driver20.html revision 132451
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/4.76 [en] (X11; U; Linux 2.2.16-22 i586) [Netscape]"> 8132451Sroberto <title>Generic NMEA GPS Receiver</title> 9132451Sroberto <link href="../scripts/style.css" type="text/css" rel="stylesheet"> 10132451Sroberto </head> 11132451Sroberto 12132451Sroberto <body> 13132451Sroberto <h3>Generic NMEA GPS Receiver</h3> 14132451Sroberto <hr> 15132451Sroberto <h4>Synopsis</h4> 16132451Sroberto <p>Address: 127.127.20.<i>u</i><br> 17132451Sroberto Reference ID: <tt>GPS</tt><br> 18132451Sroberto Driver ID: <tt>GPS_NMEA</tt><br> 19132451Sroberto Serial Port: <tt>/dev/gps<i>u</i></tt>; 4800 baud, 8-bits, no parity<br> 20132451Sroberto Features: <tt>tty_clk</tt></p> 21132451Sroberto <h4>Description</h4> 22132451Sroberto <p>This driver supports GPS receivers with the <tt>$GPRMC</tt> NMEA output string by default. Alternately the <tt>$GPGGA</tt> or <tt>$GPGLL </tt>may be selected.</p> 23132451Sroberto <p>The driver expects the receiver to be set up to transmit a <tt>$GPRMC</tt> message every second.</p> 24132451Sroberto <p>The accuracy depend on the receiver used. Inexpesive GPS models are available with a claimed PPS signal accuracy of 1 <font face="Symbol">m</font>s or better relative to the broadcast signal. However, in most cases the actual accuracy is limited by the precision of the timecode and the latencies of the serial interface and operating system.</p> 25132451Sroberto <p>If the Operating System supports the PPSAPI, RFC-2783, it will be used.<br> 26132451Sroberto </p> 27132451Sroberto <p>The various GPS sentences that this driver recognises look like this:<br> 28132451Sroberto (others quietly ignored)</p> 29132451Sroberto <pre><tt>$GPRMC,POS_UTC,POS_STAT,LAT,LAT_REF,LON,LON_REF,SPD,HDG,DATE,MAG_VAR,MAG_REF*CC<cr><lf> 30132451Sroberto$GPGLL,LAT,LAT_REF,LONG,LONG_REF,POS_UTC,POS_STAT*CC<cr><lf> 31132451Sroberto$GPGGA,POS_UTC,LAT,LAT_REF,LONG,LONG_REF,FIX_MODE,SAT_USED,HDOP,ALT,ALT_UNIT,GEO,G_UNIT,D_AGE,D_REF*CC<cr><lf> 32132451Sroberto 33132451Sroberto POS_UTC - UTC of position. Hours, minutes and seconds [fraction (opt.)]. (hhmmss[.fff]) 34132451Sroberto POS_STAT - Position status. (A = Data valid, V = Data invalid) 35132451Sroberto LAT - Latitude (llll.ll) 36132451Sroberto LAT_REF - Latitude direction. (N = North, S = South) 37132451Sroberto LON - Longitude (yyyyy.yy) 38132451Sroberto LON_REF - Longitude direction (E = East, W = West) 39132451Sroberto SPD - Speed over ground. (knots) (x.x) 40132451Sroberto HDG - Heading/track made good (degrees True) (x.x) 41132451Sroberto DATE - Date (ddmmyy) 42132451Sroberto MAG_VAR - Magnetic variation (degrees) (x.x) 43132451Sroberto MAG_REF - Magnetic variation (E = East, W = West) 44132451Sroberto FIX_MODE - Position Fix Mode ( 0 = Invalid, >0 = Valid) 45132451Sroberto SAT_USED - Number Satellites used in solution 46132451Sroberto HDOP - Horizontal Dilution of Precision 47132451Sroberto ALT - Antenna Altitude 48132451Sroberto ALT_UNIT - Altitude Units (Metres/Feet) 49132451Sroberto GEO - Geoid/Elipsoid separation 50132451Sroberto G_UNIT - Geoid units (M/F) 51132451Sroberto D_AGE - Age of last DGPS Fix 52132451Sroberto D_REF - Reference ID of DGPS station 53132451Sroberto CC - Checksum (optional) 54132451Sroberto <cr><lf> - Sentence terminator.