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Re: [gpsd-dev] Modifying (severly) hardware.html


From: Eric S. Raymond
Subject: Re: [gpsd-dev] Modifying (severly) hardware.html
Date: Mon, 13 Apr 2015 15:18:28 -0400
User-agent: Mutt/1.5.23 (2014-03-12)

Hal Murray <address@hidden>:
> address@hidden said:
> > The current: http://www.catb.org/gpsd/hardware.html is good, if you have a
> > model in mind.  Not so good if you are asking "What should I buy that is
> > supported?" 
> 
> If that's the question, I think the format of the answer would be a short 
> list of known to work well devices and/or devices to beware of, probably 
> focusing on the chips.
> 
> This is what I would say if somebody asked me "What should I get?"
> 
> SiRF 3 is good but poor for timing without PPS.  (100 ms wander)
> 
> SiRF 4 doesn't work well in binary mode.  Is it OK in NMEA mode?
> 
> The uBlox chips are good.  (I think.)
> 
> The Garmin 18x is OK.  Same PPS/wander problem as SiRF.
> 
> The xxx chip on the Sure board is good.  (Needs soldering to get PPS.)
> 
> The ???? chip on the Adafruit GPS hat works OK.
> 
> 
> PPS over USB works and is often much better than no PPS but not as good as 
> PPS via a real serial port or GPIO.  (Has anybody tried a printer port 
> recently?)
> 
> Older devices are much less sensitive.  Modern devices often work well enough 
> indoors where older chips frequently drop out.

That's a good start.  I would modify as follows:

The SiRF IV has very poor weak-signal performance. I would not
recommend it unless you are certain you will always have a clear
skyview.

The uBlox chips are *excellent*.  If there were a readily available 
consumer-grade uBlox-based device I would recommend nothing else.

(The Sure board uses an engine called a SKG16B which is otherwise unattested.
The Adafruit hat has a Venus 6 in it.)

In 2015, sadly, your best bat for a packaged GPS is to find a remaindered
SiRF-III.  But you almost certainly won't get PPS out of it.
-- 
                <a href="http://www.catb.org/~esr/";>Eric S. Raymond</a>



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