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

Direct task notifications

Queues are an excellent workhorse of an RTOS because of their flexibility. Sometimes, all of this flexibility isn't needed and we'd prefer a more lightweight alternative. Direct task notifications are similar to the other communication mechanisms discussed, except that they do not require the communication object to first be instantiated in RAM. They are also faster than semaphores or queues (between 35% and 45% faster).

They do have some limitations, the largest two being that only one task can be notified at a time and notifications can be sent by ISRs but not received.

Direct task notifications have two main components: the notification itself (which behaves very much like how a semaphore or queue behaves when unblocking a task) and a 32-bit notification value. The notification value is optional and has a few different uses. A notifier has...