GPS time-beacon (clock that sends time over xbee)

[linux-works]

part of my IoT series of experiments and hacks.

it gets time from a ublox neo-7m series gps module, keeps time in the DS3231 rtc module, displays to a 1" oled display (white, behind orange filter) and broadcasts time in checksummed-ascii datagrams over xbee.

any other client who is tuned to that xbee PAN can get the updates and set their local clock from this.

a client that boots up can also do a GET over xbee and not have to wait for the next broadcast interval.