You're reading from Hands-On RTOS with Microcontrollers Create high-performance, real-time embedded systems using FreeRTOS, STM32 MCUs, and SEGGER debug tools

Product type Paperback

Published in Sep 2025

Publisher Packt

ISBN-13 9781803237725

Length 570 pages

Edition 2nd Edition

Languages

Concepts

Operating Systems

Authors (2):

Jim Yuill

Penn Linder

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Table of Contents (27) Chapters

Preface

1. Part 1: Introduction to RTOSes, the Dev-Board, and Tools

2. Introducing Real-Time Systems FREE CHAPTER

3. Introducing the Development Board

4. Introducing the Development-Tools

5. Understanding Super-Loops

6. Implementing the Super-Loop

7. Part 2: The FreeRTOS Scheduler, Tasks, and Primary APIs

8. Understanding RTOS Tasks

9. Running the FreeRTOS Scheduler

10. Protecting Data and Synchronizing Tasks

11. Intertask Communication

12. Part 3: Using FreeRTOS to Build Systems

13. Drivers and ISRs

14. More Efficient Drivers and ISRs

15. Sharing Hardware Peripherals among Tasks

16. Creating Loose Coupling with Queues

17. Part 4: System Design and Troubleshooting

18. FreeRTOS Memory Management

19. Multi-Processor and Multi-Core Systems

20. Troubleshooting Tips and Next Steps

21. Part 5: Reference Information and FreeRTOS Installation

22. Other Books You May Enjoy

23. Index

Appendix A: Tools Quick-Reference

1. Appendix B: Reference Information

2. Appendix C: Creating FreeRTOS Projects, and Installing FreeRTOS

Semaphores

We’ve mentioned several times now that tasks are meant to be programmed so that they’re running in parallel. This means that, by default, they have no relation to one another in time. No assumptions can be made as to where tasks are in their execution with respect to one another – unless they are explicitly synchronized. Semaphores are one mechanism that’s used to provide synchronization between tasks.

Semaphores are presented in the following two sections. The first section describes semaphores conceptually. The second section shows how to use FreeRTOS’s semaphores, via example-programs.

Understanding semaphores

Semaphores are a 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...