按键按下以后如果任务二在执行就暂停任务二，任务二在暂停就恢复任务二。
实现方式：
使用正点原子探索者，主控芯片为STM32F407ZGT6。
一、主要的电气原理图如下：
二、CubeMX配置
1.设置FreeRTOS
2.设置usart1
波特率115200
3.设置时钟，选择外部高速时钟
配置时钟树如下
4.注意一定要修改时基
5.生成代码
三、编写代码（都在freertos.c中写）
1.串口重定向
#include <stdio.h>// 包含标准输入输出头文件int fputc(int ch,FILE *f){//采用轮询方式发送1字节数据，超时时间设置为无限等待HAL_UART_Transmit(&huart1,(uint8_t *)&ch,1,HAL_MAX_DELAY);return ch;}int fgetc(FILE *f){uint8_t ch;// 采用轮询方式接收 1字节数据，超时时间设置为无限等待HAL_UART_Receive( &huart1,(uint8_t*)&ch,1, HAL_MAX_DELAY );return ch;}2.实现任务的代码
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 *//* 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 LED1 */osThreadDef(LED1, led1, osPriorityNormal, 0, 128);LED1Handle = osThreadCreate(osThread(LED1), NULL);/* definition and creation of LED2 */osThreadDef(LED2, led2, osPriorityIdle, 0, 128);LED2Handle = osThreadCreate(osThread(LED2), NULL);/* definition and creation of KEY1 */osThreadDef(KEY1, key1, osPriorityIdle, 0, 128);KEY1Handle = osThreadCreate(osThread(KEY1), NULL);/* definition and creation of KEY2 */osThreadDef(KEY2, key2, osPriorityIdle, 0, 128);KEY2Handle = osThreadCreate(osThread(KEY2), NULL);/* USER CODE BEGIN RTOS_THREADS *//* add threads, ... *//* USER CODE END RTOS_THREADS */}/* USER CODE BEGIN Header_led1 *//*** @brief Function implementing the LED1 thread.* @param argument: Not used* @retval None*//* USER CODE END Header_led1 */void led1(void const * argument){/* USER CODE BEGIN led1 *//* Infinite loop */for(;;){printf("led1\n\r");HAL_GPIO_TogglePin(GPIOF,GPIO_PIN_9);osDelay(1000);}/* USER CODE END led1 */}/* USER CODE BEGIN Header_led2 *//*** @brief Function implementing the LED2 thread.* @param argument: Not used* @retval None*//* USER CODE END Header_led2 */void led2(void const * argument){/* USER CODE BEGIN led2 *//* Infinite loop */for(;;){printf("led2\n\r");HAL_GPIO_TogglePin(GPIOF,GPIO_PIN_10);osDelay(500);}/* USER CODE END led2 */}/* USER CODE BEGIN Header_key1 *//*** @brief Function implementing the KEY1 thread.* @param argument: Not used* @retval None*//* USER CODE END Header_key1 */void key1(void const * argument){/* USER CODE BEGIN key1 *//* Infinite loop */for(;;){if(HAL_GPIO_ReadPin(GPIOE,GPIO_PIN_4)==0){osDelay(20);//防误触if(LED1Handle==NULL){printf("key1==creat\n\r");osThreadDef(LED1, led1, osPriorityNormal, 0, 128);LED1Handle = osThreadCreate(osThread(LED1), (void*)"new task1");}else{vTaskDelete(LED1Handle);LED1Handle=NULL;printf("key1==delete\n\r");}}}/* USER CODE END key1 */}/* USER CODE BEGIN Header_key2 *//*** @brief Function implementing the KEY2 thread.* @param argument: Not used* @retval None*//* USER CODE END Header_key2 */void key2(void const * argument){/* USER CODE BEGIN key2 */char Flag=0;/* Infinite loop */for(;;){if(HAL_GPIO_ReadPin(GPIOE,GPIO_PIN_3)==0){osDelay(20);//防误触if(Flag==0){printf("key2 suspend\n\r");vTaskSuspend(LED2Handle);Flag=1;}else{vTaskResume(LED2Handle);printf("key2 resume \n\r");Flag=0;}}}/* USER CODE END key2 */}/* Private application code --------------------------------------------------*/注意：任务被删除时，句柄不会删除，需要手动清空。
