LBS +System Clock Synchronisation Overview

Introduction

The GPS signal contains accurate time +data. LBS can use this data to synchronise the system clock with GPS. The +system clock is synchronised with GPS at regular intervals if the difference +between GPS time and the system clock time exceeds a threshold time difference.

Key concepts

System clock: The mobile device clock that keeps system time.
Set clock plug-in DLL: An optional licensee ECom plug-in DLL used by LBS to set the system +clock. Symbian provides a default class that sets the system clock by calling User::SetUTCTime().

It +is only necessary to implement a set clock plug-in DLL if a licensee requires +to set the system clock by some means other than by calling User::SetUTCTime().

Whether +LBS uses a plug-in DLL or the Symbian default class is configured through +the LBS administration +service.
UTC: Co-ordinated Universal Time. A worldwide time standard. UTC is derived +from the GPS signal and is the time standard used to set the system clock.

API Summary

There are two separate APIs involved +with LBS system clock adjustment:

The LBS Set Clock Plug-in +Interface

Licensees can derive from the interface to create an implementation +class. The class is packaged as an ECom plug-in DLL which is loaded at startup +and used to set the system clock.
Automatic clock synchronisation

The LBS Set Clock Plug-in Interface

LBS defines +an interface class that is used to create a set clock plug-in DLL.

The +interface CGPSSetClockBase is shown in figure 2.

+ Figure 2. CGPSSetClockBase is the interface for LBS set +clock plug-in classes. + +

To create a set clock plug-in, licensees create a class that derives +from CGPSSetClockBase and package it as an ECom DLL.

See How to implement a LBS set +clock plug-in DLL for more information.

Automatic clock synchronisation

LBS can perform +automatic synchronisation of the system clock. LBS administration settings +configure automatic clock synchronisation. The settings define the frequency +of automatic clock synchronisation and by how much the system clock and UTC +can differ before the clock is synchronised.

LBS system clock settings

LBS +administration describes how to configure LBS system clock synchronisation +settings using either the LBS Administration API or a repository initialisation +file.