Building iPhone and iPad Electronic Projects

Chapter 2. Accessing the Other Built-in Sensors

About This Chapter

Prerequisites

The programs in this chapter are adaptations of the accelerometer from Chapter 1; read it first if this chapter seems confusing.

Equipment

You will need an iPhone, iPod, or iPad running iOS 5 or later.

Software

You will need a copy of techBASIC or techBASIC Sampler.

What You Will Learn

This chapter shows how to access the magnetometer and gyroscope built into most iOS devices. You can use them for anything from direction finding to augmented reality.

Toward the end of the chapter you’ll also learn a bit more about techBASIC, including another way to access the sensors that gives faster response times and how to use the techBASIC help system to find out more about these and other commands.

The chapter closes with a quick look at two other services. While not sensors in the traditional sense, they are accessed that way. One is GPS, and the other is heading, which uses the magnetometer and compass to find direction.

Writing our first GUI-based program to display sensor data from the iPhone and iPad in Chapter 1 was a bit involved. After all, you were learning a new programming environment as well as learning about the sensors. With that basic knowledge (pardon the pun), it’s time to quickly expand what we can do. Among other things, we need to finish our tricorder!

The Gyroscope

Starting with the iPhone 4, all iPhones include a three-axis gyroscope. You might think a gyroscope is unnecessary, since ...