1. Creating and using a task

Amruta (talk) 13:44, 8 April 2015 (IST)

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Intro

This is our first tutorial with FreeRTOS so start with a simple example of how to create and use a task.

Before going to this tutorial its recommended to first go through the FreeRTOS basics tutorial.

1. In main function we will create 3 tasks viz., MyTask1, MyTask2 and MyTask3 with priorities 1,2 and 3 respectively.
2. An idle task is also created, which will be run when there are no tasks in RUN state.
3. Only creating task is not sufficient. Tasks will be executed only when the scheduler is started.

So call vTaskStartScheduler() to start the scheduler.

Code

For making it easier to understand what is happening, we are displaying some data on UART.

You can find the function prototypes and details here.

	/***************************************************************************************************
	ExploreEmbedded
	****************************************************************************************************
	* File: main.c (ARM controllers FreeRTOS)
	* Version: 15.0
	* Author: ExploreEmbedded
	* Website: http://www.exploreembedded.com/wiki
	* Description: Program to demonstrate the creating and using a task in FreeRTOS
	The libraries have been tested on ExploreEmbedded development boards. We strongly believe that the
	library works on any of development boards for respective controllers. However, ExploreEmbedded
	disclaims any kind of hardware failure resulting out of usage of libraries, directly or indirectly.
	Files may be subject to change without prior notice. The revision history contains the information
	related to updates.
	GNU GENERAL PUBLIC LICENSE:
	This program is free software: you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation, either version 3 of the License, or
	(at your option) any later version.
	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	GNU General Public License for more details.
	You should have received a copy of the GNU General Public License
	along with this program. If not, see <http://www.gnu.org/licenses/>.
	Errors and omissions should be reported to codelibraries@exploreembedded.com
	**************************************************************************************************/
	/* Scheduler include files. */
	#include "FreeRtOSConfig.h"
	#include "FreeRTOS.h"
	#include "task.h"
	#include "croutine.h"
	#include "uart.h" // Explore Emnedded UART library
	/* Local Tasks declaration */
	static void MyTask1(void* pvParameters);
	static void MyTask2(void* pvParameters);
	static void MyTask3(void* pvParameters);
	static void MyIdleTask(void* pvParameters);
	int main(void)
	{
	SystemInit(); /* Initialize the microcontroller system */
	UART_Init(38400); /* Initialize the Uart module */
	/* Create the three tasks with priorities 1,2,3. Only tasks will be created.
	* Tasks will be excecuted once the scheduler is started.
	* An idle task is also created, which will be run when there are no tasks in RUN state */
	xTaskCreate( MyTask1, ( signed char * )"Task1", configMINIMAL_STACK_SIZE, NULL, 1, NULL );
	xTaskCreate( MyTask2, ( signed char * )"Task2", configMINIMAL_STACK_SIZE, NULL, 2, NULL );
	xTaskCreate( MyTask3, ( signed char * )"Task3", configMINIMAL_STACK_SIZE, NULL, 3, NULL );
	xTaskCreate( MyIdleTask, ( signed char * )"IdleTask", configMINIMAL_STACK_SIZE, NULL, tskIDLE_PRIORITY, NULL );
	UART_Printf("\n\rIn the main");
	vTaskStartScheduler(); /* Start the schedular */
	while(1);
	}
	/* Task1 with priority 1 */
	static void MyTask1(void* pvParameters)
	{
	while(1)
	{
	UART_Printf("\n\rTask1");
	vTaskDelay(100);
	}
	}
	/* Task1 with priority 2 */
	static void MyTask2(void* pvParameters)
	{
	while(1)
	{
	UART_Printf("\n\rTask2");
	vTaskDelay(250);
	}
	}
	/* Task1 with priority 3 */
	static void MyTask3(void* pvParameters)
	{
	while(1)
	{
	UART_Printf("\n\rTask3");
	vTaskDelay(600);
	}
	}
	static void MyIdleTask(void* pvParameters)
	{
	while(1)
	{
	UART_Printf("\n\rIn idle state");
	}
	}

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