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Re: [gpsd-dev] RFC - drop "tag" fields from the public interface

From: Hal Murray
Subject: Re: [gpsd-dev] RFC - drop "tag" fields from the public interface
Date: Sun, 24 Aug 2014 01:01:31 -0700

address@hidden said:
> Time is collected at the same point in the cycle every time. What sentence
> that is varies by GPS type but is always the same sentence type for any one
> GPS.

> There's a cycle detector in the code that watches timestamped sentences
> (ignoring others) looking for where the stamp changes from T to T+1.  It
> then marks the sentence type just *before* the T+1 sentence as the
> end-of-cycle type.  Thereafter, reports (including time) are issued on
> end-of-cycle.

> The uBlox 4 LEA is a representative example.  Each cycle it ships $GPZDA,
> $GPRMC, $GPVTG, $GPGGA, $GPGSA, $GPGSV, $GPGLL. Timestamps occur in ZDA RMC
> GGA GLL; the timestamp is incremented on ZDA.

> In this case, gspd notices that the timestamp is incremented on ZDA, which
> comes after GLL.  GLL is marked as end of cycle, reports are issued on every
> GLL using info accumulated from  ZDA RMC GGA GLL, and GLL fills the tag
> field of the resulting TPV.


OK, if that's how it works, I agree that the tag isn't useful.

One quirk to consider.  I've seen some units that do something like send GSV 
every 5th second.


These are my opinions.  I hate spam.

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