![\"ESP32](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/07\/ESP32-FreeRTOS-Getting-Started.jpg?resize=1200%2C675&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\nIn this tutorial, we’ll cover the following topics:<\/p>\n\n\n\n
- \n
- What is FreeRTOS<\/a>\n
- \n
- Why is FreeRTOS useful with the ESP32?<\/a><\/li>\n\n\n\n
- FreeRTOS Basic Concepts<\/a><\/li>\n<\/ul>\n<\/li>\n\n\n\n
- 1) Creating Tasks<\/a><\/li>\n\n\n\n
- 2) Suspend and Resume Tasks<\/a><\/li>\n\n\n\n
- 3) Creating and Running Multiple Tasks<\/a><\/li>\n\n\n\n
- 4) Creating and Running Multiple Tasks (Dual Core)<\/a><\/li>\n\n\n\n
- 5) Tasks Memory Usage<\/a><\/li>\n<\/ul>\n\n\n\n
Prerequisites<\/h2>\n\n\n\n
This tutorial focuses on programming the ESP32 using the Arduino core. Before proceeding, you should have the ESP32 Arduino core installed in your Arduino IDE. Follow the next tutorial to install the ESP32 on the Arduino IDE, if you haven\u2019t already.<\/p>\n\n\n\n
- \n
- Installing the ESP32 Board in Arduino IDE (Windows, Mac OS X, and Linux instructions)<\/a><\/li>\n<\/ul>\n\n\n\n
\n\n\n\nWhat is FreeRTOS?<\/h2>\n\n\n\n
FreeRTOS is a lightweight, open-source real-time operating system (RTOS). It provides a framework for running multiple tasks concurrently<\/strong>, each with its own priority <\/strong>and execution schedule<\/strong>. Instead of running code line by line, FreeRTOS lets you create independent tasks that the ESP32 can switch between quickly based on the task priority.<\/p>\n\n\n
\n![\"FreeRTOS](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/07\/Logo_freeRTOS.png?resize=413%2C157&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\nIt also provides tools like queues <\/strong>and semaphores <\/strong>so tasks can seamlessly communicate with each other.<\/p>\n\n\n\n
This makes your code more organized and responsive, especially when your ESP32 is handling several tasks at the same time, like reading sensors, handling HTTP requests, and displaying information on a screen, while listening to interrupts.<\/p>\n\n\n\n
Why is FreeRTOS useful with the ESP32?<\/h3>\n\n\n\n
The FreeRTOS real-time operating system is built into the ESP32 and integrated into the Espressif IDF and the Arduino core. It supports:<\/p>\n\n\n\n
- \n
- Task Management<\/strong>: create, suspend, resume, or delete tasks (covered in this tutorial).<\/li>\n\n\n\n
- Scheduling<\/strong>: allows you to give priority to your tasks, so they run in a specific order (covered in this tutorial).<\/li>\n\n\n\n
- Inter-Task Communication<\/strong>: using things like queues, semaphores, and mutexes, we can ensure seamless communication between tasks without crashing the ESP32.<\/li>\n\n\n\n
- Dual-Core Support<\/strong>: it allows you to run your tasks on either core 0 or core 1 of the ESP32 (also covered in this tutorial, but for a more in-depth guide about using dual-core with the ESP32, check this guide: How to use ESP32 Dual Core with Arduino IDE<\/a>).<\/li>\n<\/ul>\n\n\n\n
So, in summary…<\/p>\n\n\n\n
FreeRTOS is useful with the ESP32 because it enables multitasking, allowing multiple tasks like sensor reading, Wi-Fi, and display updates to run without blocking each other. <\/p>\n\n\n\n
It also allows you to take advantage of the ESP32 dual-core processor by letting you assign tasks to specific cores for better performance. <\/p>\n\n\n\n
