19c2daa00SOllivier Robert<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 29c2daa00SOllivier Robert 39c2daa00SOllivier Robert<html> 49c2daa00SOllivier Robert 59c2daa00SOllivier Robert <head> 69c2daa00SOllivier Robert <meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1"> 7*2b15cb3dSCy Schubert <title>TrueTime GPS/GOES/OMEGA/WWV Receivers</title> 8ea906c41SOllivier Robert <link href="scripts/style.css" type="text/css" rel="stylesheet"> 99c2daa00SOllivier Robert </head> 109c2daa00SOllivier Robert 119c2daa00SOllivier Robert <body> 12*2b15cb3dSCy Schubert <h3>TrueTime GPS/GOES/OMEGA/WWV Receivers</h3> 139c2daa00SOllivier Robert <hr> 149c2daa00SOllivier Robert <h4>Synopsis</h4> 159c2daa00SOllivier Robert Address: 127.127.5.<i>u</i><br> 16*2b15cb3dSCy Schubert Reference ID: <tt>GPS, OMEGA, GOES, WWV</tt><br> 179c2daa00SOllivier Robert Driver ID: <tt>TRUETIME</tt><br> 189c2daa00SOllivier Robert Serial Port: <tt>/dev/true<i>u</i></tt>; 9600 baud, 8-bits, no parity<br> 199c2daa00SOllivier Robert Features: <tt>tty_clk</tt> 209c2daa00SOllivier Robert <h4>Description</h4> 21*2b15cb3dSCy Schubert <p>This driver supports several models models of Kinemetrics/TrueTime timing receivers, including 468-DC MK III GOES Synchronized Clock, GPS- DC MK III and GPS/TM-TMD GPS Synchronized Clock, XL-DC (a 151-602-210, reported by the driver as a GPS/TM-TMD), GPS-800 TCU (an 805-957 with the RS232 Talker/Listener module), OM-DC OMEGA Synchronized Clock, the TL-3 WWV receiver, and very likely others in the same model families that use the same timecode formats.</p> 229c2daa00SOllivier Robert <p>Most of this code is originally from refclock_wwvb.c with thanks. It has been so mangled that wwvb is not a recognizable ancestor.</p> 23*2b15cb3dSCy Schubert <p>Timcode format: <tt>ADDD:HH:MM:SSQCL</tt><br> 24*2b15cb3dSCy SchubertA - control A (this is stripped before we see it) Q - Quality indication (see below) C - Carriage return L - Line feed</p><br> 25*2b15cb3dSCy SchubertQuality codes indicate possible error of: 269c2daa00SOllivier Robert <dl> 279c2daa00SOllivier Robert <dt>468-DC GOES Receiver<br> 289c2daa00SOllivier Robert GPS-TM/TMD Receiver 299c2daa00SOllivier Robert <dd>? +/- 500 milliseconds # +/- 50 milliseconds<br> 309c2daa00SOllivier Robert * +/- 5 milliseconds . +/- 1 millisecond<br> 319c2daa00SOllivier Robert space less than 1 millisecond 329c2daa00SOllivier Robert <dt>OM-DC OMEGA Receiver: 339c2daa00SOllivier Robert <dd>> +/- 5 seconds<br> 349c2daa00SOllivier Robert ? +/- 500 milliseconds # +/- 50 milliseconds<br> 359c2daa00SOllivier Robert * +/- 5 milliseconds . +/- 1 millisecond<br> 369c2daa00SOllivier Robert A-H less than 1 millisecond. Character indicates which station is being received as follows<br> 379c2daa00SOllivier Robert A = Norway, B = Liberia, C = Hawaii, D = North Dakota, E = La Reunion, F = Argentina, G = Australia, H = Japan<br> 389c2daa00SOllivier Robert The carriage return start bit begins on 0 seconds and extends to 1 bit time. 39*2b15cb3dSCy Schubert <dt>TL-3 WWV Receiver: 40*2b15cb3dSCy Schubert <dd>? receiver is unlocked<br> 41*2b15cb3dSCy Schubert <dd>space +/- 5 milliseconds<br> 429c2daa00SOllivier Robert </dl> 439c2daa00SOllivier Robert <h4>Notes on 468-DC and OMEGA receiver:</h4> 449c2daa00SOllivier Robert <p>Send the clock a <tt>R</tt> or <tt>C</tt> and once per second a timestamp will appear. Send a <tt>R</tt> to get the satellite position once (GOES only).