In earlier tutorials, we saw how to create in the init and use it.
In this tutorial, we will see how to create a task from other tasks.
API Details
Here we will discuss some of the most frequently used APIs related to tasks.
xTaskCreate(): This interface is used to create a new Task, if the task is successfully created then it returns pdPass(1) or else errCOULD_NOT_ALLOCATE_REQUIRED_MEMORY(-1). Check this link for more details.
vTaskDelay(): This function is used to delay/block the task for specified delay time(ticks). INCLUDE_vTaskDelay needs to be set to 1 in FreeRtosConfig.h file for using this function. Check this link for more details.
vTaskDelete():This function is used to delete as task. We need to pass the taskHandle of the task to be deleted.
To delete the own task we should pass NULL as parameter.
Please check this link for detials.
vTaskPrioritySet(): This function is used to change/Set the priority of a task.
For this we need to pass the handle of the task and new priority to vTaskPrioritySet() function.
Check this link for more details.
vTaskPriorityGet(): This function is used to get the priority of a task.
For this we need to pass the handle of the task and it will return the task.
Check this link for more details.
Example
| /*************************************************************************************************** | |
| ExploreEmbedded Copyright Notice | |
| **************************************************************************************************** | |
| * File: 05-TaskPriorityChange | |
| * Version: 15.0 | |
| * Author: ExploreEmbedded | |
| * Website: http://www.exploreembedded.com/wiki | |
| * Description: File contains the free rtos example to demonstarte task priority change. | |
| This code has been developed and tested on ExploreEmbedded boards. | |
| We strongly believe that the library works on any of development boards for respective controllers. | |
| Check this link http://www.exploreembedded.com/wiki for awesome tutorials on 8051,PIC,AVR,ARM,Robotics,RTOS,IOT. | |
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| buying the ExploreEmbedded boards. | |
| The ExploreEmbedded libraries and examples are licensed under the terms of the new-bsd license(two-clause bsd license). | |
| See also: http://www.opensource.org/licenses/bsd-license.php | |
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| and that both those copyright notices and this permission notice appear in supporting documentation. | |
| **************************************************************************************************/ | |
| #include <Arduino_FreeRTOS.h> | |
| TaskHandle_t TaskHandle_1; | |
| TaskHandle_t TaskHandle_2; | |
| TaskHandle_t TaskHandle_4; | |
| void setup() | |
| { | |
| Serial.begin(9600); | |
| Serial.println(F("In Setup function")); | |
| /* Create three tasks with priorities 1,2 and 3. Capture the Task details to respective handlers */ | |
| xTaskCreate(MyTask1, "Task1", 120, NULL, 1, &TaskHandle_1); | |
| } | |
| void loop() | |
| { | |
| // put your main code here, to run repeatedly: | |
| Serial.println(F("Loop function")); | |
| delay(50); | |
| } | |
| /* Task1 with priority 1 */ | |
| static void MyTask1(void* pvParameters) | |
| { | |
| while(1) | |
| { | |
| Serial.print(F("Task1 with Priority:")); | |
| Serial.print(uxTaskPriorityGet(TaskHandle_1)); | |
| Serial.println(F(" Creating Task2")); | |
| xTaskCreate(MyTask2, "Task2", 100, NULL, 3, &TaskHandle_2); | |
| Serial.print(F("Task1 with Priority:")); | |
| Serial.print(uxTaskPriorityGet(TaskHandle_1)); | |
| Serial.println(F(" Deleting All")); | |
| vTaskDelete(TaskHandle_2); // Delete task2 and task4 using their handles | |
| vTaskDelete(TaskHandle_4); | |
| vTaskDelete(TaskHandle_1); // Delete the task using the TaskHandle_1 | |
| } | |
| } | |
| /* Task2 with priority 2 */ | |
| static void MyTask2(void* pvParameters) | |
| { | |
| while(1) | |
| { | |
| Serial.println(F("Task2 Running, Creating Task4")); | |
| xTaskCreate(MyTask4, "Task4", 100, NULL, 4, &TaskHandle_4); | |
| Serial.println(F("Back in Task2, Deleting itself")); | |
| vTaskDelete(NULL); //Delete own task by passing NULL(TaskHandle_2 can also be used) | |
| } | |
| } | |
| /* Task4 with priority 4 */ | |
| static void MyTask4(void* pvParameters) | |
| { | |
| Serial.println(F("Task4 Running, Changing Priority of Task1 from 1-3")); | |
| vTaskPrioritySet(TaskHandle_1,3); //Change the priority of task1 to 3 which is greater than task2 | |
| while(1) | |
| { | |
| Serial.println(F("Back in Task4 ")); | |
| vTaskDelay(100/portTICK_PERIOD_MS); | |
| } | |
| } |
Output
0. Serial port is initialized and 2-Tasks are created with different priorities. Setup message is printed.