Additionally, with priority-based scheduling, time-critical tasks can run immediately, making it ideal for real-time applications when you need to react quickly to external events detected by the ESP32 GPIOs. <\/p>\n\n\n\n
FreeRTOS Basic Concepts<\/h3>\n\n\n\n
Before diving into the practical examples, let’s cover some basic concepts related to FreeRTOS:<\/p>\n\n\n\n
- \n
- Tasks<\/strong>: tasks are independent functions running concurrently, each with its own stack (memory usage allocated) and priority. Tasks can be in states like Running, Ready, Blocked, or Suspended.<\/li>\n\n\n\n
- Scheduler<\/strong>: the scheduler decides which tasks to run based on their priorities. This is a preemptive scheduler, which means it can interrupt a lower-priority task at any time to run a higher-priority one, ensuring that critical tasks are executed as soon as they’re ready.<\/li>\n\n\n\n
- Priorities<\/strong>: higher numbers indicate higher priority (for example: 1 = low, 5 = high).<\/li>\n<\/ul>\n\n\n\n
\n\n\n\n1) Creating Tasks<\/h2>\n\n\n\n
This is the simplest example in which we’ll show you how to create a FreeRTOS task to blink an LED every second. We’ll connect the LED to GPIO 2. Instead, you can skip the LED and check the results on the ESP32 built-in LED.<\/p>\n\n\n\n
Parts Required<\/h3>\n\n\n\n
For this example, you need the following parts:<\/p>\n\n\n\n
- \n
- ESP32 Board<\/a> \u2013 read Best ESP32 Development Boards<\/a><\/li>\n\n\n\n
- LED<\/a><\/li>\n\n\n\n
- 220 Ohm resistor<\/a> (or similar values)<\/li>\n\n\n\n
- Breadboard<\/a><\/li>\n\n\n\n
- Jumper wires<\/a><\/li>\n<\/ul>\n\n\n
You can use the preceding links or go directly to MakerAdvisor.com\/tools<\/a> to find all the parts for your projects at the best price!<\/p>
![](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/10\/header-200.png?w=1200&quality=100&strip=all&ssl=1\")
<\/a><\/p>\n\n\n\nWiring the Circuit<\/h3>\n\n\n\n
Wire an LED to GPIO 2 as shown in the following schematic diagram.<\/p>\n\n\n
\n![\"ESP32](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/07\/ESP32-connected-to-an-LED_bb-edited.png?resize=729%2C846&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\nESP32: Creating FreeRTOS Tasks – Arduino Code<\/h3>\n\n\n\n
The following code creates a task that will blink an LED connected to GPIO 2 every second.<\/p>\n\n\n
\/*\n Rui Santos & Sara Santos - Random Nerd Tutorials\n Complete project details at https:\/\/RandomNerdTutorials.com\/esp32-freertos-arduino-tasks\/\n Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files.\n The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.\n*\/\n#define LED_PIN 2\n\n\/\/ Declare task handle\nTaskHandle_t BlinkTaskHandle = NULL;\n\nvoid BlinkTask(void *parameter) {\n for (;;) { \/\/ Infinite loop\n digitalWrite(LED_PIN, HIGH);\n Serial.println("BlinkTask: LED ON");\n vTaskDelay(1000 \/ portTICK_PERIOD_MS); \/\/ 1000ms\n digitalWrite(LED_PIN, LOW);\n Serial.println("BlinkTask: LED OFF");\n vTaskDelay(1000 \/ portTICK_PERIOD_MS);\n Serial.print("BlinkTask running on core ");\n Serial.println(xPortGetCoreID());\n }\n}\n\nvoid setup() {\n Serial.begin(115200);\n \n pinMode(LED_PIN, OUTPUT);\n\n xTaskCreatePinnedToCore(\n BlinkTask, \/\/ Task function\n "BlinkTask", \/\/ Task name\n 10000, \/\/ Stack size (bytes)\n NULL, \/\/ Parameters\n 1, \/\/ Priority\n &BlinkTaskHandle, \/\/ Task handle\n 1 \/\/ Core 1\n );\n}\n\nvoid loop() {\n \/\/ Empty because FreeRTOS scheduler runs the task\n}<\/code><\/pre>\n\tView raw code<\/a><\/p>\n\n\n\n
How Does the Code Work?<\/h3>\n\n\n\n
