rpiclock

Tardis image credit: jeayese

The Raspberry Pi is a convenient, inexpensive device for driving a HD display and I thought it would be fun to use one for a time display. So I wrote rpiclock (pronounced with a silent 'r').

It has a few interesting features, most of them configurable via a setup file:

• Shows local, UTC, GPS time and Unix time.
• The format of the time shown can be HH:MM:SS or HH:MM, 12 or 24 hours,and with a blinking/non-blinking separator.
• Can automatically fetch a leap second table so that it can calculate GPS time.
• Shows 23:59:60 when a leap second addition occurs.
• Powers down the display at programmed times to save power and the monitor (works properly with RPi+LCD monitor, not correctly on PCs).
• You can use a nice background image and a logo on the clock and the font colour can be changed to suit the background image.
• In slideshow mode, the image is randomly chosen from a specified directory.
• There's an event mode, where a picture can be shown on a particular day(s) eg a picture of the boss on her birthday.
• It doesn't show the time if the host is unsynchronised, as determined by querying ntpd.
• The display can dim, according to a number in a file written by another process eg a process measuring the ambient light level. Useful in a lecture theatre for example, where the lights may be dimmed for a presentation and you don't want the display to be distractingly bright.
• The configuration file is re-reread every time it is changed and (most) changes are then applied.

There's also a context menu so you can experiment with settings (and quit when in full-screen mode).

There are no special tricks to make sure that the clock updates at the correct time - the software just uses a QTimer (usleep() at the bottom?) to wake up at the right time. The latency and jitter are a few milliseconds typically. It usually skips a second when loading a new image since this can be abit slow.

I've had rpiclock driving a wall-mounted Dell S2340L since May 2013. I fretted a bit about image burn in at first, but that doesn't seem to be happening; maybe the power save mode (it only runs during working hours) helps with that.

You may need to customise the layout of the graphics a bit if you have an alternate logo that you want to use. The logo I designed for is 300 by 228 pixels.

If you find a bug let me know.

Download rpiclock source code here. There are some instructions and setup hints in the README. Yup, no binaries.