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PKGBUILD
README.md
rpi900-rtc.install
rpi900-rtc.service

README.md

Summary (version 1.0-1)

This PKGBUILD and related files form a simple package for enabling the PCF8523 real-time clock on RPi900 boards. A service is provided for automatically synchronising the Raspberry Pi system clock to the real-time clock during system startup.

Operation

During package installation your /boot/config.txt file will be modified to enable the pcf8523-rtc device-tree overlay. With this modification, the PCF8523 chip will be automatically loaded as /dev/rtc0 when the Raspberry Pi boots.

The package also installs a systemd service to synchronise the system time from /dev/rtc0 once it's loaded. (This typically occurs around the 12-second mark.) The service is enabled to run automatically, so no further action is required.

After rebooting, you can observe synchronisation of the clock by typing systemctl status rpi900-rtc:

* rpi900-rtc.service - RPi900 real-time clock synchronisation
   Loaded: loaded (/usr/lib/systemd/system/rpi900-rtc.service; enabled; vendor preset: disabled)
   Active: inactive (dead) since Sun 2015-02-15 14:08:50 AEDT; 2h 29min ago
  Process: 142 ExecStart=/usr/bin/hwclock --hctosys (code=exited, status=0/SUCCESS)
 Main PID: 142 (code=exited, status=0/SUCCESS)

Jan 01 10:00:13 roof systemd[1]: Starting RPi900 real-time clock synchronisation...
Feb 15 14:08:50 roof systemd[1]: Started RPi900 real-time clock synchronisation.

(No reverse synchronisation of the hardware clock from the system clock is performed; the ntpd time protocol should do this automatically if the Raspberry Pi is network-connected.)

Package Contents

The package installs only a single file:

  • /usr/lib/systemd/system/rpi900-rtc.service: this systemd service file performs a system clock synchronisation (hwclock --hctosys) once the hardware clock device becomes available.

Release History

  • 2015/02/15: version 1.0-1: initial release.