</p> 459c2daa00SOllivier Robert <h4>Notes on the 468-DC receiver:</h4> 469c2daa00SOllivier Robert <p>Since the old east/west satellite locations are only historical, you can't set your clock propagation delay settings correctly and still use automatic mode. The manual says to use a compromise when setting the switches. This results in significant errors. The solution; use fudge time1 and time2 to incorporate corrections. If your clock is set for 50 and it should be 58 for using the west and 46 for using the east, use the line</p> 479c2daa00SOllivier Robert <p><tt>fudge 127.127.5.0 time1 +0.008 time2 -0.004</tt></p> 489c2daa00SOllivier Robert <p>This corrects the 4 milliseconds advance and 8 milliseconds retard needed. The software will ask the clock which satellite it sees.</p> 499c2daa00SOllivier Robert <p>The PCL720 from PC Labs has an Intel 8253 look-alike, as well as a bunch of TTL input and output pins, all brought out to the back panel. If you wire a PPS signal (such as the TTL PPS coming out of a GOES or other Kinemetrics/Truetime clock) to the 8253's GATE0, and then also wire the 8253's OUT0 to the PCL720's INPUT3.BIT0, then we can read CTR0 to get the number of microseconds since the last PPS upward edge, mediated by reading OUT0 to find out if the counter has wrapped around (this happens if more than 65535us (65ms) elapses between the PPS event and our being called.)</p> 50*2b15cb3dSCy Schubert <h4>Notes on the TL-3 receiver:</h4> 51*2b15cb3dSCy Schubert <p>The mini-DIN RS-232 port uses the Apple pinout.<br> 52*2b15cb3dSCy Schubert Send the clock ST1 to turn on continuous (1/sec) timecodes. 53*2b15cb3dSCy SchubertYou can also enable "mode C" via the front panel. ST0 turns off this mode.<br> 54*2b15cb3dSCy SchubertQV will return the firmware revision (and is useful in identifying this clock.)<br> 55*2b15cb3dSCy SchubertQW will return its weekly signal log, useful if you're testing antennas. You may wish to turn the loss interval down from 4h (04) to 1h (01), so the receiver declares itself unlocked sooner. When in holdover, drift can be on the order of 10 ms/hr since there is no high quality reference oscillator.</p> 569c2daa00SOllivier Robert <h4>Monitor Data</h4> 579c2daa00SOllivier Robert <p>When enabled by the <tt>flag4</tt> fudge flag, every received timecode is written as-is to the <tt>clockstats</tt> file.</p> 589c2daa00SOllivier Robert <h4>Fudge Factors</h4> 599c2daa00SOllivier Robert <dl> 609c2daa00SOllivier Robert <dt><tt>time1 <i>time</i></tt> 619c2daa00SOllivier Robert <dd>Specifies the time offset calibration factor, in seconds and fraction, to be used for the West satellite, with default 0.0. 629c2daa00SOllivier Robert <dt><tt>time2 <i>time</i></tt> 639c2daa00SOllivier Robert <dd>. Specifies the time offset calibration factor, in seconds and fraction, to be used for the East satellite, with default 0.0. 649c2daa00SOllivier Robert <dt><tt>stratum <i>number</i></tt> 659c2daa00SOllivier Robert <dd>Specifies the driver stratum, in decimal from 0 to 15, with default 0. 669c2daa00SOllivier Robert <dt><tt>refid <i>string</i></tt> 679c2daa00SOllivier Robert <dd>Specifies the driver reference identifier, an ASCII string from one to four characters, with default <tt>TRUE</tt>. 689c2daa00SOllivier Robert <dt><tt>flag1 0 | 1</tt> 699c2daa00SOllivier Robert <dd>Silence the clock side of ntpd, just reading the clock without trying to write to it. 709c2daa00SOllivier Robert <dt><tt>flag2 0 | 1</tt> 719c2daa00SOllivier Robert <dd>Generate a debug file /tmp/true%d. 729c2daa00SOllivier Robert <dt><tt>flag3 0 | 1</tt> 739c2daa00SOllivier Robert <dd>Not used by this driver. 749c2daa00SOllivier Robert <dt><tt>flag4 0 | 1</tt> 75*2b15cb3dSCy Schubert <dd>Enable verbose <tt>clockstats</tt> recording if set. 769c2daa00SOllivier Robert </dl> 779c2daa00SOllivier Robert <h4>Additional Information</h4> 78ea906c41SOllivier Robert <p><a href="../refclock.html">Reference Clock Drivers</a></p> 799c2daa00SOllivier Robert <hr> 80ea906c41SOllivier Robert <script type="text/javascript" language="javascript" src="scripts/footer.txt"></script> 819c2daa00SOllivier Robert </body> 829c2daa00SOllivier Robert 839c2daa00SOllivier Robert</html> 84