19c2daa00SOllivier Robert<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 29c2daa00SOllivier Robert<html> 39c2daa00SOllivier Robert<head> 49c2daa00SOllivier Robert<meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1"> 59c2daa00SOllivier Robert<meta name="GENERATOR" content="Mozilla/4.01 [en] (Win95; I) [Netscape]"> 69c2daa00SOllivier Robert<title>Arbiter 1088A/B GPS Receiver</title> 79c2daa00SOllivier Robert<link href="scripts/style.css" type="text/css" rel="stylesheet"> 89c2daa00SOllivier Robert</head> 99c2daa00SOllivier Robert<body> 109c2daa00SOllivier Robert<h3>Arbiter 1088A/B GPS Receiver</h3> 119c2daa00SOllivier Robert<p>Author: David L. Mills (mills@udel.edu)<br> 129c2daa00SOllivier Robert Last update: 139c2daa00SOllivier Robert <!-- #BeginDate format:En2m -->11-Sep-2010 05:56<!-- #EndDate --> 149c2daa00SOllivier Robert UTC</p> 159c2daa00SOllivier Robert<hr> 169c2daa00SOllivier Robert<h4>Synopsis</h4> 179c2daa00SOllivier Robert<p>Address: 127.127.11.<i>u</i><br> 189c2daa00SOllivier Robert Reference ID: <tt>GPS</tt><br> 199c2daa00SOllivier Robert Driver ID: <tt>GPS_ARBITER</tt><br> 209c2daa00SOllivier Robert Serial Port: <tt>/dev/gps<i>u</i></tt>; 9600 baud, 8-bits, no parity<br> 219c2daa00SOllivier Robert Features: <tt>tty_clk</tt></p> 229c2daa00SOllivier Robert<h4>Description</h4> 239c2daa00SOllivier Robert<p>This driver supports the Arbiter 1088A/B Satellite Controlled Clock. The claimed accuracy of this clock is 100 ns relative to the PPS output when receiving four or more satellites.</p> 249c2daa00SOllivier Robert<p>The receiver should be configured before starting the NTP daemon, in order to establish reliable position and operating conditions. It does not initiate surveying or hold mode. For use with NTP, the daylight savings time feature should be disables (<tt>D0</tt> command) and the broadcast mode set to operate in UTC (<tt>BU</tt> command).</p> 259c2daa00SOllivier Robert<p>The timecode format supported by this driver is selected by the poll sequence <tt>B5</tt>, which initiates a line in the following format to be repeated once per second until turned off by the <tt>B0</tt> command.</p> 269c2daa00SOllivier Robert<p>Format <tt>B5</tt> (24 ASCII printing characters):</p> 279c2daa00SOllivier Robert<pre><cr><lf>i yy ddd hh:mm:ss.000bbb 289c2daa00SOllivier Robert 299c2daa00SOllivier Roberton-time = <cr> 309c2daa00SOllivier Roberti = synchronization flag (' ' = locked, '?' = unlocked) 319c2daa00SOllivier Robertyy = year of century 329c2daa00SOllivier Robertddd = day of year 339c2daa00SOllivier Roberthh:mm:ss = hours, minutes, seconds 349c2daa00SOllivier Robert.000 = fraction of second (not used) 359c2daa00SOllivier Robertbbb = tailing spaces for fill</pre> 369c2daa00SOllivier Robert<p>The alarm condition is indicated by a '?' at i, which indicates the receiver is not synchronized. In normal operation, a line consisting of the timecode followed by the time quality character (TQ) followed by the receiver status string (SR) is written to the clockstats file.