Designing Embedded Hardware, 2nd Edition

Chapter 10. IrDA

It makes all the difference whether one sees darkness through the light or brightness through the shadows.

—David Lindsay, A Voyage to Arcturus

In the last chapter, we looked at serial communication that takes place over copper wire. Now, we'll see a serial interface that uses pulses of infrared light to transmit data across short distances, without the need for interconnecting cables. Infrared (IR) transmission of data is becoming commonplace, and IR transceivers are appearing in laptop computers, PDAs, and cell phones. They are also appearing in peripherals such as printers and network interfaces, allowing no-fuss/no-cable connection for people on the move. IR communication is also used by remote controls to talk to their appliances. Your TV, VCR, and DVD remotes all have an IR LED to beam commands across the room.

We'll start our discussion of IR communication by looking at the most common standard, IrDA. Later, we'll see just how trivial infrared hardware is to implement.

Introduction to IrDA

IrDA is the infrared transmission standard commonly used in computers and peripherals. IrDA, which stands for "Infrared Data Association," is a consortium of over 150 companies that maintain and develop the standard. IrDA owes it origins to the infrared communication links used in Hewlett-Packard calculators, known as HP-SIR (Hewlett-Packard Serial Infra Red). The IrDA standard has expanded on HP-SIR significantly and provides a range of protocols that application ...