一、消息队列（queue）
队列是一种用于实现任务与任务之间，任务与中断之间消息交流的机制。
注意：1.数据的操作是FIFO模式。
2.队列需要明确数据的大小和队列的长度。
3.写和读都会出现堵塞。
实验：创建一个消息队列，两个发送任务，一个接收任务。
其中任务一任务三的等待时间为0，任务二的等待时间为portMAX_DELAY（死等）。
实现：在前一个项目的基础上进行更改【STM32】利用CubeMX对FreeRTOS用按键控制任务
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 *//* Create the semaphores(s) *//* 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 *//* Create the queue(s) *//* definition and creation of myQueue01 */osMessageQDef(myQueue01, 2, uint32_t);myQueue01Handle = osMessageCreate(osMessageQ(myQueue01), NULL);/* USER CODE BEGIN RTOS_QUEUES *//* add queues, ... *//* USER CODE END RTOS_QUEUES *//* Create the thread(s) *//* definition and creation of Task1 */osThreadDef(Task1, StartDefaultTask, osPriorityNormal, 0, 128);Task1Handle = osThreadCreate(osThread(Task1), NULL);/* definition and creation of Task2 */osThreadDef(Task2, StartTask02, osPriorityIdle, 0, 128);Task2Handle = osThreadCreate(osThread(Task2), NULL);/* definition and creation of Task3 */osThreadDef(Task3, StartTask03, osPriorityIdle, 0, 128);Task3Handle = osThreadCreate(osThread(Task3), NULL);/* USER CODE BEGIN RTOS_THREADS *//* add threads, ... *//* USER CODE END RTOS_THREADS */}/* USER CODE BEGIN Header_StartDefaultTask *//*** @brief Function implementing the Task1 thread.* @param argument: Not used* @retval None*//* USER CODE END Header_StartDefaultTask */void StartDefaultTask(void const * argument){/* USER CODE BEGIN StartDefaultTask *//* Infinite loop */BaseType_t xStatus;uint32_t Buf=10086;for(;;){if(HAL_GPIO_ReadPin(GPIOE,GPIO_PIN_3)==0){osDelay(20);if(HAL_GPIO_ReadPin(GPIOE,GPIO_PIN_3)==0){xStatus=xQueueSendToBack(myQueue01Handle,&Buf,0);if(xStatus!=pdTRUE){printf("NO1\r\n");osDelay(500);}else{printf("YES1%u\r\n",Buf);osDelay(500);}}}}/* USER CODE END StartDefaultTask */}/* USER CODE BEGIN Header_StartTask02 *//*** @brief Function implementing the Task2 thread.* @param argument: Not used* @retval None*//* USER CODE END Header_StartTask02 */void StartTask02(void const * argument){/* USER CODE BEGIN StartTask02 *//* Infinite loop */BaseType_t xStatus;uint32_t Buf=66666;for(;;){if(HAL_GPIO_ReadPin(GPIOE,GPIO_PIN_4)==0){osDelay(20);if(HAL_GPIO_ReadPin(GPIOE,GPIO_PIN_4)==0){xStatus=xQueueSendToBack(myQueue01Handle,&Buf,portMAX_DELAY);if(xStatus!=pdTRUE){printf("NO2\r\n");osDelay(500);}else{printf("YES2%u\r\n",Buf);osDelay(500);}}}}/* USER CODE END StartTask02 */}/* USER CODE BEGIN Header_StartTask03 *//*** @brief Function implementing the Task3 thread.* @param argument: Not used* @retval None*//* USER CODE END Header_StartTask03 */void StartTask03(void const * argument){/* USER CODE BEGIN StartTask03 *//* Infinite loop *///BaseType_t xStatus;uint32_t Buf=0;for(;;){if(HAL_GPIO_ReadPin(GPIOE,GPIO_PIN_2)==0){osDelay(20);if(HAL_GPIO_ReadPin(GPIOE,GPIO_PIN_2)==0){printf("当前%u\r\n",Buf);//xStatus=xQueueReceive(myQueue01Handle,&Buf,portMAX_DELAY);if(xQueueReceive(myQueue01Handle,&Buf,portMAX_DELAY)!=pdTRUE){printf("NO3\r\n");}else{printf("YES3%u\r\n",Buf);}}}}/* USER CODE END StartTask03 */}现象：队列满了以后，任务一无法发送，任务二会死等，队列空闲以后完成发送。
