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NMEA GGA RMC GGK - 18

Description

Driver for decoding NMEA UTC Time tags for the purpose of Qinsy Time Synchronization. This driver only decodes time tags and positions; further time related tasks like setting the clock and interfacing the Qinsy Time Synchronization Adapter are handled elsewhere.

A single driver and serial port can be used to decode positions and time tags, this is only possible for a certain driver though. (as of April 2012).

The driver gives priority to ZDA messages over the position messages. As soon as it detects and decodes a ZDA message it will accept time tags only from this message type.

The Qinsy time synchronization assumes, and therefore relies on, the reported time tag, whether from a ZDA or a GGA/RMC/GGK, corresponds to the exact moment that it was transmitted on the serial or network port, i.e. with the smallest latency possible. If for instance the GPS receiver reports a GGA message with 800 millisecond latency the time synchronization will be off by 800 msec when no Time Synchronization pulse (PPS pulse) is interfaced, and exactly one second when the Time Synchronization pulse (PPS pulse) is interfaced. Note that on modern GPS receivers the output latency is normally very low (usually less than 100 msec).

The same I/O port can be used to interface position and time tags.This is only possible for a certain driver at the moment, see related drivers.