User's Manual

DRAFT TrimTrac 1.5 Technical Manual v0.3ab 18
Input Modes
Both the Vehicle Adapter and Control Modules support three priority types of switch
closure inputs: High, Medium and Low Priorities. In addition to the Automatic and
Disabled Modes, two new modes of operation have been added as described below.
See AT+CTKY Module-only Application Configuration on page 97 and
SET_MODULE_APP_CONFIG on page 121.
Automatic Mode
When set to automatic, any activated alert can only be silenced after an
acknowledgement is received from the server application. This level of
acknowledgement protocol takes into account that not all packets and messages
delivered by the TrimTrac 1.5 to the GSM network necessarily make it to their final
destination in an uncorrupted format. The use of TCP/IP helps mitigate, but not
eliminate, the risk that a message sent from the TrimTrac 1.5 might not make
through. The only way to get true confirmation that the server application receive
the message is for the server application to positively confirm back to the TrimTrac
1.5 that the message had indeed arrived safely. When set to “Automatic”, the
TrimTrac 1.5 will continuously re-transmit priority alert messages until
acknowledged, or cleared, by the server application.
Network Acknowledgement
If an application requires a less stringent level of send-receive acknowledgement,
then the Alert Mode can be set to “Network Acknowledgement”. In this mode, it is
assumed that the application server has also received any message that is confirmed
to have been received by the GSM network. This provides a lower level of delivery
certainly, but if used with TCP/IP in particular, may provide an acceptable level of
acknowledgement.
.
When set to “2=Network Acknowledgement”, the TrimTrac 1.5 will accept an
acknowledgment directly from the GSM protocol stack that the message had been
sent to the GSM network and, presumably, received by the server application. Given
the store-and-forward, non-guaranteed deliver nature of SMS and UDP, however,
relying upon a GSM network acknowledgement may be risky. Use of TCP/IP over
GPRS provides an added layer of delivery certainly compared to both SMS and
UDP. The only way to guarantee that the server application has received the alert
message, regardless of which protocol is used, remains the application level
acknowledgement protocol enabled when the input mode is set “0=Automatic”.
Monitor-only
When the input mode is set “3=Monitor-only”, activation of the input will not in and
by itself cause a new message to be transmitted to the server application. Rather, the
status of the input will be indicated all subsequent position and status messages that
the TrimTrac would otherwise send to the server application. No