GPS-based NTP server

Setting up the server software is not hard, ntpd can work with NMEA strings coming in from a GPS receiver. The problem is that there will be random time delays imposed by the serial port and the operating system, so getting closer than about 10 ms is not easy.

The MX-9212 does have a PPS output; I always wondered what that was for. It's a TTL output on the back panel that can be connected to the host computer to give a more accurate time base.

Somewhere or other I saw an article on what to do with this signal. I need to find it.

I need to wire it up to an input on the UNIX side that is processed in realtime. Should be interesting.