We start by defining the GPIO that will be connected to the LED.<\/p>\n\n\n\n
#define LED_PIN 2<\/code><\/pre>\n\n\n\nTask Handle<\/h4>\n\n\n\n
Then, declare the task handle. A TaskHandle_t<\/span> is a variable that points to a FreeRTOS task, letting you control it, like resuming it, stopping it, or delete it. In this example, we won’t need the task handle, but we’re creating it nonetheless to show you how it’s done.<\/p>\n\n\n\n
TaskHandle_t BlinkTaskHandle = NULL;<\/code><\/pre>\n\n\n\nTask Function<\/h4>\n\n\n\n
Then, we create a task. A task is nothing more than a function that executes whatever commands you want. Here’s the BlinkTask<\/span> function used in this example.<\/p>\n\n\n\n
void BlinkTask(void *parameter) {\n for (;;) { \/\/ Infinite loop\n digitalWrite(LED_PIN, HIGH);\n Serial.println(\"BlinkTask: LED ON\");\n vTaskDelay(1000 \/ portTICK_PERIOD_MS); \/\/ 1000ms\n digitalWrite(LED_PIN, LOW);\n Serial.println(\"BlinkTask: LED OFF\");\n vTaskDelay(1000 \/ portTICK_PERIOD_MS);\n Serial.print(\"BlinkTask running on core \");\n Serial.println(xPortGetCoreID());\n }\n}<\/code><\/pre>\n\n\n\nThis function is a FreeRTOS task, which is a special kind of function that runs independently under the FreeRTOS scheduler, allowing multitasking on the ESP32.<\/p>\n\n\n\n
FreeRTOS tasks must return void and must accept a single argument, which can be used to pass data to the function (not used in our case).<\/p>\n\n\n\n
void BlinkTask(void *parameter) {<\/code><\/pre>\n\n\n\nThe for(;;)<\/span> creates an infinite loop to ensure the task runs indefinitely until explicitly stopped. This is similar to the loop()<\/span> function used in Arduino code.<\/p>\n\n\n\n
for (;;) { \/\/ Infinite loop<\/code><\/pre>\n\n\n\nThen, we use the digitalWrite()<\/span> function to turn the LED on and off. Notice that instead of using the typical delay()<\/span> function, we use vTaskDelay()<\/span>.<\/p>\n\n\n\n
digitalWrite(LED_PIN, HIGH);\nSerial.println(\"BlinkTask: LED ON\");\nvTaskDelay(1000 \/ portTICK_PERIOD_MS); \/\/ 1000ms\ndigitalWrite(LED_PIN, LOW);\nSerial.println(\"BlinkTask: LED OFF\");\nvTaskDelay(1000 \/ portTICK_PERIOD_MS);<\/code><\/pre>\n\n\n\nvTaskDelay()<\/h4>\n\n\n\n
vTaskDelay()<\/span> is a FreeRTOS function that pauses a task for a specified number of ticks, allowing other tasks to run during that time. It doesn’t block your code like delay()<\/span>. The vTaskDelay()<\/span> function accepts ticks. On the ESP32, each tick is typically 1ms (defined by portTICK_PERIOD_MS<\/span>), so vTaskDelay(1000 \/ portTICK_PERIOD_MS)<\/span> pauses the task for 1000ms (1 second).<\/p>\n\n\n\n
vTaskDelay(1000 \/ portTICK_PERIOD_MS);<\/code><\/pre>\n\n\n\nGet Core IDE<\/h4>\n\n\n\n
For demonstration purposes, we also print in which core the task is running. We can get that information by calling the xPortGetCoreID()<\/span> function.<\/p>\n\n\n\n
Serial.print(\"BlinkTask running on core \");\nSerial.println(xPortGetCoreID());<\/code><\/pre>\n\n\n\nsetup()<\/h4>\n\n\n\n
In the setup()<\/span>, we initialize the Serial Monitor and set the LED as an output.<\/p>\n\n\n\n
void setup() {\n Serial.begin(115200);\n \n pinMode(LED_PIN, OUTPUT);<\/code><\/pre>\n\n\n\nCreate a Task<\/h4>\n\n\n\n
Now, to actually create a FreeRTOS task and assign it to a specific core, we need to use the xTaskCreatePinnedToCore()<\/span> function. This function also specifies the task function, name, stack size, parameters, priority, and task handle.<\/p>\n\n\n\n
