Learn Freertos - 10 Code Examples & CST Typing Practice Test

FreeRTOS is a lightweight, open-source real-time operating system (RTOS) kernel for embedded devices. It provides multitasking, scheduling, and inter-task communication for microcontrollers and small processors.

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Hello World Task (FreeRTOS)Blink LED Task (FreeRTOS)Queue Example (FreeRTOS)Mutex Example (FreeRTOS)Timer Callback (FreeRTOS)Semaphore Synchronization (FreeRTOS)Task Delay Example (FreeRTOS)Queue Set Example (FreeRTOS)Priority Task Example (FreeRTOS)Event Group Example (FreeRTOS)

Learn FREERTOS with Real Code Examples

Updated Nov 27, 2025

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Code Sample Descriptions

Hello World Task (FreeRTOS)

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

void vTask(void* pvParameters) {
    printf("Hello, FreeRTOS!\n");
    vTaskDelete(NULL);
}

int main() {
    xTaskCreate(vTask, "Task1", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
    vTaskStartScheduler();
    return 0;
}

Basic FreeRTOS task printing Hello World.

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Blink LED Task (FreeRTOS)

#include <FreeRTOS.h>
#include <task.h>
#include <stdint.h>
#include "gpio.h"

void vBlinkTask(void* pvParameters) {
    while(1) {
        GPIO_TogglePin(LED_PIN);
        vTaskDelay(pdMS_TO_TICKS(500));
    }
}

int main() {
    xTaskCreate(vBlinkTask, "Blink", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
    vTaskStartScheduler();
    return 0;
}

Toggles an LED using a FreeRTOS task.

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Queue Example (FreeRTOS)

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

QueueHandle_t xQueue;

void vSenderTask(void* pvParameters) {
    int value = 42;
    xQueueSend(xQueue, &value, portMAX_DELAY);
    vTaskDelete(NULL);
}

void vReceiverTask(void* pvParameters) {
    int received;
    xQueueReceive(xQueue, &received, portMAX_DELAY);
    printf("Received: %d\n", received);
    vTaskDelete(NULL);
}

int main() {
    xQueue = xQueueCreate(1, sizeof(int));
    xTaskCreate(vSenderTask, "Sender", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
    xTaskCreate(vReceiverTask, "Receiver", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
    vTaskStartScheduler();
    return 0;
}

Shows sending and receiving messages via FreeRTOS queue.

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Mutex Example (FreeRTOS)

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

SemaphoreHandle_t xMutex;

void vTask1(void* pvParameters) {
    xSemaphoreTake(xMutex, portMAX_DELAY);
    printf("Task1 in critical section\n");
    xSemaphoreGive(xMutex);
    vTaskDelete(NULL);
}

void vTask2(void* pvParameters) {
    xSemaphoreTake(xMutex, portMAX_DELAY);
    printf("Task2 in critical section\n");
    xSemaphoreGive(xMutex);
    vTaskDelete(NULL);
}

int main() {
    xMutex = xSemaphoreCreateMutex();
    xTaskCreate(vTask1, "T1", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
    xTaskCreate(vTask2, "T2", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
    vTaskStartScheduler();
    return 0;
}

Demonstrates mutual exclusion using FreeRTOS mutex.

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Timer Callback (FreeRTOS)

#include <FreeRTOS.h>
#include <timers.h>
#include <stdio.h>

void vTimerCallback(TimerHandle_t xTimer) {
    printf("Timer callback triggered\n");
}

int main() {
    TimerHandle_t xTimer = xTimerCreate("Timer", pdMS_TO_TICKS(1000), pdTRUE, NULL, vTimerCallback);
    xTimerStart(xTimer, 0);
    vTaskStartScheduler();
    return 0;
}

Sets up a FreeRTOS software timer with a callback function.

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Semaphore Synchronization (FreeRTOS)

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

SemaphoreHandle_t xBinarySem;

void vTaskProducer(void* pvParameters) {
    printf("Producer giving semaphore\n");
    xSemaphoreGive(xBinarySem);
    vTaskDelete(NULL);
}

void vTaskConsumer(void* pvParameters) {
    xSemaphoreTake(xBinarySem, portMAX_DELAY);
    printf("Consumer received semaphore\n");
    vTaskDelete(NULL);
}

int main() {
    xBinarySem = xSemaphoreCreateBinary();
    xTaskCreate(vTaskProducer, "Producer", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
    xTaskCreate(vTaskConsumer, "Consumer", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
    vTaskStartScheduler();
    return 0;
}

Uses a binary semaphore to synchronize two tasks.

