Book Image

Mastering Embedded Linux Programming - Third Edition

By : Frank Vasquez, Chris Simmonds
5 (3)
Book Image

Mastering Embedded Linux Programming - Third Edition

5 (3)
By: Frank Vasquez, Chris Simmonds

Overview of this book

If you’re looking for a book that will demystify embedded Linux, then you’ve come to the right place. Mastering Embedded Linux Programming is a fully comprehensive guide that can serve both as means to learn new things or as a handy reference. The first few chapters of this book will break down the fundamental elements that underpin all embedded Linux projects: the toolchain, the bootloader, the kernel, and the root filesystem. After that, you will learn how to create each of these elements from scratch and automate the process using Buildroot and the Yocto Project. As you progress, the book will show you how to implement an effective storage strategy for flash memory chips and install updates to a device remotely once it’s deployed. You’ll also learn about the key aspects of writing code for embedded Linux, such as how to access hardware from apps, the implications of writing multi-threaded code, and techniques to manage memory in an efficient way. The final chapters demonstrate how to debug your code, whether it resides in apps or in the Linux kernel itself. You’ll also cover the different tracers and profilers that are available for Linux so that you can quickly pinpoint any performance bottlenecks in your system. By the end of this Linux book, you’ll be able to create efficient and secure embedded devices using Linux.
Table of Contents (27 chapters)
1
Section 1: Elements of Embedded Linux
10
Section 2: System Architecture and Design Decisions
18
Section 3: Writing Embedded Applications
22
Section 4: Debugging and Optimizing Performance

Receiving NMEA messages over SPI

NMEA is a data message format supported by most GPS receivers. The ZOE-M8Q outputs NMEA sentences by default. These sentences are ASCII text, starting with the $ character, followed by comma-separated fields. Raw NMEA messages are not always easy to read, so we will use a parser to add helpful annotations to the data fields.

What we want to do is read the stream of NMEA sentences from the ZOE-M8Q out of the /dev/spidev0.0 interface. Since SPI is full-duplex, this also means writing to /dev/spidev0.0, although we can simply write the same 0xFF value over and over again. There is a program called spi-pipe that is designed to do this sort of thing. It is part of the spi-tools package, along with spi-config. Rather than relying on spi-pipe, I chose to modify spidev-test so that it streams the ASCII input from the GPS module to stdout. The source for my spidev-read program can be found in this book's code archive, inside the MELP/Chapter12/spidev...