</tt></pre> 55132451Sroberto Alternate GPS sentences (other than <tt>$GPRMC</tt> - the default) may be enabled by setting the relevent bits of 'mode' in the server configuration line<br> 56132451Sroberto * server 127.127.20.x mode X<br> 57132451Sroberto bit 0 - enables RMC ( value = 1)<br> 58132451Sroberto bit 1 - enables GGA ( value = 2)<br> 59132451Sroberto bit 2 - enables GLL ( value = 4)<br> 60132451Sroberto multiple sentences may be selected<br> 61132451Sroberto <p>The driver will send a <tt>$PMOTG,RMC,0000*1D<cr><lf></tt> message each time a <tt>$GPRMC</tt> string is needed. This is not needed on most GPS receivers because they automatically send the <tt>$GPRMC</tt> string every second and will only work on GPS receivers that understand the <tt>$PMOTG</tt> string. Others will just ignore it.</p> 62132451Sroberto <h4>Setting up the Garmin GPS-25XL</h4> 63132451Sroberto Switch off all output with by sending it the following string. 64132451Sroberto <pre>"$PGRMO,,2<cr><lf>"</pre> 65132451Sroberto <p>Now switch only $GPRMC on by sending it the following string.</p> 66132451Sroberto <pre>"$PGRMO,GPRMC,1<cr><lf>"</pre> 67132451Sroberto <p>On some systems the PPS signal isn't switched on by default. It can be switched on by sending the following string.</p> 68132451Sroberto <pre>"$PGRMC,,,,,,,,,,,,2<cr><lf>"</pre> 69132451Sroberto <h4>Monitor Data</h4> 70132451Sroberto <p>The GPS sentence(s) that is used is written to the clockstats file.</p> 71132451Sroberto <h4>Fudge Factors</h4> 72132451Sroberto <dl> 73132451Sroberto <dt><tt>time1 <i>time</i></tt> 74132451Sroberto <dd>Specifies the time offset calibration factor, in seconds and fraction, with default 0.0. 75132451Sroberto <dt><tt>time2 <i>time</i></tt> 76132451Sroberto <dd>Not used by this driver. 77132451Sroberto <dt><tt>stratum <i>number</i></tt> 78132451Sroberto <dd>Specifies the driver stratum, in decimal from 0 to 15, with default 0. 79132451Sroberto <dt><tt>refid <i>string</i></tt> 80132451Sroberto <dd>Specifies the driver reference identifier, an ASCII string from one to four characters, with default <tt>GPS</tt>. 81132451Sroberto <dt><tt>flag1 0 | 1</tt> 82132451Sroberto <dd>Not used by this driver. 83132451Sroberto <dt><tt>flag2 0 | 1</tt> 84132451Sroberto <dd>Specifies the PPS signal on-time edge: 0 for assert (default), 1 for clear. 85132451Sroberto <dt><tt>flag3 0 | 1</tt> 86132451Sroberto <dd>Controls the kernel PPS discipline: 0 for disable (default), 1 for enable. 87132451Sroberto <dt><tt>flag4 0 | 1</tt> 88132451Sroberto <dd>Not used by this driver. 89132451Sroberto </dl> 90132451Sroberto <p>Additional Information</p> 91132451Sroberto <p><a href="../refclock.html">Reference Clock Drivers</a></p> 92132451Sroberto <hr> 93132451Sroberto <script type="text/javascript" language="javascript" src="../scripts/footer.txt"></script> 94132451Sroberto </body> 95132451Sroberto 96132451Sroberto</html>