User Manual

WiData Firefly System Hand Held Communicator User’s Guide
1
Introduction
WiData Firefly System
The Firefly RF Location System is designed to permit users to determine the position of tagged assets in both indoor and
outdoor facilities such as factories and freight yards. The system locates tagged assets by a process involving redundant
triangulation. Each tag autonomously emits a 2.4 GHz direct sequence spread spectrum (DSSS) radio signal at
predetermined blink rate. Each tag’s blink rate is randomized around its predetermined value to minimize the number of
collisions between transmissions made by different tags. The signal emitted by the tag is received by a minimum of four
DSSS receivers each of which are capable of decoding that tag’s transmission. A typical transmission contains a preamble
which is used to synchronize the receiver, the tag’s serial number which identifies the tag, a status word which monitors
various tag functions, data stored in the tag’s memory and finally a CRC used to assure that the tag’s message is correct as
received.
Tag configuration parameters such as blink rate and user data to be stored in memory are loaded into the tag using a
device called a Hand Held Communicator (HHC). The HHC consists of a Type II PCMCIA card inserted into a laptop or
handheld PC. The PCMCIA card contains a short range (2 to 10 feet) radio transmitter and receiver which communicates
with a very low power transmitter and receiver contained in each tag. This short range communication link operates at 2.4
GHz. The modulation scheme used by the PCMCIA card was chosen to minimize power consumption by the battery
operated tag receiver. The DSSS transmitter allows the system to locate users of the HHC anywhere in the service area
covered by the system.
Hand Held Communicator
The WiData Corporation Communicator PCMCIA card allows the handheld computer, laptop computer, or any other
computer with a PCMCIA slot to operate as a Firefly Communicator. Tag-to-Communicator bi-directional data transfers
are accomplished using the OOK/FSK RF modulation link. The Communicator-to-RF Processor DSSS RF modulation
link is one-way only. Figure 1 shows a typical WiData Firefly System. The handheld computer can also include standard
WLAN and Bar Code Scanners to further enhance system capabilities.
Power Management
The Hand Held Communicator PCMCIA power consumption is handled by the application software installed on the
handheld computer. The software will power down the card during periods of in-activity. Any time the Hand Held
Communicator is not in use, the handheld computer should be installed into its battery charging cradle.