TrimTrac ProE Locator, Technical Manual

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TrimTrac ProE Locator Technical Manual v2.0e 14
Application Feature Details
The TrimTrac ProE supports a number of important new application features that modify
how the TrimTrac ProE cycles through the basic state machine described in the previous
sections. Before reading this section, it would be useful to have a basic understanding of
the TrimTrac ProE state machine as detailed in State Machine Overview section or,
preferably, the State Machine Design Details section.
Even though the TrimTrac ProE can be used literally out-of-the-box with very little effort
if the factory default settings are used, the device is also highly configurable based on the
particular requirements of any given application. When changing from factory default
settings, constant vigilance must be given to communication cost and power
consumption. It is possible, for instance, to configure the TrimTrac ProE to provide very
rapid reporting, but doing so may result in unacceptably high power consumption and/or
communication costs, especially if SMS is used in lieu of GPRS.
The following sections detail how the application features operate, how to set them up
and what some of the trade offs may be in terms of power consumption and
communication costs. In other sections of this technical manual, specific configuration
recommendations are set for some typical applications scenarios.
Communication Mode
The TrimTrac ProE supports SMS and GPRS data communication via the GSM network
and can be configured to use one or the other exclusively or automatically switch
between the two.
For instance, if the Communication Mode is set 0=SMS-only, then the device will
communicate exclusively via SMS. Alternately, if the Communication Mode is set
1=GPRS-only, the device is able to receive messages via GPRS or SMS, but the device
will use only GPRS to respond. Finally, if the Communication Mode is set 2=Auto-
select, the device is able to receive messages via GPRS or SMS and the device will
respond via GPRS whenever possible; however, if a GSM network is present but GPRS
service is not available, the device will revert to SMS until such time as GPRS service
becomes available.
Note that if GPRS service is enabled by the carrier on a SIM card already in service, the
GSM modem in the TrimTrac may need to be power cycled before the newly enabled
GPRS service becomes active. (See AT+CTKC on page 117; SET_APP_CONFIG on
page 148) .
GPRS Connection and Setup
If GPRS is enabled via the appropriate Communication Mode setting, then the GPRS
connection and setup parameters are used to establish and maintain GPRS sessions. The
TrimTrac ProE supports UDP and TCP transport protocols. UDP is a connection-less
protocol that generally requires less overhead than TCP, but TCP has a number of
advantages that may make it the preferred choice of transport protocol for smaller
deployments.