二、信号量
消息队列用于传输多个数据，占用时间也相对较长，但有时只需要传输状态，因此引入信号量。信号量也是队列的一种。信号量有两种，如果它的量只有0（被拿走的状态）和1（被填入的状态）两种状态，就称为二进制的信号量；当量的状态大于两种，就称为计数型信号量。
1.二值信号量
实验：任务一：按键采集数据；任务二：拿走以后串口发送信息
实现：
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 *//* Create the semaphores(s) *//* definition and creation of myBinarySem01 */osSemaphoreDef(myBinarySem01);myBinarySem01Handle = osSemaphoreCreate(osSemaphore(myBinarySem01), 1);/* 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 *//* Create the queue(s) *//* definition and creation of myQueue01 */osMessageQDef(myQueue01, 2, uint32_t);myQueue01Handle = osMessageCreate(osMessageQ(myQueue01), NULL);/* USER CODE BEGIN RTOS_QUEUES *//* add queues, ... *//* USER CODE END RTOS_QUEUES *//* Create the thread(s) *//* definition and creation of Task1 */osThreadDef(Task1, StartDefaultTask, osPriorityNormal, 0, 128);Task1Handle = osThreadCreate(osThread(Task1), NULL);/* definition and creation of Task2 */osThreadDef(Task2, StartTask02, osPriorityNormal, 0, 128);Task2Handle = osThreadCreate(osThread(Task2), NULL);/* definition and creation of Task3 */osThreadDef(Task3, StartTask03, osPriorityNormal, 0, 128);Task3Handle = osThreadCreate(osThread(Task3), NULL);/* USER CODE BEGIN RTOS_THREADS *//* add threads, ... *//* USER CODE END RTOS_THREADS */}/* USER CODE BEGIN Header_StartDefaultTask *//*** @brief Function implementing the Task1 thread.* @param argument: Not used* @retval None*//* USER CODE END Header_StartDefaultTask */void StartDefaultTask(void const * argument){/* USER CODE BEGIN StartDefaultTask *//* Infinite loop */BaseType_t xStatus;uint32_t Buf=10086;for(;;){// {if(HAL_GPIO_ReadPin(GPIOE,GPIO_PIN_3)==0){osDelay(20);if(HAL_GPIO_ReadPin(GPIOE,GPIO_PIN_3)==0){//xStatus=xQueueSendToBack(myQueue01Handle,&Buf,0);if(xSemaphoreGive(myBinarySem01Handle)==pdTRUE){printf("NO1\r\n");}else{printf("YES1%u\r\n",Buf);}}}}/* USER CODE END StartDefaultTask */}/* USER CODE BEGIN Header_StartTask03 *//*** @brief Function implementing the Task3 thread.* @param argument: Not used* @retval None*//* USER CODE END Header_StartTask03 */void StartTask03(void const * argument){/* USER CODE BEGIN StartTask03 *//* Infinite loop */uint32_t Buf=0;for(;;){if(HAL_GPIO_ReadPin(GPIOE,GPIO_PIN_2)==0){osDelay(20);if(HAL_GPIO_ReadPin(GPIOE,GPIO_PIN_2)==0){if(xSemaphoreTake(myBinarySem01Handle,0)==pdTRUE){printf("YES3\r\n");}else{printf("NO3%u\r\n",Buf);}}}}/* USER CODE END StartTask03 */}现象：当按键释放了信号量，串口才能成功发送信息。
2.记数型信号量
实验：任务一 ：按键一记录人进来；按键二记录人出去；（最多有10个人）
任务二：串口每隔3S打印人数。
实现：
