HVAC Control in the New Millennium.pdf - HVAC.Amickracing

HVAC Control in the New MillenniumIrDA ControlThe Infrared Data Association (IrDA) Control technology is a command-and-controlarchitecture for communication with wireless peripheraldevices. It has an operating range of approximately 7-m. This systemis oriented toward control data packets. It is not intended to passfiles.The IrDA Control system is a polled-host topology. The host devicepolls up to eight peripheral devices in an ordered sequence, providingservice requests and handling the peripheral-device responses. The hostcan be personal computers with peripheral devices such as a mouse andkeyboard. After the system boots up, the keyboard and mouse operatewith the host PC in the same manner as a wired keyboard and mouse.Portable devices are using low-cost, high-speed, wireless connectivityto support interoperability. Infrared (IR) technology can be embeddedinto portable devices such as notebook computers, personal digitalassistants (PDAs), wireless phones and digital cameras. It can offer valuableHVAC system maintenance features including walk-up interrogation,file transfer and network access. To ensure platforminteroperability, the Infrared Data Association communications standardis optimized for low-cost, short-range, point-to-point communications.The IrDA standard communications protocol is defined to minimizecode size and maximize efficiency. There are several operatingspeeds and modulation schemes.IR technology in wireless systems offers some advantages over RFtechnology. These include lower communications subsystem parts cost,smaller physical space and no Federal Communications Commission(FCC) testing and approval requirements. IR-equipped devices also supportmore secure data transmissions since they provide shorter coverageranges and IR light cannot escape areas enclosed by walls.The IrDA standard covers interoperability by addressing the softwarelayers and physical modulation schemes needed for transmission.The hardware includes an IR controller and a transceiver. The controllerhas the following functions:• interface to the system bus,• converts data from parallel to serial,• executes the modulation and demodulation needed, and• performs external transceiver control.©2001 by The Fairmont Press, Inc. All rights reserved.