xTaskCreatePinnedToCore(\n BlinkTask, \/\/ Task function\n \"BlinkTask\", \/\/ Task name\n 10000, \/\/ Stack size (bytes)\n NULL, \/\/ Parameters\n 1, \/\/ Priority\n &BlinkTaskHandle, \/\/ Task handle\n 1 \/\/ Core 1\n);<\/code><\/pre>\n\n\n\nThe task function is BlinkTask<\/span> that we defined earlier. We can also give a name to the task. In this case, “BlinkTask”<\/span>. <\/p>\n\n\n\n
BlinkTask, \/\/ Task function\n\"BlinkTask\", \/\/ Task name<\/code><\/pre>\n\n\n\nWe set the task stack size to 10000 bytes. The task stack size is the amount of memory allocated for the task to store its variables, function calls, and temporary data while it runs, ensuring it has enough space to operate without crashing the ESP32. It is defined in bytes. In a later example, we’ll see how to get the stack size of a task.<\/p>\n\n\n\n
10000, \/\/ Stack size (bytes)<\/code><\/pre>\n\n\n\nIn this case, our task doesn’t have any parameters, so we set that parameter to NULL<\/span>.<\/p>\n\n\n\n
NULL, \/\/ Parameters<\/code><\/pre>\n\n\n\nWe give the task priority 1<\/span>. The higher the number, the higher the priority. In this case, it doesn’t matter much because we only have one task.<\/p>\n\n\n\n
1, \/\/ Priority<\/code><\/pre>\n\n\n\nWe also define the task handle for the task that we created at the beginning of the code.<\/p>\n\n\n\n
&BlinkTaskHandle, \/\/ Task handle<\/code><\/pre>\n\n\n\nAnd finally, we define in which core we want to run the task. The ESP32 has two cores, designated core 0 and core 1. In this example, we’re using core 1.<\/p>\n\n\n\n
1 \/\/ Core 1<\/code><\/pre>\n\n\n\nloop()<\/h4>\n\n\n\n
The loop()<\/span> is empty because the FreeRTOS scheduler will run the task. However, it is possible to add code to the loop()<\/span> to run any other commands you want.<\/p>\n\n\n\n
void loop() {\n \/\/ Empty because FreeRTOS scheduler runs the task\n}<\/code><\/pre>\n\n\n\nDemonstration<\/h3>\n\n\n\n
Upload the code to your ESP32 board. After uploading, open the Serial Monitor at a baud rate of 115200. You should get a similar result.<\/p>\n\n\n
\n![\"ESP32](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/07\/ESP32-Running-single-task-demonstration-serial-monitor.png?resize=748%2C369&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\nAt the same time, the LED should be blinking every second.<\/p>\n\n\n\n
![\"ESP32](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/07\/ESP32-with-an-LED-off.jpg?ssl=1\")
<\/figure><\/div>![\"ESP32](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/07\/ESP32-with-an-LED-on.jpg?ssl=1\")
<\/figure><\/div><\/div><\/div><\/div><\/div>\n\n\n\n
\n\n\n\n2) Suspend and Resume Tasks<\/h2>\n\n\n\n
In this example, you\u2019ll learn how to suspend and resume a FreeRTOS task on the ESP32. We\u2019ll create a task that blinks an LED, and use a pushbutton to control it. When the button is pressed, the task will be suspended to stop the blinking, and pressing it again will resume the task.<\/p>\n\n\n\n
Parts Required<\/h3>\n\n\n\n
For this example, you need the following parts:<\/p>\n\n\n\n
- \n
- ESP32 Board<\/a> \u2013 read Best ESP32 Development Boards<\/a><\/li>\n\n\n\n
- LED<\/a><\/li>\n\n\n\n
- 220 Ohm resistor<\/a> (or similar values)<\/li>\n\n\n\n
- Pushubutton<\/a><\/li>\n\n\n\n
- Breadboard<\/a><\/li>\n\n\n\n
- Jumper wires<\/a><\/li>\n<\/ul>\n\n\n\n
Wiring the Circuit<\/h3>\n\n\n\n