</p> 379c2daa00SOllivier Robert<p>The time quality character is encoded in IEEE P1344 standard:</p> 389c2daa00SOllivier Robert<p>Format <tt>TQ</tt> (IEEE P1344 estimated worst-case time quality)</p> 399c2daa00SOllivier Robert<pre>0 clock locked, maximum accuracy 409c2daa00SOllivier RobertF clock failure, time not reliable 419c2daa00SOllivier Robert4 clock unlocked, accuracy < 1 us 429c2daa00SOllivier Robert5 clock unlocked, accuracy < 10 us 439c2daa00SOllivier Robert6 clock unlocked, accuracy < 100 us 449c2daa00SOllivier Robert7 clock unlocked, accuracy < 1 ms 459c2daa00SOllivier Robert8 clock unlocked, accuracy < 10 ms 469c2daa00SOllivier Robert9 clock unlocked, accuracy < 100 ms 479c2daa00SOllivier RobertA clock unlocked, accuracy < 1 s 489c2daa00SOllivier RobertB clock unlocked, accuracy < 10 s</pre> 499c2daa00SOllivier Robert<p>The status string is encoded as follows:</p> 509c2daa00SOllivier Robert<p>Format <tt>SR</tt> (25 ASCII printing characters)</p> 519c2daa00SOllivier Robert<pre>V=vv S=ss T=t P=pdop E=ee 529c2daa00SOllivier Robert 539c2daa00SOllivier Robertvv = satellites visible 549c2daa00SOllivier Robertss = relative signal strength 559c2daa00SOllivier Robertt = satellites tracked 569c2daa00SOllivier Robertpdop = position dilution of precision (meters) 579c2daa00SOllivier Robertee = hardware errors</pre> 589c2daa00SOllivier Robert<p>A three-stage median filter is used to reduce jitter and provide a dispersion measure. The driver makes no attempt to correct for the intrinsic jitter of the radio itself.</p> 599c2daa00SOllivier Robert<h4>Monitor Data</h4> 609c2daa00SOllivier Robert<p>When enabled by the <tt>flag4</tt> fudge flag, an additional line containing the latitude, longitude, elevation and optional deviation data is written to the <tt>clockstats</tt> file. The deviation data operates with an external pulse-per-second (PPS) input, such as a cesium oscillator or another radio clock. The PPS input should be connected to the B event channel and the radio initialized for deviation data on that channel. The deviation data consists of the mean offset and standard deviation of the external PPS signal relative the GPS signal, both in microseconds over the last 16 seconds.</p> 619c2daa00SOllivier Robert<h4>Fudge Factors</h4> 629c2daa00SOllivier Robert<dl> 639c2daa00SOllivier Robert <dt><tt>time1 <i>time</i></tt></dt> 649c2daa00SOllivier Robert <dd>Specifies the time offset calibration factor, in seconds and fraction, with default 0.0.</dd> 659c2daa00SOllivier Robert <dt><tt>time2 <i>time</i></tt></dt> 669c2daa00SOllivier Robert <dd>Not used by this driver.</dd> 679c2daa00SOllivier Robert <dt><tt>stratum <i>number</i></tt></dt> 689c2daa00SOllivier Robert <dd>Specifies the driver stratum, in decimal from 0 to 15, with default 0.</dd> 699c2daa00SOllivier Robert <dt><tt>refid <i>string</i></tt></dt> 709c2daa00SOllivier Robert <dd>Specifies the driver reference identifier, an ASCII string from one to four characters, with default <tt>GPS</tt>.</dd> 719c2daa00SOllivier Robert <dt><tt>flag1 0 | 1</tt></dt> 729c2daa00SOllivier Robert <dd>Not used by this driver.</dd> 739c2daa00SOllivier Robert <dt><tt>flag2 0 | 1</tt></dt> 749c2daa00SOllivier Robert <dd>Not used by this driver.</dd> 759c2daa00SOllivier Robert <dt><tt>flag3 0 | 1</tt></dt> 769c2daa00SOllivier Robert <dd>Not used by this driver.</dd> 779c2daa00SOllivier Robert <dt><tt>flag4 0 | 1</tt></dt> 789c2daa00SOllivier Robert <dd>Enable verbose <tt>clockstats</tt> recording if set.</dd> 799c2daa00SOllivier Robert</dl> 809c2daa00SOllivier Robert<h4>Additional Information</h4> 819c2daa00SOllivier Robert<p><a href="../refclock.html">Reference Clock Drivers</a></p> 829c2daa00SOllivier Robert<hr> 839c2daa00SOllivier Robert<script type="text/javascript" language="javascript" src="scripts/footer.txt"></script> 849c2daa00SOllivier Robert</body> 859c2daa00SOllivier Robert</html> 869c2daa00SOllivier Robert