Issue
138 January 2002
WHAT
GOOD IS IrD,Eh?
PART
1: CORDLESS PROTOCOL
byJeff
Bachiochi
The IrDA
has been hard at work creating a host of protocols.
In the first part of this series, Jeff looks at the
protocol that covers the requirements of the physical
cordless hardware.
Start
•
Standards Make It Happen •
IrPHY
• The Range •
UART To IrDA • IR
Encoder/Decoder •
Gimme More • Sources
& PDF
The Infrared
Data Association would have you believe we need wireless
data communications using infrared light. Most of us automatically
think, "Infrared, oh yeah, my TV remote uses IR." After
all, those hand-held timesaving devices that help support
our couch potato lifestyle communicate using a 40-kHz
modulated infrared beam.
The data rate
of your IR remote is not what would be considered high.
It doesn’t have to be high to command changing a channel
or muting a commercial. Typical IrDA communication deals
with moving more information than just changing the channel.
And so IrDA continues to evolve, beginning with serial
infrared (SIR) (115 Kbps or less), adding fast infrared
(FIR) (up to 4 Mbps), and looking toward very fast IR
(VFIR) (16 Mbps). The IrDA standard does not include TV
remote communication.
The Infrared
Data Association is the non-profit trade association with
representatives from computer and telecommunications hardware,
software, components, and adapter companies throughout
the world. Like most standards organizations, the IrDA
ensures interoperability between all types of devices.
In this case, it regards devices using infrared light
to communicate. The present standard requires devices
to be in proximity to one another. That is, within line
of sight and not more than 1 m between transceivers. What
this assures is a secure, one-to-one connection. Doesn’t
this seem limited to you?
You might be
thinking that you could do this by just making a direct
connection between devices. And you’d be correct, at least
for limited applications using agreed on hardware and
universal connectors. But, you have to look at the bigger
picture.
By using the
IrDA standards, the physical connections are no longer
necessary. That removes the fragile connector and cable
from potential problems. This allows the engineers to
focus on their devices and not how they will interface
with all other possibilities. It isn’t hard to imagine
how devices could easily interact with one another. Today’s
PCs and notebooks communicate with printers and PDAs.
Soon your credit card may be transacting with ATMs and
such via line-of-sight IR communications.
