Book Image

Hands-On RTOS with Microcontrollers

By : Brian Amos
Book Image

Hands-On RTOS with Microcontrollers

By: Brian Amos

Overview of this book

A real-time operating system (RTOS) is used to develop systems that respond to events within strict timelines. Real-time embedded systems have applications in various industries, from automotive and aerospace through to laboratory test equipment and consumer electronics. These systems provide consistent and reliable timing and are designed to run without intervention for years. This microcontrollers book starts by introducing you to the concept of RTOS and compares some other alternative methods for achieving real-time performance. Once you've understood the fundamentals, such as tasks, queues, mutexes, and semaphores, you'll learn what to look for when selecting a microcontroller and development environment. By working through examples that use an STM32F7 Nucleo board, the STM32CubeIDE, and SEGGER debug tools, including SEGGER J-Link, Ozone, and SystemView, you'll gain an understanding of preemptive scheduling policies and task communication. The book will then help you develop highly efficient low-level drivers and analyze their real-time performance and CPU utilization. Finally, you'll cover tips for troubleshooting and be able to take your new-found skills to the next level. By the end of this book, you'll have built on your embedded system skills and will be able to create real-time systems using microcontrollers and FreeRTOS.
Table of Contents (24 chapters)
Section 1: Introduction and RTOS Concepts
Section 2: Toolchain Setup
Section 3: RTOS Application Examples
Section 4: Advanced RTOS Techniques

Differentiating between tasks and ISRs

Before we jump into coding a peripheral driver that utilizes interrupts, let's take a quick look at how interrupts compare to FreeRTOS tasks.

There are many similarities between tasks and ISRs:

  • Both provide a way of achieving parallel code execution.
  • Both only run when required.
  • Both can be written with C/C++ (ISRs generally no longer need to be written in assembly code).

But there are also many differences between tasks and ISRs:

  • ISRs are brought into context by hardware; tasks gain context by the RTOS kernel: Tasks are always brought into context by the FreeRTOS kernel. Interrupts, on the other hand, are generated by hardware in the MCU. There are usually a few different ways of configuring the generation (and masking) of interrupts.
  • ISRs must exit as quickly as possible; tasks are more forgiving: FreeRTOS tasks are often set up...