From: "Eric S. Raymond" <esr@thyrsus.com>
To: "Ron Frazier (NTP)" <timekeepingntplist@techstarship.com>
Cc: thumbgps-devel@lists.bufferbloat.net
Subject: Re: [Thumbgps-devel] [gpsd-dev] PPS over USB
Date: Sun, 6 May 2012 18:09:25 -0400 [thread overview]
Message-ID: <20120506220925.GF14699@thyrsus.com> (raw)
In-Reply-To: <4FA13959.9050405@techstarship.com>
Ron Frazier (NTP) <timekeepingntplist@techstarship.com>:
> Just wondering. On the USB + PPS + PL2303 concept, has the long
> term variation that has been observed in NMEA data in other similar
> units without PPS been accounted for?
No. Hal Murray and I studied this extensively and were unable to
get a handle on the cause.
> I have personally observed a
> variation in NMEA data on my Globalsat Sirf III USB device of up to
> +/- 70 ms over several days. Will having the PPS coming though USB
> solve that problem?
Yes. The measured jitter of 1PPS over PL2303 USB is 0.5 milliseconds.
--
<a href="http://www.catb.org/~esr/">Eric S. Raymond</a>
next prev parent reply other threads:[~2012-05-06 22:09 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20120501151435.4a6a5373.gem@rellim.com>
2012-05-01 22:16 ` [Thumbgps-devel] Fwd: " Dave Taht
2012-05-02 1:40 ` [Thumbgps-devel] " Dave Taht
2012-05-02 3:07 ` Jim Thompson
2012-05-02 3:33 ` Eric S. Raymond
2012-05-02 7:58 ` Hal Murray
2012-05-06 21:28 ` Eric S. Raymond
2012-05-02 11:09 ` tz
[not found] ` <20120502131310.7dd7f799.gem@rellim.com>
2012-05-02 20:33 ` tz
2012-05-02 21:19 ` Hal Murray
2012-05-02 21:43 ` tz
2012-05-02 13:40 ` Ron Frazier (NTP)
[not found] ` <20120502124227.28ef9fa6.gem@rellim.com>
2012-05-03 4:07 ` Ron Frazier (NTP)
2012-05-06 22:09 ` Eric S. Raymond [this message]
[not found] ` <4FA43068.2080606@wildgooses.com>
[not found] ` <20120504160455.4514ac26.gem@rellim.com>
[not found] ` <20120506214138.GB14699@thyrsus.com>
[not found] ` <4FA6F396.70307@tmsw.no>
[not found] ` <4FA7BDF1.7030708@wildgooses.com>
[not found] ` <4FA7CFB2.9080807@tmsw.no>
[not found] ` <4FA7E197.9010902@wildgooses.com>
[not found] ` <20120507205843.GA21259@thyrsus.com>
2012-05-07 21:14 ` Dave Taht
2012-05-07 21:52 ` Eric S. Raymond
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