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

RTOS semaphores

Semaphores are another very straightforward, but powerful, construct. The word semaphore has a Greek origin the approximate English translation is sign-bearer, which is a wonderfully intuitive way to think about them. Semaphores are used to indicate that something has happened; they signal events. Some example use cases of semaphores include the following:

  • An ISR is finished servicing a peripheral. It may give a semaphore to provide tasks with a signal indicating that data is ready for further processing.
  • A task has reached a juncture where it needs to wait for other tasks in the system to catch up before moving on. In this case, a semaphore could be used to synchronize the tasks.
  • Restricting the number of simultaneous users of a restricted resource.

One of the convenient aspects of using an RTOS is the pre-existence of semaphores. They are included...