Warren Gay - Advanced Raspberry Pi: Raspbian Linux and GPIO Integration

Warren Gay

Advanced Raspberry Pi Raspbian Linux and GPIO Integration 2nd ed.

For Jackie.

About the Author and About the Technical Reviewer

About the Author

Warren Gay

started out in electronics at an early age, dragging discarded TVs and radios on his way home from public school. In high school he developed a fascination for programming the IBM 1130 computer, which resulted in a career plan change to software development. After attending Ryerson Polytechnical Institute, he has enjoyed a software developer career for over 35 years, programming mainly in C/C++. Warren has been programming Linux since 1994 as an open source contributor and professionally on various Unix platforms since 1987.

Before attending Ryerson, Warren built an Intel 8008 system from scratch before there were CP/M systems and before computers got personal. In later years, Warren earned an advanced amateur radio license (call sign VE3WWG) and worked the amateur radio satellites. A high point of his ham radio hobby was making digital contact with the Mir space station (U2MIR) in 1991.

Warren works at Datablocks.net, an enterprise-class ad serving software services company. There he programs C++ server solutions on Linux back-end systems.

About the Technical Reviewer

Martin Rothwell

has followed his interest in computers from an early age, fascinated by the magic of computers and digital electronics in general. Self-described as too curious for his own good, he would spend many of his early years tinkering with the building of computers and the programming of software. This led naturally to undertaking a degree in computer science, which was completed in 2007. Since then Martin has pursued a career in education and is currently employed as a senior lecturer at The University of Central Lancashire. His thirst for knowledge and need to satisfy his curious nature have led to a healthy obsession with maintaining active self-development.

Martin would like to thank the Raspberry Pi Foundation in general for their efforts and their Pi Academy program for helping to inspire digital making in schools and hopefully helping more of the current generation of younger makers to become fascinated, also, by the magic of computing.

The Raspberry Pi is amazing at two levelsthe advanced functionality that you get in a credit card-sized SBC (Single Board Computer) and its price. Even with todays Pi competitors, the Raspberry Pi reigns supreme because few can beat its price. Further, it enjoys great software and community support.

Price is an important advantage of the Pi that competitors dont always appreciate. Hobbyists and makers are applying the Pi in new and sometimes risky ways. Someone starting out doesnt want to lose their SBC because of a rookie mistake. At the low Pi price point, the loss can be absorbed without losing heart. Imagine a student buying an Intel Joule1 (when it was offered) for $349 USD and toasting it by accident. That would be enough to make most people give up right there! Price allows everyone to proceed fearlessly in their learning.

Before considering the details about the resources within the Raspberry Pi, it is useful to take a high-level inventory. In this chapter, lets list what you get when you purchase a Pi.

In some cases, the hardware will have one or more kernel modules behind it, forming the device driver layer. They expose a software API that interfaces between the application and the hardware device. For example, applications communicate with the driver by using ioctl(2) calls, while the driver communicates with the I2C devices on the bus. The /sys/class file system is another way that device drivers expose themselves to applications. Youll see this when GPIO (general purpose input/output) is examined in Chapter .

There are some cases where drivers dont exist in Raspbian Linux, requiring you to use a bare metal approach . An example of this is creating PWM signals using software. By mapping the GPIO registers into the application memory space, the desired result can be obtained directly from the application program. Both direct access and driver access have their advantages and disadvantages.

So while the summary inventory simply lists the hardware devices, youll be examining each resource in greater detail in the chapters ahead.