PPS pin
~~~~~~~

Some GPS receivers have a PPS pin.
This can be used to get a very accurate time reference.
According to `Wikipedia <https://en.wikipedia.org/wiki/Pulse-per-second_signal>`_ this signal could be considered a "stratum-1 time source".

The signal on the PPS pin is a high pulse of +/- 100 msec and the rising edge signals the start of a second.
The time reported after this pulse describes the past rising edge of the PPS pulse.

.. note:: Currently the PPS feature is not thoroughly tested yet, so consider it experimental.