Add a pushbutton to your previous circuit. We’re connecting the pushbutton to GPIO 23, but you can use any other suitable GPIO.<\/p>\n\n\n
\n![\"ESP32](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/07\/ESP32-connected-to-an-LED-and-pushbutton_bb.png?resize=771%2C857&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\nRecommended reading: ESP32 Pinout Reference: Which GPIO pins should you use? <\/a><\/p>\n\n\n\n
ESP32: Suspend and Resume FreeRTOS Tasks – Arduino Code<\/h3>\n\n\n\n
The following code listens to the press of a pushbutton to either suspend or resume the blinking FreeRTOS task.<\/p>\n\n\n
\/*\n Rui Santos & Sara Santos - Random Nerd Tutorials\n Complete project details at https:\/\/RandomNerdTutorials.com\/esp32-freertos-arduino-tasks\/\n Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files.\n The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.\n*\/\n#define LED1_PIN 2\n#define BUTTON_PIN 23\n\n\/\/ Task handle\nTaskHandle_t BlinkTaskHandle = NULL;\n\n\/\/ Volatile variables for ISR\nvolatile bool taskSuspended = false;\nvolatile uint32_t lastInterruptTime = 0;\nconst uint32_t debounceDelay = 100; \/\/ debounce period\n\nvoid IRAM_ATTR buttonISR() {\n \/\/ Debounce\n uint32_t currentTime = millis();\n if (currentTime - lastInterruptTime < debounceDelay) {\n return;\n }\n lastInterruptTime = currentTime;\n\n \/\/ Toggle task state\n taskSuspended = !taskSuspended;\n if (taskSuspended) {\n vTaskSuspend(BlinkTaskHandle);\n Serial.println("BlinkTask Suspended");\n } else {\n vTaskResume(BlinkTaskHandle);\n Serial.println("BlinkTask Resumed");\n }\n}\n\nvoid BlinkTask(void *parameter) {\n for (;;) { \/\/ Infinite loop\n digitalWrite(LED1_PIN, HIGH);\n Serial.println("BlinkTask: LED ON");\n vTaskDelay(1000 \/ portTICK_PERIOD_MS); \/\/ 1000ms\n digitalWrite(LED1_PIN, LOW);\n Serial.println("BlinkTask: LED OFF");\n Serial.print("BlinkTask running on core ");\n Serial.println(xPortGetCoreID());\n vTaskDelay(1000 \/ portTICK_PERIOD_MS);\n }\n}\n\nvoid setup() {\n Serial.begin(115200);\n\n\n \/\/ Initialize pins\n pinMode(LED1_PIN, OUTPUT);\n pinMode(BUTTON_PIN, INPUT_PULLUP); \/\/ Internal pull-up resistor\n\n \/\/ Attach interrupt to button\n attachInterrupt(digitalPinToInterrupt(BUTTON_PIN), buttonISR, FALLING);\n\n \/\/ Create task\n xTaskCreatePinnedToCore(\n BlinkTask, \/\/ Task function\n "BlinkTask", \/\/ Task name\n 10000, \/\/ Stack size (bytes)\n NULL, \/\/ Parameters\n 1, \/\/ Priority\n &BlinkTaskHandle, \/\/ Task handle\n 1 \/\/ Core 1\n );\n}\n\nvoid loop() {\n \/\/ Empty because FreeRTOS scheduler runs the task\n}<\/code><\/pre>\n\t - LED<\/a><\/li>\n\n\n\n
- LED<\/a><\/li>\n\n\n\n
- Scheduler<\/strong>: the scheduler decides which tasks to run based on their priorities. This is a preemptive scheduler, which means it can interrupt a lower-priority task at any time to run a higher-priority one, ensuring that critical tasks are executed as soon as they’re ready.<\/li>\n\n\n\n
- Scheduling<\/strong>: allows you to give priority to your tasks, so they run in a specific order (covered in this tutorial).<\/li>\n\n\n\n
- Task Management<\/strong>: create, suspend, resume, or delete tasks (covered in this tutorial).<\/li>\n\n\n\n
- FreeRTOS Basic Concepts<\/a><\/li>\n<\/ul>\n<\/li>\n\n\n\n
- Why is FreeRTOS useful with the ESP32?<\/a><\/li>\n\n\n\n
![\"ESP32](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/07\/Pause-Resume-Task-with-pushbutton.jpg?resize=750%2C421&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n