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4

Infrared

Communications

Overview

Infrared (IR) radiation lies between the visible and microwave por-
tions of the electromagnetic spectrum, and is the medium that the per-
sonal digital assistant (PDA) uses to talk to the robot control circuitry
(see Figure 4.1).
IR light is broken into the following three categories.

• Near-infrared (near-IR)—Closest to visible light, near-IR has
wavelengths that range from 0.7 to 1.3 microns, or 700 billionths
to 1300 billionths of a meter.
• Mid-infrared (mid-IR)—Mid-IR has wavelengths ranging from 1.3
to 3 microns. Both near-IR and mid-IR are used by a variety of
electronic devices, including remote controls. It is in this mid
range that the PDA will communicate with the robotic body using
the Infrared Data Association (IrDA) communication protocol.

• Thermal-infrared (thermal-IR)—Occupying the largest part of the
IR spectrum, thermal-IR has wavelengths ranging from 3 microns
to over 30 microns.
The infrared emitters (IREDs) used for PDA devices fall into the near-
IR category.
PDABot will use an IrDA protocol called IrCOMM (9-wire “cooked”
service class) and the IrLMP. To simplify the task of using the IrDA

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