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Task Delay Example (FreeRTOS)

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

void vTaskDelayExample(void* pvParameters) {
    while(1) {
        printf("Task running\n");
        vTaskDelay(pdMS_TO_TICKS(1000));
    }
}

int main() {
    xTaskCreate(vTaskDelayExample, "DelayTask", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
    vTaskStartScheduler();
    return 0;
}

Demonstrates delaying a task for a fixed period.

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Queue Set Example (FreeRTOS)

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

QueueHandle_t xQueue1, xQueue2;
QueueSetHandle_t xQueueSet;

int main() {
    xQueue1 = xQueueCreate(1, sizeof(int));
    xQueue2 = xQueueCreate(1, sizeof(int));
    xQueueSet = xQueueCreateSet(2);
    xQueueAddToSet(xQueue1, xQueueSet);
    xQueueAddToSet(xQueue2, xQueueSet);
    vTaskStartScheduler();
    return 0;
}

Demonstrates using a FreeRTOS queue set to manage multiple queues.

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Priority Task Example (FreeRTOS)

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

void vHighPriorityTask(void* pvParameters) {
    printf("High priority task running\n");
    vTaskDelete(NULL);
}

void vLowPriorityTask(void* pvParameters) {
    printf("Low priority task running\n");
    vTaskDelete(NULL);
}

int main() {
    xTaskCreate(vLowPriorityTask, "Low", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
    xTaskCreate(vHighPriorityTask, "High", configMINIMAL_STACK_SIZE, NULL, 2, NULL);
    vTaskStartScheduler();
    return 0;
}

Creates two tasks with different priorities to demonstrate scheduling.

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Event Group Example (FreeRTOS)

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

EventGroupHandle_t xEventGroup;

int main() {
    xEventGroup = xEventGroupCreate();
    xEventGroupSetBits(xEventGroup, 0x01);
    printf("Event bit set\n");
    vTaskStartScheduler();
    return 0;
}

Shows using FreeRTOS event groups for task synchronization.

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Frequently Asked Questions about Freertos

What is Freertos?

What are the primary use cases for Freertos?

Task scheduling for embedded systems. IoT and sensor node software. Industrial automation control. Real-time motor and sensor management. Edge devices and microcontroller applications

What are the strengths of Freertos?

Very lightweight (few KB footprint). Highly portable across MCUs. Open-source with active community. Predictable real-time behavior. Easy integration with peripheral drivers

What are the limitations of Freertos?

Not a full-featured OS (no file system, GUI). Limited memory protection features. Requires careful design for hard real-time tasks. Debugging complex task interactions can be tricky. No native networking stack (requires integration)

How can I practice Freertos typing speed?

CodeSpeedTest offers 10+ real Freertos code examples for typing practice. You can measure your WPM, track accuracy, and improve your coding speed with guided exercises.

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Code Sample Descriptions

Hello World Task (FreeRTOS)

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

void vTask(void* pvParameters) {
    printf("Hello, FreeRTOS!\n");
    vTaskDelete(NULL);
}

int main() {
    xTaskCreate(vTask, "Task1", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
    vTaskStartScheduler();
    return 0;
}

Basic FreeRTOS task printing Hello World.

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Blink LED Task (FreeRTOS)

#include <FreeRTOS.h>
#include <task.h>
#include <stdint.h>
#include "gpio.h"

void vBlinkTask(void* pvParameters) {
    while(1) {
        GPIO_TogglePin(LED_PIN);
        vTaskDelay(pdMS_TO_TICKS(500));
    }
}

int main() {
    xTaskCreate(vBlinkTask, "Blink", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
    vTaskStartScheduler();
    return 0;
}

Toggles an LED using a FreeRTOS task.

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Queue Example (FreeRTOS)

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

QueueHandle_t xQueue;

void vSenderTask(void* pvParameters) {
    int value = 42;
    xQueueSend(xQueue, &value, portMAX_DELAY);
    vTaskDelete(NULL);
}

void vReceiverTask(void* pvParameters) {
    int received;
    xQueueReceive(xQueue, &received, portMAX_DELAY);
    printf("Received: %d\n", received);
    vTaskDelete(NULL);
}

int main() {
    xQueue = xQueueCreate(1, sizeof(int));
    xTaskCreate(vSenderTask, "Sender", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
    xTaskCreate(vReceiverTask, "Receiver", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
    vTaskStartScheduler();
    return 0;
}

Shows sending and receiving messages via FreeRTOS queue.

