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GNU/Linux Rapid Embedded Programming

GNU/Linux Rapid Embedded Programming

By : Rodolfo Giometti
4.3 (3)
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GNU/Linux Rapid Embedded Programming

GNU/Linux Rapid Embedded Programming

4.3 (3)
By: Rodolfo Giometti

Overview of this book

Embedded computers have become very complex in the last few years and developers need to easily manage them by focusing on how to solve a problem without wasting time in finding supported peripherals or learning how to manage them. The main challenge with experienced embedded programmers and engineers is really how long it takes to turn an idea into reality, and we show you exactly how to do it. This book shows how to interact with external environments through specific peripherals used in the industry. We will use the latest Linux kernel release 4.4.x and Debian/Ubuntu distributions (with embedded distributions like OpenWrt and Yocto). The book will present popular boards in the industry that are user-friendly to base the rest of the projects on - BeagleBone Black, SAMA5D3 Xplained, Wandboard and system-on-chip manufacturers. Readers will be able to take their first steps in programming the embedded platforms, using C, Bash, and Python/PHP languages in order to get access to the external peripherals. More about using and programming device driver and accessing the peripherals will be covered to lay a strong foundation. The readers will learn how to read/write data from/to the external environment by using both C programs or a scripting language (Bash/PHP/Python) and how to configure a device driver for a specific hardware. After finishing this book, the readers will be able to gain a good knowledge level and understanding of writing, configuring, and managing drivers, controlling and monitoring applications with the help of efficient/quick programming and will be able to apply these skills into real-world projects.
Table of Contents (20 chapters)
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GPIOs in Linux


In a Linux system, GPIO lines can be managed through the sysfs using simple Bash commands; this is the easiest technique we can use to get access to these peripherals. In the following examples, we are going to use the Wandboard but we can redo them on the other systems too but using different GPIO lines, of course.

The sysfs interface to manage the GPIOs are under the /sys/class/gpio/ directory, and if we take a look at its content, we can see the following files:

root@wb:~# ls /sys/class/gpio/
export     gpiochip128  gpiochip192  gpiochip64  unexport
gpiochip0  gpiochip160  gpiochip32   gpiochip96

Files named gpiochip0, gpiochip32, and so on are related to the GPIO controller chips that are the entities that actually manage a GPIOs group. In our case, the Wandboard groups GPIOs by 32 and then each gpiochip takes its name according to the first managed GPIO number. So, gpiochip0 manages GPIOs from 0 to 31, gpiochip32 manages GPIOs from 32 to 63, and so on.

If we take a look...

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