As a precursor to an 802.15.4 controlled watering system, and to get familiar with the development environment, I am building a clock based around a Jennic JN5139.

So far, I have a timer interrupt firing once every 16x10^6 cycles, or nominally once per second. Measuring the drift over an 8 hour period, the clock has so far lost 1 minute. I'll tweak the timer to account for this drift tonight, after I have more data.

Some ideas to implement:

• Put the CPU into a low power state between timer ticks
• Drive an LED matrix, rather than outputting to the serial port
• Use 6LoWPAN to sync time, maybe via NTP?
• RSS Feeds?