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Time on an Embedded Device

• Introduction
• External Time Sources
• Install Required Time Conversion files

Introduction

For a device to keep correct time with Qtopia requires the following:

1. the kernel must support a Real-Time Clock (RTC) interface and be built with the correct driver for the device RTC.
2. the Linux distribution must contain /sbin/hwclock that accepts the -s and -w parameters.
3. boot scripts set system-time from hardware-time on startup /sbin/hwclock -s.

Note: These processes should be tested on the device prior to Qtopia controlling them.

External Time Sources

Devices may that have readily available external time sources, such as:

• GSM Cell Tower Time
• NTP IP Network Time

Such devices should report such updates by sending a storeExternalSource(QString,uint,int,int) message to the TimeUpdate service.

Currently, only one external source is supported.

If no external source is available, the user will need to set the time shortly after start-up, and the RTC will need to be sufficiently reliable.

Install Required Time Conversion files

Qtopia requires Time Conversion data such as in <qtopia-root-dir>/etc/zoneinfo to be on the device. To install the Time Conversion data files either:

1. Create a symbolic link to the Time Conversion data files provided by Qtopia, for example, on the device run:

       if [ ! -d /usr/share/zoneinfo ]; then ln -s /opt/Qtopia/etc/zoneinfo /usr/share/zoneinfo; fi

2. Create a symbolic link to the Time Conversion data files provided by the device's environment, for example, on the device run:

       if [ -d /usr/share/zoneinfo ]; then rm -rf /opt/Qtopia/etc/zoneinfo; ln -s /usr/share/zoneinfo /opt/Qtopia/etc/zoneinfo ; fi

3. If the Time Conversion data cannot be uploaded to the device's root file system modify the value of QTOPIA_ZONEINFO_PATH in the device's custom.h to point to where the Time Conversion data files are stored.