I hate having to set clocks. Most of our clocks at home get the time from Internet or from the DCF77 time signal.
The problem with the DCF77 time signal is that it is quite sensitive to environmental noise from lamps or other appliances, and the reception inside buildings can be problematic in some places.
I recently installed a clock in such a location. Using Udo Klein's DCF77 analysis tool it was clear that it would be nearly impossible to get the clock to work properly as initially planned, so I started looking for solutions:
- bigger antenna (eg this one)
- external antenna
- external receiver
- different time source
For different reasons, the only viable option seemed to be a different time source. But I did not want to change the clock design. While researching a solution, I came across the Chronvertor. Although this would allow to run the clock without DCF77 signal, the clock would still have to be set from time to time (due to lack of precision of the RTC, but at least twice per year for DST adjustments), so I quickly dismissed that option. However it provided inspiration for what I eventually ended up building: a NTP to DCF77 "adapter".
I had experimented previously with the TimeNTP example from the Arduino Time library, and there was plenty of information available online about the DCF77 signal, so this quickly appeared to be a viable option. This is the result: ntp2dcf.ino.
instead of including wiring.h, WProgram.h, WConstants.h and pins_arduino.h, you only need Arduino.h
Wire.send() is now Wire.write(), Wire.receive() is now Wire.read()
If you get error messages like "call of overloaded ‘write(int)’ is ambiguous", you probably need to add "(byte)" before a constant argument, eg: Wire.write((byte)0x00);
It is possible to use conditional statements to write code that is compatible with older and newer versions, eg:
