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1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
2<HTML>
3<HEAD>
4   <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-
51">
6   <META NAME="GENERATOR" CONTENT="Mozilla/4.06 [en] (X11; I; FreeBSD
73.0-CURRENT i386) [Netscape]">
8   <TITLE>Motorola Oncore GPS Receiver
9</TITLE>
10</HEAD>
11<BODY>
12
13<H3>
14Motorola Oncore GPS receiver</H3>
15
16<HR>
17<H4>
18Synopsis</H4>
19
20Address: 127.127.30.<i>u</i><BR>
21Reference ID: <TT>GPS</TT><BR>
22Driver ID: ONCORE<BR>
23Serial Port: <TT>/dev/oncore.serial.</TT><i>u</i>; &nbsp;9600 baud, 8-bits,
24no parity.<BR>
25PPS Port: <TT>/dev/oncore.pps.</TT><i>u</i>;&nbsp; <TT>PPS_CAPTUREASSERT</TT>
26required,&nbsp; <TT>PPS_OFFSETASSERT</TT> supported.<BR>
27Configuration File: <TT>/etc/ntp.oncore<TT><i>u</i> or,
28<TT>/etc/ntp.oncore.<TT><i>u</i>, or <TT>/etc/ntp.oncore<TT>.
29<H4>
30Description</H4>
31This driver supports most models of the
32<A HREF="http://www.mot.com/AECS/PNSB/products">Motorola Oncore GPS receivers</A>
33(Basic, PVT6, VP, UT, UT+, GT, GT+, SL, M12),
34as long as they support the <I>Motorola Binary Protocol</I>.
35
36<P>The three most interesting versions of the Oncore are the VP,
37the UT+, and the "Remote" which is a prepackaged UT+.
38The VP is no longer available.
39The Motorola evaluation kit
40can also be recommended, it interfaces to a PC straightaway, using the
41serial (DCD) or parallel port for PPS input and packs the
42receiver in a nice and sturdy box.
43Two less expensive interface kits are available from
44<A HREF="http://www.tapr.org">TAPR</A>.
45
46<BR>&nbsp;
47<CENTER><TABLE NOSAVE >
48<TR NOSAVE>
49<TD NOSAVE><IMG SRC="pic/oncore_utplusbig.gif" HEIGHT=124
50WIDTH=210></TD>
51
52<TD><IMG SRC="pic/oncore_evalbig.gif" HEIGHT=124 WIDTH=182></TD>
53
54<TD><IMG SRC="pic/oncore_remoteant.jpg" HEIGHT=188 WIDTH=178></TD>
55</TR>
56
57<TR>
58<TD>
59<CENTER>UT+ oncore</CENTER>
60</TD>
61
62<TD>
63<CENTER>Evaluation kit</CENTER>
64</TD>
65
66<TD>
67<CENTER>Oncore Remote</CENTER>
68</TD>
69</TR>
70</TABLE></CENTER>
71
72<P>The driver requires a standard <TT>PPS</TT> interface for the
73pulse-per-second output from the receiver.&nbsp; The serial data stream alone
74does not provide precision time stamps (0-50msec variance, according to
75the manual), whereas the PPS output is precise down to 50 nsec (1 sigma)
76for the VP/UT models.
77If you do not have the PPS signal available, then you should probably be using
78the NMEA driver rather than the Oncore driver.
79
80<P>The driver will use the "position hold" mode with
81user provided coordinates,
82the receivers built-in site-survey,
83or a similar algorithm implemented in this driver to determine the antenna position.
84<H4>
85Monitor Data</H4>
86The driver always puts a lot of useful information on the clockstats file,
87and when run with debugging can be quite chatty on stdout.
88When first starting to use the driver you should definitely review the information
89written to the clockstats file to verify that the driver is running correctly.
90<P>
91In addition, on platforms supporting Shared Memory, all of the messages
92received from the Oncore receiver are made available in shared memory for
93use by other programs.
94See the <A HREF=Oncore-SHMEM.htm> Oncore-SHMEM </A> manual page for
95information on how to use this option.
96For either debugging or using the SHMEM option, an Oncore Reference Manual
97for the specific receiver in use will be required.
98<H4>
99Fudge Factors</H4>
100
101<DL>
102<DT>
103<TT>time1 <I>time</I></TT></DT>
104
105<DD>
106Specifies the time offset calibration factor, in seconds and fraction,
107with default 0.0.</DD>
108
109<DT>
110<TT>time2 <I>time</I></TT></DT>
111
112<DD>
113Not used by this driver.</DD>
114
115<DT>
116<TT>stratum <I>number</I></TT></DT>
117
118<DD>
119Specifies the driver stratum, in decimal from 0 to 15, with default
1200.</DD>
121
122<DT>
123<TT>refid <I>string</I></TT></DT>
124
125<DD>
126Specifies the driver reference identifier, an ASCII string from one to
127four characters, with default <TT>GPS</TT>.</DD>
128
129<DT>
130<TT>flag1 0 | 1</TT></DT>
131
132<DD>
133Not used by this driver.</DD>
134
135<DT>
136<TT>flag2 0 | 1</TT></DT>
137
138<DD>
139Not used by this driver.</DD>
140
141<DT>
142<TT>flag3 0 | 1</TT></DT>
143
144<DD>
145Not used by this driver.</DD>
146
147<DT>
148<TT>flag4 0 | 1</TT></DT>
149
150<DD>
151Not used by this driver.</DD>
152</DL>
153<B>Additional Information</B>
154<P>The driver was initially developed on FreeBSD, and has since been tested
155on Linux, SunOS and Solaris.
156<P><B>Configuration</B>
157<P>There is a driver specific configuration file <TT>/etc/ntp.oncore</TT>
158that contains information on the startup mode, the location of the GPS
159receiver, an offset of the PPS signal from zero, and the cable delay.
160The offset shifts the PPS signal to avoid interrupt pileups `on' the second,
161and adjust the timestamp accordingly.
162See the driver source for information on this file.
163The default with no file is: no delay, no offset, and a site survey is done
164to get the location of the gps receiver.
165
166<P>The <TT>/etc/ntp.conf</TT> file will need a line of the form<BR>
167&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
168<TT> pps /dev/oncore.pps.0 [ assert/clear ] hardpps</TT><BR>
169if you want the oncore driver to control the kernel PLL.
170For more information, see the  <A HREF=clockopt.htm>Reference Clock
171Options</A> page.
172
173<P><B>Performance</B>
174<P>Really good.&nbsp; With the VP/UT+, the generated PPS pulse is referenced
175to UTC(GPS)&nbsp;with better than 50 nsec (1 sigma) accuracy.&nbsp; The
176limiting factor will be the timebase of the computer and the precision
177with which you can timestamp the rising flank of the
178PPS&nbsp;signal.&nbsp;
179Using FreeBSD, a FPGA&nbsp;based Timecounter/PPS&nbsp;interface,
180and an ovenized quartz oscillator, that performance has been reproduced.
181&nbsp;For more details on this aspect:&nbsp; <A
182HREF="http://phk.freebsd.dk/rover.html">Sub-Microsecond
183timekeeping under FreeBSD</A>.
184<HR>
185<ADDRESS>
186Poul-Henning Kamp (phk@FreeBSD.org),
187Reg Clemens (reg@dwf.com)
188</ADDRESS>
189</BODY>
190</HTML>
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