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diff --git a/html/driver20.htm b/html/driver20.htm new file mode 100644 index 0000000..6d1126b --- /dev/null +++ b/html/driver20.htm @@ -0,0 +1,161 @@ +<!doctype html public "-//w3c//dtd html 4.0 transitional//en"> +<html> +<head> + <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> + <meta name="GENERATOR" content="Mozilla/4.76 [en] (X11; U; Linux 2.2.16-22 i586) [Netscape]"> + <title>Generic NMEA GPS Receiver +</title> +</head> +<body> + +<h3> +Generic NMEA GPS Receiver</h3> + +<hr> +<h4> +Synopsis</h4> +Address: 127.127.20.<i>u</i> +<br>Reference ID: <tt>GPS</tt> +<br>Driver ID: <tt>GPS_NMEA</tt> +<br>Serial Port: <tt>/dev/gps<i>u</i></tt>; 4800 baud, 8-bits, no parity +<br>Features: <tt>tty_clk</tt> +<h4> +Description</h4> +This driver supports GPS receivers with the <tt>$GPRMC</tt> NMEA output +string by default. Alternately the <tt>$GPGGA</tt> or <tt>$GPGLL +</tt>may +be selected. +<br>The driver expects the receiver to be set up to transmit a <tt>$GPRMC</tt> +message every second. +<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>If the Operating System supports the PPSAPI, RFC-2783, it will be used. +<br> +<p>The various GPS sentences that this driver recognises look like this: +<br>(others quietly ignored) +<pre><tt>$GPRMC,POS_UTC,POS_STAT,LAT,LAT_REF,LON,LON_REF,SPD,HDG,DATE,MAG_VAR,MAG_REF*CC<cr><lf> +$GPGLL,LAT,LAT_REF,LONG,LONG_REF,POS_UTC,POS_STAT*CC<cr><lf> +$GPGGA,POS_UTC,LAT,LAT_REF,LONG,LONG_REF,FIX_MODE,SAT_USED,HDOP,ALT,ALT_UNIT,GEO,G_UNIT,D_AGE,D_REF*CC<cr><lf> + + POS_UTC - UTC of position. Hours, minutes and seconds [fraction (opt.)]. (hhmmss[.fff]) + POS_STAT - Position status. (A = Data valid, V = Data invalid) + LAT - Latitude (llll.ll) + LAT_REF - Latitude direction. (N = North, S = South) + LON - Longitude (yyyyy.yy) + LON_REF - Longitude direction (E = East, W = West) + SPD - Speed over ground. (knots) (x.x) + HDG - Heading/track made good (degrees True) (x.x) + DATE - Date (ddmmyy) + MAG_VAR - Magnetic variation (degrees) (x.x) + MAG_REF - Magnetic variation (E = East, W = West) + FIX_MODE - Position Fix Mode ( 0 = Invalid, >0 = Valid) + SAT_USED - Number Satellites used in solution + HDOP - Horizontal Dilution of Precision + ALT - Antenna Altitude + ALT_UNIT - Altitude Units (Metres/Feet) + GEO - Geoid/Elipsoid separation + G_UNIT - Geoid units (M/F) + D_AGE - Age of last DGPS Fix + D_REF - Reference ID of DGPS station + CC - Checksum (optional) + <cr><lf> - Sentence terminator.</tt></pre> +Alternate GPS sentences (other than <tt>$GPRMC</tt> - the default) may +be enabled by setting the relevent bits of 'mode' in the server configuration +line +<br> * server 127.127.20.x mode X +<br> bit 0 - enables RMC ( value = +1) +<br> bit 1 - enables GGA ( value = +2) +<br> bit 2 - enables GLL +( value = 4) +<br>multiple sentences may be selected +<br> +<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. +<h4> +Setting up the Garmin GPS-25XL</h4> +Switch off all output with by sending it the following string. +<pre>"$PGRMO,,2<cr><lf>"</pre> +Now switch only $GPRMC on by sending it the following string. +<pre>"$PGRMO,GPRMC,1<cr><lf>"</pre> +On some systems the PPS signal isn't switched on by default. It can be +switched on by sending the following string. +<pre>"$PGRMC,,,,,,,,,,,,2<cr><lf>"</pre> + +<h4> +Monitor Data</h4> +The GPS sentence(s) that is used is written to the clockstats file. +<h4> +Fudge Factors</h4> + +<dl> +<dt> +<tt>time1 <i>time</i></tt></dt> + +<dd> +Specifies the time offset calibration factor, in seconds and fraction, +with default 0.0.</dd> + +<dt> +<tt>time2 <i>time</i></tt></dt> + +<dd> +Not used by this driver.</dd> + +<dt> +<tt>stratum <i>number</i></tt></dt> + +<dd> +Specifies the driver stratum, in decimal from 0 to 15, with default 0.</dd> + +<dt> +<tt>refid <i>string</i></tt></dt> + +<dd> +Specifies the driver reference identifier, an ASCII string from one to +four characters, with default <tt>GPS</tt>.</dd> + +<dt> +<tt>flag1 0 | 1</tt></dt> + +<dd> +Not used by this driver.</dd> + +<dt> +<tt>flag2 0 | 1</tt></dt> + +<dd> +Specifies the PPS signal on-time edge: 0 for assert (default), 1 for clear.</dd> + +<dt> +<tt>flag3 0 | 1</tt></dt> + +<dd> +Controls the kernel PPS discipline: 0 for disable (default), 1 for enable.</dd> + +<dt> +<tt>flag4 0 | 1</tt></dt> + +<dd> +Not used by this driver.</dd> + +<br> +<p> +<br> +<br> +<p>Additional Information +<p><a href="refclock.htm">Reference Clock Drivers</a></dl> + +<hr> +<address> +David L. Mills (mills@udel.edu)</address> + +</body> +</html> |
