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)
1
Section 1: Introduction and RTOS Concepts
5
Section 2: Toolchain Setup
9
Section 3: RTOS Application Examples
13
Section 4: Advanced RTOS Techniques

Avoiding race conditions

So, when do we need to use mutexes and semaphores? Any time there is a shared resource between multiple tasks, either a mutex or a semaphore should be used. Standard binary semaphores can be used for resource protection, so in some special cases (such as semaphores being accessed from ISRs), semaphores can be desirable. However, you must understand how waiting on the semaphore will affect the system.

We'll see an example of a semaphore being used to protect a shared resource in Chapter 10, Drivers and ISRs.

We saw a mutex in action in the previous example, but what would it look like if there was no mutex and we only wanted one of the blue or green LEDs to be on at a time?

Failed shared resource example

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