154 lines
3.8 KiB
HTML
154 lines
3.8 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<HTML>
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<HEAD>
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<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-
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1">
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<META NAME="GENERATOR" CONTENT="Mozilla/4.06 [en] (X11; I; FreeBSD
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3.0-CURRENT i386) [Netscape]">
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<TITLE>Motorola Oncore GPS Receiver
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</TITLE>
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</HEAD>
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<BODY>
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<H3>
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Motorola Oncore GPS receiver</H3>
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<HR>
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<H4>
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Synopsis</H4>
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Address: 127.127.30.0
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<BR>Reference ID: <TT>GPS</TT>
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<BR>Driver ID: ONCORE
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<BR>Serial Port: <TT>/dev/cuaa0</TT>; 9600 baud, 8-bits, no parity
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<BR>PPS Port: <TT>/dev/xpps0</TT>; <TT>PPS_CAPTUREASSERT</TT>
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required, <TT>PPS_OFFSETASSERT</TT> supported.
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<H4>
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Description</H4>
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This driver supports various models of the <A
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HREF="http://www.mot.com/AECS/PNSB/products">Motorola Oncore GPS
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receivers</A>. as long as they support the <I>Motorola Binary
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Protocol</I>.
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<P>The two most interesting version of the Oncore are the "UT+"
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and the "Remote" which is a prepackaged "UT+". The evaluation kit
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can also be recommended, it interfaces to a PC straightaway, using the
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parallel port for PPS input (supported under FreeBSD), and packs the
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receiver in a nice and sturdy box.
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<BR>
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<CENTER><TABLE NOSAVE >
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<TR NOSAVE>
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<TD NOSAVE><IMG SRC="pic/oncore_utplusbig.gif" HEIGHT=124
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WIDTH=210></TD>
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<TD><IMG SRC="pic/oncore_evalbig.gif" HEIGHT=124 WIDTH=182></TD>
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<TD><IMG SRC="pic/oncore_remoteant.jpg" HEIGHT=188 WIDTH=178></TD>
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</TR>
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<TR>
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<TD>
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<CENTER>UT+ oncore</CENTER>
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</TD>
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<TD>
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<CENTER>Evaluation kit</CENTER>
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</TD>
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<TD>
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<CENTER>Oncore Remote</CENTER>
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</TD>
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</TR>
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</TABLE></CENTER>
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<P>The driver requires a standard <TT>PPS</TT> interface for the pulse-
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per-second output from the receiver. The serial data stream alone
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does not provide precision time stamps (0-50msec variance, according to
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the manual), whereas the PPS output is precise down to 50 nsec (1 sigma)
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for the UT models. <P>The driver will use the "position hold" mode if
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available, with either the receivers built-in site-survey or a similar
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algorithm implemented in this driver.
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<H4>
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Monitor Data</H4>
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The driver is quite chatty on stdout if ntpd is run with
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debugging.
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A manual will be required though.
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<H4>
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Fudge Factors</H4>
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<DL>
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<DT>
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<TT>time1 <I>time</I></TT></DT>
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<DD>
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Specifies the time offset calibration factor, in seconds and fraction,
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with default 0.0.</DD>
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<DT>
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<TT>time2 <I>time</I></TT></DT>
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<DD>
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Not used by this driver.</DD>
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<DT>
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<TT>stratum <I>number</I></TT></DT>
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<DD>
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Specifies the driver stratum, in decimal from 0 to 15, with default
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0.</DD>
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<DT>
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<TT>refid <I>string</I></TT></DT>
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<DD>
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Specifies the driver reference identifier, an ASCII string from one to
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four characters, with default <TT>GPS</TT>.</DD>
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<DT>
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<TT>flag1 0 | 1</TT></DT>
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<DD>
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Not used by this driver.</DD>
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<DT>
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<TT>flag2 0 | 1</TT></DT>
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<DD>
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Assume GPS receiver is on a mobile platform if set.</DD>
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<DT>
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<TT>flag3 0 | 1</TT></DT>
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<DD>
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Not used by this driver.</DD>
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<DT>
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<TT>flag4 0 | 1</TT></DT>
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<DD>
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Not used by this driver.</DD>
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</DL>
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<B>Additional Information</B><B></B>
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<P>The driver has been developed under FreeBSD, and may still be pretty
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FreeBSD centric. Patches are most welcome.
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<P><B>Performance</B><B></B>
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<P>Really good. With the UT+, the generated PPS pulse is
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referenced
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to UTC(GPS) with better than 50 nsec (1 sigma) accuracy. The
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limiting factor will be the timebase of the computer and the precision
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with which you can timestamp the rising flank of the
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PPS signal.
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Using FreeBSD, a FPGA based Timecounter/PPS interface
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and
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an ovenized quartz oscillator, that performance has been reproduced.
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For
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more details on this aspect: <A
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HREF="http://phk.freebsd.dk/rover.html">Sub-Microsecond
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timekeeping under FreeBSD</A>
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<HR>
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<ADDRESS>
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Poul-Henning Kamp (phk@FreeBSD.org)</ADDRESS>
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</BODY>
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</HTML>
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