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Mutex Example (FreeRTOS)

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

SemaphoreHandle_t xMutex;

void vTask1(void* pvParameters) {
    xSemaphoreTake(xMutex, portMAX_DELAY);
    printf("Task1 in critical section\n");
    xSemaphoreGive(xMutex);
    vTaskDelete(NULL);
}

void vTask2(void* pvParameters) {
    xSemaphoreTake(xMutex, portMAX_DELAY);
    printf("Task2 in critical section\n");
    xSemaphoreGive(xMutex);
    vTaskDelete(NULL);
}

int main() {
    xMutex = xSemaphoreCreateMutex();
    xTaskCreate(vTask1, "T1", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
    xTaskCreate(vTask2, "T2", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
    vTaskStartScheduler();
    return 0;
}

Demonstrates mutual exclusion using FreeRTOS mutex.

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Timer Callback (FreeRTOS)

#include <FreeRTOS.h>
#include <timers.h>
#include <stdio.h>

void vTimerCallback(TimerHandle_t xTimer) {
    printf("Timer callback triggered\n");
}

int main() {
    TimerHandle_t xTimer = xTimerCreate("Timer", pdMS_TO_TICKS(1000), pdTRUE, NULL, vTimerCallback);
    xTimerStart(xTimer, 0);
    vTaskStartScheduler();
    return 0;
}

Sets up a FreeRTOS software timer with a callback function.

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Semaphore Synchronization (FreeRTOS)

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

SemaphoreHandle_t xBinarySem;

void vTaskProducer(void* pvParameters) {
    printf("Producer giving semaphore\n");
    xSemaphoreGive(xBinarySem);
    vTaskDelete(NULL);
}

void vTaskConsumer(void* pvParameters) {
    xSemaphoreTake(xBinarySem, portMAX_DELAY);
    printf("Consumer received semaphore\n");
    vTaskDelete(NULL);
}

int main() {
    xBinarySem = xSemaphoreCreateBinary();
    xTaskCreate(vTaskProducer, "Producer", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
    xTaskCreate(vTaskConsumer, "Consumer", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
    vTaskStartScheduler();
    return 0;
}

Uses a binary semaphore to synchronize two tasks.

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Task Delay Example (FreeRTOS)

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

void vTaskDelayExample(void* pvParameters) {
    while(1) {
        printf("Task running\n");
        vTaskDelay(pdMS_TO_TICKS(1000));
    }
}

int main() {
    xTaskCreate(vTaskDelayExample, "DelayTask", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
    vTaskStartScheduler();
    return 0;
}

Demonstrates delaying a task for a fixed period.

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Queue Set Example (FreeRTOS)

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

QueueHandle_t xQueue1, xQueue2;
QueueSetHandle_t xQueueSet;

int main() {
    xQueue1 = xQueueCreate(1, sizeof(int));
    xQueue2 = xQueueCreate(1, sizeof(int));
    xQueueSet = xQueueCreateSet(2);
    xQueueAddToSet(xQueue1, xQueueSet);
    xQueueAddToSet(xQueue2, xQueueSet);
    vTaskStartScheduler();
    return 0;
}

Demonstrates using a FreeRTOS queue set to manage multiple queues.

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Priority Task Example (FreeRTOS)

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

void vHighPriorityTask(void* pvParameters) {
    printf("High priority task running\n");
    vTaskDelete(NULL);
}

void vLowPriorityTask(void* pvParameters) {
    printf("Low priority task running\n");
    vTaskDelete(NULL);
}

int main() {
    xTaskCreate(vLowPriorityTask, "Low", configMINIMAL_STACK_SIZE, NULL, 1, NULL);
    xTaskCreate(vHighPriorityTask, "High", configMINIMAL_STACK_SIZE, NULL, 2, NULL);
    vTaskStartScheduler();
    return 0;
}

Creates two tasks with different priorities to demonstrate scheduling.

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Event Group Example (FreeRTOS)

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

EventGroupHandle_t xEventGroup;

int main() {
    xEventGroup = xEventGroupCreate();
    xEventGroupSetBits(xEventGroup, 0x01);
    printf("Event bit set\n");
    vTaskStartScheduler();
    return 0;
}

Shows using FreeRTOS event groups for task synchronization.

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Frequently Asked Questions about Freertos

What is Freertos?

What are the primary use cases for Freertos?

Task scheduling for embedded systems. IoT and sensor node software. Industrial automation control. Real-time motor and sensor management. Edge devices and microcontroller applications

What are the strengths of Freertos?

Very lightweight (few KB footprint). Highly portable across MCUs. Open-source with active community. Predictable real-time behavior. Easy integration with peripheral drivers

What are the limitations of Freertos?

How can I practice Freertos typing speed?

CodeSpeedTest offers 10+ real Freertos code examples for typing practice. You can measure your WPM, track accuracy, and improve your coding speed with guided exercises.