freeRtos信号量的使用

一.信号量的基本概念?

"give"给出资源，计数值加1；"take"获得资源，计数值减1?

二.创建信号量?

一开始的时候任务1计算，计算完之后信号量里面的计数值增加1，任务2获得信号量，但是任务2里面的计数值为0，就在里面阻塞，等任务1释放give信号量的时候，任务2被唤醒。

static int sum = 0;
static volatile int flagCalcEnd = 0;
static volatile int flagUARTused = 0;
static SemaphoreHandle_t xSemCalc;

void Task1Function(void * param)
{
	volatile int i = 0;
	while (1)
	{
		for (i = 0; i < 10000000; i++)
			sum++;
		//printf("1");
		xSemaphoreGive(xSemCalc);
		vTaskDelete(NULL);
	}
}

void Task2Function(void * param)
{
	while (1)
	{
		//if (flagCalcEnd)
		flagCalcEnd = 0;
		xSemaphoreTake(xSemCalc,portMAX_DELAY);
		flagCalcEnd = 1;
		printf("sum = %d\r\n", sum);
	}
}

void TaskGenericFunction(void * param)
{
	while (1)
	{
		if (!flagUARTused)
		{
			flagCalcEnd = 1;
			printf("%s\r\n", (char *)param);
			flagCalcEnd = 0;
			vTaskDelay(1);
		}
	}
}



/*-----------------------------------------------------------*/

int main( void )
{
	TaskHandle_t xHandleTask1;
		
#ifdef DEBUG
  debug();
#endif

	prvSetupHardware();

	printf("Hello, world!\r\n");

	xSemCalc=xSemaphoreCreateCounting(10,0);
	xTaskCreate(Task1Function, "Task1", 100, NULL, 1, &xHandleTask1);
	xTaskCreate(Task2Function, "Task2", 100, NULL, 1, NULL);

	//xTaskCreate(TaskGenericFunction, "Task3", 100, "Task 3 is running", 1, NULL);
	//xTaskCreate(TaskGenericFunction, "Task4", 100, "Task 4 is running", 1, NULL);

	/* Start the scheduler. */
	vTaskStartScheduler();

	/* Will only get here if there was not enough heap space to create the
	idle task. */
	return 0;
}

void TaskGenericFunction(void * param)
{
	while (1)
	{
		xSemaphoreTake(xSemUART,portMAX_DELAY);//获得信号量
		printf("%s\r\n", (char *)param);
		xSemaphoreGive(xSemUART);//释放信号量
		vTaskDelay(1);
	}
}



/*-----------------------------------------------------------*/

int main( void )
{
	TaskHandle_t xHandleTask1;
		
#ifdef DEBUG
  debug();
#endif

	prvSetupHardware();

	printf("Hello, world!\r\n");

	xSemCalc=xSemaphoreCreateCounting(10,0);
	xTaskCreate(Task1Function, "Task1", 100, NULL, 1, &xHandleTask1);
	xTaskCreate(Task2Function, "Task2", 100, NULL, 1, NULL);

	xSemUART=xSemaphoreCreateBinary();
	xSemaphoreGive(xSemUART);
	xTaskCreate(TaskGenericFunction, "Task3", 100, "Task 3 is running", 1, NULL);
	xTaskCreate(TaskGenericFunction, "Task4", 100, "Task 4 is running", 1, NULL);

	/* Start the scheduler. */
	vTaskStartScheduler();

	/* Will only get here if there was not enough heap space to create the
	idle task. */
	return 0;
}

三.give和take?

?