Designing Embedded Hardware

Infrared Communication

So far, we have looked at serial communication that takes place over copper wire. In this section, we’ll look at serial communication using infrared light. 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. Later, we’ll see just how trivial infrared hardware is to implement.

IrDA

IrDA is the infrared transmission standard commonly used in computers and peripherals. IrDA stands for Infrared Data Association, a consortium of more than 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 upon HP-SIR significantly and provides a range of protocols that application software may use in communication.

The basic purpose of IrDA is to provide device-to-device communication over short distances. Mobile devices, such as laptops, present a problem when they must be connected to other machines or networks. Chances are, ...