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© 2010 Microchip Technology Inc.DS01071B-page 1

AN1071

INTRODUCTION

Infrared communication is a low-cost method of

providing wireless, point-to-point communication

between two devices. The Infrared Data Association,

often referred to as IrDA, was formed in 1994 to

develop standard methods for communicating over

short-range infrared transmissions. These standards

have continued to evolve and gain in popularity. Now, a

wide variety of devices implement the IrDA standard

specification, including computers, printers, PDAs, cell

phones, watches and other instruments.

Microchip’s 16-bit and 32-bit microcontrollers are a

perfect fit for applications wanting to support IrDA

standard communication. These low-cost

microcontrollers, with their built-in IrDA standard

support, provide an inexpensive solution with plenty of

computing power.

IrDA® STANDARD

Overview

The IrDA standard specification is a half-duplex

communication protocol with Serial Infrared (SIR)

transmission speeds similar to those supported by an

RS-232 port (9600 bps, 19.2kbps, 38.4 kbps,

57.6 kbps and 115.2 kbps). Microchip currently

supports only the SIR transmission speeds.

The half-duplex nature of the communications is due to

the fact that the receiver is blinded by the light of its own

transmitter. The infrared transceiver transmits pulses in

a cone with a half-angle between 15 and 30 degrees

(Figure 1). The pulses must be visible from a distance

of one meter, but must not be so bright that the receiver

is overwhelmed at close distances. In practice, optimal

positioning for a receiver is usually a distance of 5 cm

to 60cm from the transmitter, in the center of the

transmission cone.

Protocols

The initial specifications developed by the Infrared

Data Association provided a mechanism for converting

existing serial interfaces to infrared interfaces. These

protocols closely mimic standard serial interfaces. As

the infrared communication mechanism gained

popularity, more protocols were created to tailor the

communication format for different types of end

applications.

The infrared communication support is designed as a

Stack. Figure 2 shows the basic structure of the Stack.

FIGURE 1:OPTICAL PORT ANGLES

Author:Kim Otten

Microchip Technology Inc.

15-30 Degrees Half-Angle≥ 15 Degrees Half-Angle

ReceiverTransmitter

IrDA® Standard Stack for Microchip 16-bit and

32-bit Microcontrollers

Product specificaties