Using FreeRTOS with AVR

Hi techies and hobbyists,

We are excited to work with a nice freeRTOS port for Arduino and AVR based microcontrollers by Felipu. Given below are the steps to use this amazing library with Arduino boards.


We changed our Arduino development platform to PlatformIO and found it a good IDE for both beginners and professionals, having good features such as code completion and real-time semantic error checking using Lint and Clang tools.  For getting started with PlatformIO refer to our earlier blog post.

Users can either install the freeRTOS library using the platform.ini file generated using the project manager or can use the terminal to install the required libraries.

platformio.ini — -home-dhanish-Documents-ArduinoSamples-FreertosTest — Atom_085.png

# Using platform.ini file

lib_deps = 507

# Using library Id

platformio lib install 507

# Using library Name

platformio lib install “FreeRTOS”


Upload the following sample code and check whether everything works fine.

#include <Arduino_FreeRTOS.h>

// define two tasks for Blink & AnalogRead
void TaskBlink( void *pvParameters );
void TaskAnalogRead( void *pvParameters );

// the setup function runs once when you press reset or power the board
void setup() {

  // initialize serial communication at 9600 bits per second:

  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB, on LEONARDO, MICRO, YUN, and other 32u4 based boards.

  // Now set up two tasks to run independently.
    ,  (const portCHAR *)"Blink"   // A name just for humans
    ,  128  // This stack size can be checked & adjusted by reading the Stack Highwater
    ,  NULL
    ,  2  // Priority, with 3 (configMAX_PRIORITIES - 1) being the highest, and 0 being the lowest.
    ,  NULL );

    ,  (const portCHAR *) "AnalogRead"
    ,  128  // Stack size
    ,  NULL
    ,  1  // Priority
    ,  NULL );

  // Now the task scheduler, which takes over control of scheduling individual tasks, is automatically started.

void loop()
  // Empty. Things are done in Tasks.

/*---------------------- Tasks ---------------------*/

void TaskBlink(void *pvParameters)  // This is a task.
  (void) pvParameters;

  Turns on an LED on for one second, then off for one second, repeatedly.

  Most Arduinos have an on-board LED you can control. On the UNO, LEONARDO, MEGA, and ZERO
  it is attached to digital pin 13, on MKR1000 on pin 6. LED_BUILTIN takes care
  of use the correct LED pin whatever is the board used.

  The MICRO does not have a LED_BUILTIN available. For the MICRO board please substitute
  the LED_BUILTIN definition with either LED_BUILTIN_RX or LED_BUILTIN_TX.
  e.g. pinMode(LED_BUILTIN_RX, OUTPUT); etc.

  If you want to know what pin the on-board LED is connected to on your Arduino model, check
  the Technical Specs of your board  at

  This example code is in the public domain.

  modified 8 May 2014
  by Scott Fitzgerald

  modified 2 Sep 2016
  by Arturo Guadalupi

  // initialize digital LED_BUILTIN on pin 13 as an output.

  for (;;) // A Task shall never return or exit.
    digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
    vTaskDelay( 1000 / portTICK_PERIOD_MS ); // wait for one second
    digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
    vTaskDelay( 1000 / portTICK_PERIOD_MS ); // wait for one second

void TaskAnalogRead(void *pvParameters)  // This is a task.
  (void) pvParameters;

  Reads an analog input on pin 0, prints the result to the serial monitor.
  Graphical representation is available using serial plotter (Tools > Serial Plotter menu)
  Attach the center pin of a potentiometer to pin A0, and the outside pins to +5V and ground.

  This example code is in the public domain.

  for (;;)
    // read the input on analog pin 0:
    int sensorValue = analogRead(A0);
    // print out the value you read:
    vTaskDelay(1);  // one tick delay (15ms) in between reads for stability

After running the sample code you can see that the LED is blinking per second. You may think that the program is similar to a conversional blink LED program. Open the Serial terminal with 9600 as baudrate and see the output. Mindblowing!! right??. LED blinking and Serial port printing at the same time!!. Explore the power of RealTime OS and FreeRTOS.


FreeRTOS getting started

PlatformIO freeRTOS installation guide

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