The rubidium atomic clock requires an accurate time source to initially set the time. Originally I used a RS232 GPS puck but I then looked for something home grown. The answer was to use sime NTP Client to obtain the time from an internet time server and send the date and time as text to the atomic clock.
This simple NTP client uses a w5100 ethernet chip and a mega32 for its intelligence.
This site may be personal technical tutorial site about AVR tech.
in this site, there are 3 ethernet module for prototype.
2 are W5100 based modules and 1 is ENC28J60 module.
in detail, please visit http://www.sgitheach.org.uk/exp.html
He also wrote useful example for network moudle like “NTP Client”.
in detail, visit http://www.sgitheach.org.uk/ntp.html
but we’re afraid, there is no source code.
however he opened the hardware schematic.
Schematic and PCB
Source : http://www.sgitheach.org.uk/exp.html