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

Replacing malloc and free

Many C runtimes will ship with an implementation of malloc, but the embedded, oriented versions won't necessarily be thread safe by default. Because each C runtime is different, the steps needed to make malloc thread safe will vary. The included STM toolchain used in this book includes newlib-nano as the C runtime library. The following are a few notes regarding newlib-nano:

  • newlib-nano uses malloc and realloc for stdio.h functionality (that is, printf).
  • realloc is not directly supported by FreeRTOS heap implementations.
  • FreeRTOSConfig.h includes the configUSE_NEWLIB_REENTRANT setting to make newlib thread safe, but it needs to be used in conjunction with the appropriate implementations of all stubs. This will allow you to use newlib-based printf, strtok, and so on in a thread-safe manner. This option also makes general use case calls to malloc...