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 *//* Create the semaphores(s) *//* definition and creation of myBinarySem01 */osSemaphoreDef(myBinarySem01);myBinarySem01Handle = osSemaphoreCreate(osSemaphore(myBinarySem01), 1);/* definition and creation of myCountingSem01 */osSemaphoreDef(myCountingSem01);myCountingSem01Handle = osSemaphoreCreate(osSemaphore(myCountingSem01), 10);/* 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 *//* Create the queue(s) *//* definition and creation of myQueue01 */osMessageQDef(myQueue01, 2, uint32_t);myQueue01Handle = osMessageCreate(osMessageQ(myQueue01), NULL);/* USER CODE BEGIN RTOS_QUEUES *//* add queues, ... *//* USER CODE END RTOS_QUEUES *//* Create the thread(s) *//* definition and creation of Task1 */osThreadDef(Task1, StartDefaultTask, osPriorityNormal, 0, 128);Task1Handle = osThreadCreate(osThread(Task1), NULL);/* definition and creation of Task2 */osThreadDef(Task2, StartTask02, osPriorityNormal, 0, 128);Task2Handle = osThreadCreate(osThread(Task2), NULL);/* definition and creation of Task3 */osThreadDef(Task3, StartTask03, osPriorityNormal, 0, 128);Task3Handle = osThreadCreate(osThread(Task3), NULL);/* USER CODE BEGIN RTOS_THREADS *//* add threads, ... *//* USER CODE END RTOS_THREADS */}/* USER CODE BEGIN Header_StartDefaultTask *//*** @brief Function implementing the Task1 thread.* @param argument: Not used* @retval None*//* USER CODE END Header_StartDefaultTask */void StartDefaultTask(void const * argument){/* USER CODE BEGIN StartDefaultTask *//* Infinite loop */for(;;){if(HAL_GPIO_ReadPin(GPIOE,GPIO_PIN_3)==0){osDelay(20);if(HAL_GPIO_ReadPin(GPIOE,GPIO_PIN_3)==0){if(xSemaphoreGive(myCountingSem01Handle)!=pdTRUE){printf("NO1\r\n");}else{printf("YES1\r\n");}}}if(HAL_GPIO_ReadPin(GPIOE,GPIO_PIN_4)==0){osDelay(20);if(HAL_GPIO_ReadPin(GPIOE,GPIO_PIN_4)==0){if(xSemaphoreTake(myCountingSem01Handle,0)!=pdTRUE){printf("NO2\r\n");}else{printf("YES2\r\n");}}}}/* USER CODE END StartDefaultTask */}/* USER CODE BEGIN Header_StartTask02 *//*** @brief Function implementing the Task2 thread.* @param argument: Not used* @retval None*//* USER CODE END Header_StartTask02 */void StartTask02(void const * argument){/* USER CODE BEGIN StartTask02 *//* Infinite loop */for(;;){}/* USER CODE END StartTask02 */}/* USER CODE BEGIN Header_StartTask03 *//*** @brief Function implementing the Task3 thread.* @param argument: Not used* @retval None*//* USER CODE END Header_StartTask03 */void StartTask03(void const * argument){/* USER CODE BEGIN StartTask03 *//* Infinite loop */for(;;){printf("possess %d people\r\n",(uint16_t)uxSemaphoreGetCount(myCountingSem01Handle));osDelay(3000);}/* USER CODE END StartTask03 */}因为用了函数
myCountingSem01Handle = osSemaphoreCreate(osSemaphore(myCountingSem01), 10);默认当前计数值为满值。如果设置为0，使用下面的函数：
myCountingSem01Handle=xSemaphoreCreateCounting(10,0);现象：通过按键一和二实现记录人数，并串口打印了当前人数。
