If you have ever used a remote control, you have used infrared technology. Infrared is a wireless communication technology that makes use of the invisible spectrum of light that is just beyond red in the visible spectrum. It’s suitable for applications that require short-range, point-to-point data transfer. Because it uses light, line of sight is a prerequisite for using infrared. Despite this limitation, infrared is widely used in household equipment and is increasingly popular in devices such as digital cameras, PDAs, and notebook computers.
Founded in 1993 as a nonprofit organization, the Infrared Data Association (IrDA) is an international organization that creates and promotes interoperable, low-cost infrared data interconnection standards that allow users to point one device at another and have it just work. The Infrared Data Association standards support a broad range of appliances, computing, and communications devices.
Tip
The term IrDA is typically used to refer to the protocols for infrared communications, not exclusively to the nonprofit body.
In this chapter, I take a look at Windows XP’s support for infrared and show how you can make use of it for your daily tasks.
There are currently four versions of IrDA; their differences are mainly in the transfer speed. They are:
- Serial Infrared (SIR)
This is the original standard with a transfer speed of up to 115 Kbps.
- Medium Infrared (MIR)
Improved transfer speed of 1.152 Mbps. Not widely implemented.
- Fast Infrared (FIR)
Speed of up to 4 Mbps. Most new computers implement this standard. Windows 2000 and XP support this implementation.
- Very Fast Infrared (VFIR)
Future versions of the IrDA will boost speed up to 50 Mbps.
When two devices with two different IrDA implementations communicate with each other, they will both step down to the lower transfer speed.
In terms of operating range, infrared devices can communicate up to one or two meters. Depending on the implementation, if a device uses a lower power version, the range can be stepped down to a mere 20 to 30 cm. This is crucial for low-power devices.
All data packets exchanged are protected using a Cyclic Redundancy Check (CRC), which uses a number derived from the transmitted data to verify its integrity. CRC-16 is used for speeds up to 1.152 Mbs and CRC-32 is used for speeds up to 4 Mbs. The IrDA also defines a bi-directional communication for infrared communications.