Multiple tasks running concurrently in FreeRTOS

Introduction

Running multiple tasks at the same time lets your program do many things together. This makes your device more efficient and responsive.

When you want to read sensors and control motors at the same time.

When you need to handle user input while processing data in the background.

When you want to blink an LED while also communicating over Wi-Fi.

When your program must respond quickly to different events without waiting.

Syntax

FreeRTOS

void Task1(void *pvParameters) {
    for(;;) {
        // Task1 code here
        vTaskDelay(pdMS_TO_TICKS(1000));
    }
}

void Task2(void *pvParameters) {
    for(;;) {
        // Task2 code here
        vTaskDelay(pdMS_TO_TICKS(500));
    }
}

int main(void) {
    xTaskCreate(Task1, "Task 1", 1000, NULL, 1, NULL);
    xTaskCreate(Task2, "Task 2", 1000, NULL, 1, NULL);
    vTaskStartScheduler();
    for(;;);
}

Each task is a function that runs in an infinite loop.

vTaskDelay pauses the task for a set time, letting other tasks run.

Examples

Two tasks: one blinks an LED every 500ms, the other reads a sensor every 1000ms.

FreeRTOS

void BlinkLED(void *pvParameters) {
    for(;;) {
        // Toggle LED
        vTaskDelay(pdMS_TO_TICKS(500));
    }
}

void ReadSensor(void *pvParameters) {
    for(;;) {
        // Read sensor data
        vTaskDelay(pdMS_TO_TICKS(1000));
    }
}

Creating tasks with different priorities: LED task has higher priority (2) than sensor task (1).

FreeRTOS

xTaskCreate(BlinkLED, "LED Task", 1000, NULL, 2, NULL);
xTaskCreate(ReadSensor, "Sensor Task", 1000, NULL, 1, NULL);

Sample Program

This program creates two tasks that print messages at different intervals. Task 1 prints every 1 second, Task 2 every 0.5 seconds. They run together, showing multitasking.

FreeRTOS

#include "FreeRTOS.h"
#include "task.h"
#include <stdio.h>

void Task1(void *pvParameters) {
    for(;;) {
        printf("Task 1 is running\n");
        vTaskDelay(pdMS_TO_TICKS(1000));
    }
}

void Task2(void *pvParameters) {
    for(;;) {
        printf("Task 2 is running\n");
        vTaskDelay(pdMS_TO_TICKS(500));
    }
}

int main(void) {
    xTaskCreate(Task1, "Task 1", 1000, NULL, 1, NULL);
    xTaskCreate(Task2, "Task 2", 1000, NULL, 1, NULL);
    vTaskStartScheduler();
    for(;;);
}

Important Notes

FreeRTOS switches between tasks quickly to make them run together.

Use vTaskDelay to let other tasks run and avoid blocking.

Task priorities help decide which task runs first if both are ready.

Summary

Multiple tasks let your program do many things at once.

Each task runs in a loop and uses vTaskDelay to pause.

FreeRTOS manages task switching automatically.