User's Manual

GlobalTrak ™ GT Lite Operation and Maintenance Manual
2.2 GT Lite Detailed Software Description
Device Logic and Event Handling
The GT Lite is designed to enable tracking and monitoring of a container or similar asset no
matter its location on the planet, and provide immediate notification through terrestrial
communication links when onboard sensors detect an intrusion or suspicious event. This
task is generally accomplished on internal battery power only, as such much of the time the
main processor is efficiently reading sensor outputs then powering transceivers and the GPS
receiver only when necessary.
GT Lite is controlled by two processors a main processor and a low power controller. The
main processor handles the application code, including creating messages, transmitting
messages, and controlling GPS. The low power controller handles sensor and wireless
interfaces. This includes checking sensor outputs against thresholds, recording sensor values,
and connecting to wireless ZigBee networks.
Sensor Data Acquisition
The sensor values are made known to the low power controller on a frequent basis; however
the sensor data is only recorded into non-volatile memory only when reporting. The sensor
data is combined with time and location information to create a Logger Message and is placed
into the transmit queue as well as logged into non-volatile memory.
Event Handling
Should the low power controller detect an event, for example if a threshold is exceeded, a
Logging Message is immediately generated and handled according to the transmission modes
detailed below. The events include the following:
 OPTIC: threshold level reached on the optical sensor
 SHOCK: threshold level reached on the accelerometer.
 DOOR: door open detected.
 TEMPERATURE LEVEL: one of the temperature level thresholds reached.
 LOW BATTERY: when device battery reaches a configurable state of charge
 STARTUP: immediately follows soft/cold boot
 ANTENNA: GPS Antenna disconnected
 MOUNT: Enclosure removed from its mount
 MOTION: GT Lite determined to be moving by motion sensor
 EXTERNAL ANALOG: one of the external analog level thresholds reached.
 EXTERNAL DIGITAL I/O: change of state on the external digital I/O
 EXTERNAL POWER: presence of external power is detected
 ZIGBEE: a ZigBee level threshold is reached.
Prepared: R. Straz Date: July 25, 2007 Page 28 of
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