Specifications

7.5. RELIABILITY

The presence and status of the power supply is also checked. If the battery

is low and there is no mains power supply, the peripherals are not be started

until the battery has suﬃciently recharged to supply the required power (for

example, the high current requirements of the GSM and RFID modules).

Illegal FSM states If, for whatever reason, one of the afore-mentioned

FSMs’ states should change to an illegal value, the fault would be caught

and the state changed to its initial “idle” condition.

Time-outs Time-outs are implemented for all software and hardware actions.

If a request does not complete within a predeﬁned period (which is adjusted

according to the action to be performed), the request is cancelled and the

operator notiﬁed so that the fault may be corrected.

7.5.2 Hardware

Device recovery in the case of a fault is performed mostly in software. Pure

hardware reliability support is the bare minimum to ensure a successful

system recovery in the event that the microprocessor cannot start (ie it has

no power supply due to a ﬂat battery). The detail of this operation can be

found in Section 8.4.1. Included is a system temperature sensor (which is

also used as part of the battery charging algorithm) and voltage monitoring

of the battery and main power supply.

Also provided is the ability to hard reset the GSM module, either by

pulling a reset line low or by removing its power supply completely. This is

especially useful as the module has “hung” (the device stops responding to

commands, including the software escape sequence “+++”) multiple times

during the testing of the unit.

An on-board in-circuit debugger (ICD) interface is provided to allow in-

ﬁeld reprogramming and debugging.