RTOS

Introduction

Thought I would do a page on RTOS so I have the terminology right. May do the same for Zephyr and Embassy to see how they compare.

RTOS Platforms

For me I have come across the different platforms

• Zephyr running on my Nordic boards
• FreeRTOS no used but the course drove me to this
• IDF RTOS running on my ESP32 (not sure the difference)

Arduino

I guess most people of familiar with the Arduino approach to software with sketches. I dislike the ecosystem and try to avoid it but this is what the course used.

void foo1() {
  // Do some function
}

void foo2() {
  // Do some function
}

void setup() {
  // Do some setup
}

void loop() {
  // Do something forever
  foo1();
  foo2();
}

Using Arduino with RTOS

The purpose of this page we will use only one processor, whereas the ESP32 I am using has two. To disable this we will use the following code. It will be omitted from code examples to save space.

// Use only core 1 for demo purposes
#if CONFIG_FREERTOS_UNICORE
static const BaseType_t app_cpu = 0;
#else
static const BaseType_t app_cpu = 1;
#endif

Tasks

In RTOS a task is a unit of work. It have these states

To create a task we use the following code.

 // Task to run forever
  xTaskCreatePinnedToCore(  // Use xTaskCreate() in vanilla FreeRTOS
              toggleLED_1,  // Function to be called
              "Toggle 1",   // Name of task
              1024,         // Stack size (bytes in ESP32, words in FreeRTOS)
              NULL,         // Parameter to pass to function
              1,            // Task priority (0 to configMAX_PRIORITIES - 1)
              NULL,         // Task handle
              app_cpu);     // Run on one core for demo purposes (ESP32 only)

I guess this is mainly self explanatory. There are other APIs to create a task. I have used xTaskCreate, but I think we are using this to ensure only on CPU is useda task