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1132451Sroberto<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 2132451Sroberto 3132451Sroberto<html> 4132451Sroberto 5132451Sroberto <head> 6132451Sroberto <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> 7132451Sroberto <meta name="GENERATOR" content="Mozilla/4.01 [en] (Win95; I) [Netscape]"> 8132451Sroberto <title>Arbiter 1088A/B GPS Receiver</title> 9132451Sroberto <link href="../scripts/style.css" type="text/css" rel="stylesheet"> 10132451Sroberto </head> 11132451Sroberto 12132451Sroberto <body> 13132451Sroberto <h3>Arbiter 1088A/B GPS Receiver</h3> 14132451Sroberto <hr> 15132451Sroberto <h4>Synopsis</h4> 16132451Sroberto <p>Address: 127.127.11.<i>u</i><br> 17132451Sroberto Reference ID: <tt>GPS</tt><br> 18132451Sroberto Driver ID: <tt>GPS_ARBITER</tt><br> 19132451Sroberto Serial Port: <tt>/dev/gps<i>u</i></tt>; 9600 baud, 8-bits, no parity<br> 20132451Sroberto Features: <tt>tty_clk</tt></p> 21132451Sroberto <h4> 22132451Sroberto <p>Description</p> 23132451Sroberto </h4> 24132451Sroberto <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> 25132451Sroberto <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> 26132451Sroberto <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> 27132451Sroberto <p>Format <tt>B5</tt> (24 ASCII printing characters):</p> 28132451Sroberto <pre><cr><lf>i yy ddd hh:mm:ss.000bbb 29132451Sroberto 30132451Srobertoon-time = <cr> 31132451Srobertoi = synchronization flag (' ' = locked, '?' = unlocked) 32132451Srobertoyy = year of century 33132451Srobertoddd = day of year 34132451Srobertohh:mm:ss = hours, minutes, seconds 35132451Sroberto.000 = fraction of second (not used) 36132451Srobertobbb = tailing spaces for fill</pre> 37132451Sroberto <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> 38132451Sroberto <p>The time quality character is encoded in IEEE P1344 standard:</p> 39132451Sroberto <p>Format <tt>TQ</tt> (IEEE P1344 estimated worst-case time quality)</p> 40132451Sroberto <pre>0 clock locked, maximum accuracy 41132451SrobertoF clock failure, time not reliable 42132451Sroberto4 clock unlocked, accuracy < 1 us 43132451Sroberto5 clock unlocked, accuracy < 10 us 44132451Sroberto6 clock unlocked, accuracy < 100 us 45132451Sroberto7 clock unlocked, accuracy < 1 ms 46132451Sroberto8 clock unlocked, accuracy < 10 ms 47132451Sroberto9 clock unlocked, accuracy < 100 ms 48132451SrobertoA clock unlocked, accuracy < 1 s 49132451SrobertoB clock unlocked, accuracy < 10 s</pre> 50132451Sroberto <p>The status string is encoded as follows:</p> 51132451Sroberto <p>Format <tt>SR</tt> (25 ASCII printing characters)</p> 52132451Sroberto <pre>V=vv S=ss T=t P=pdop E=ee 53132451Sroberto 54132451Srobertovv = satellites visible 55132451Srobertoss = relative signal strength 56132451Srobertot = satellites tracked 57132451Srobertopdop = position dilution of precision (meters) 58132451Srobertoee = hardware errors</pre> 59132451Sroberto <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> 60132451Sroberto <h4>Monitor Data</h4> 61132451Sroberto <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> 62132451Sroberto <h4>Fudge Factors</h4> 63132451Sroberto <dl> 64132451Sroberto <dt><tt>time1 <i>time</i></tt> 65132451Sroberto <dd>Specifies the time offset calibration factor, in seconds and fraction, with default 0.0. 66132451Sroberto <dt><tt>time2 <i>time</i></tt> 67132451Sroberto <dd>Not used by this driver. 68132451Sroberto <dt><tt>stratum <i>number</i></tt> 69132451Sroberto <dd>Specifies the driver stratum, in decimal from 0 to 15, with default 0. 70132451Sroberto <dt><tt>refid <i>string</i></tt> 71132451Sroberto <dd>Specifies the driver reference identifier, an ASCII string from one to four characters, with default <tt>GPS</tt>. 72132451Sroberto <dt><tt>flag1 0 | 1</tt> 73132451Sroberto <dd>Not used by this driver. 74132451Sroberto <dt><tt>flag2 0 | 1</tt> 75132451Sroberto <dd>Not used by this driver. 76132451Sroberto <dt><tt>flag3 0 | 1</tt> 77132451Sroberto <dd>Not used by this driver. 78132451Sroberto <dt><tt>flag4 0 | 1</tt> 79132451Sroberto <dd>Enable verbose <tt>clockstats</tt> recording if set. 80132451Sroberto </dl> 81132451Sroberto <h4>Additional Information</h4> 82132451Sroberto <p><a href="../refclock.html">Reference Clock Drivers</a></p> 83132451Sroberto <hr> 84132451Sroberto <script type="text/javascript" language="javascript" src="../scripts/footer.txt"></script> 85132451Sroberto </body> 86132451Sroberto 87132451Sroberto</html>