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

Creating DMA-based drivers

We saw that, compared to a polled approach, the interrupt-based driver is considerably better in terms of CPU utilization. But what about applications with a high data rate that require millions of transfers per second? The next step in improved efficiency can be obtained by having the CPU involved as little as possible by pushing most of the work for transferring data around onto specialized peripheral hardware within the MCU.

A short introduction to DMA was covered in Chapter 2, Understanding RTOS Tasks, in case you need a refresher before diving into this example.

In this example, we'll work through creating a driver using the same buffer-based interface as the interrupt-based driver. The only difference will be the use of DMA hardware to transfer bytes out of the peripheral's read data register (RDR) and into our buffer. Since we already...