197 lines
8.2 KiB
C++
197 lines
8.2 KiB
C++
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/**************************************************************************/
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/*!
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@file NMEA_build.cpp
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@mainpage Adafruit Ultimate GPS Breakout
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@section intro Introduction
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This is the Adafruit GPS library - the ultimate GPS library
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for the ultimate GPS module!
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Tested and works great with the Adafruit Ultimate GPS module
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using MTK33x9 chipset
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------> http://www.adafruit.com/products/746
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Adafruit invests time and resources providing this open source code,
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please support Adafruit and open-source hardware by purchasing
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products from Adafruit!
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@section author Author
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Written by Limor Fried/Ladyada for Adafruit Industries.
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@section license License
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BSD license, check license.txt for more information
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All text above must be included in any redistribution
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*/
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/**************************************************************************/
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#include <Adafruit_GPS.h>
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#ifdef NMEA_EXTENSIONS
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/**************************************************************************/
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/*!
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@brief Build an NMEA sentence string based on the relevant variables.
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Sentences start with a $, then a two character source identifier, then
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a three character sentence name that defines the format, then a comma
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and more comma separated fields defined by the sentence name. There are
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many sentences listed that are not yet supported. Most of these sentence
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definitions were found at http://fort21.ru/download/NMEAdescription.pdf
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build() will work with other lengths for source and sentence to allow
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extension to building proprietary sentences like $PMTK220,100*2F.
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build() will not work properly in an environment that does not support
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the %f floating point formatter in sprintf(), and will return NULL.
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build() adds Carriage Return and Line Feed to sentences to conform to
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NMEA-183, so send your output with a print, not a println.
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Some of the data in these test sentences may be arbitrary, e.g. for the
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TXT sentence which has a more complicated protocol for multiple lines
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sent as a message set. Also, the data in the class variables are presumed
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to be valid, so these sentences may contain values that are stale, or
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the result of initialization rather than measurement.
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@param nmea Pointer to the NMEA string buffer. Must be big enough to
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hold the sentence. No guarantee what will be in it if the
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building of the sentence fails.
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@param thisSource Pointer to the source name string (2 upper case)
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@param thisSentence Pointer to the sentence name string (3 upper case)
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@param ref Reference for the sentence, usually relative (R) or true (T)
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@return Pointer to sentence if successful, NULL if fails
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*/
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/**************************************************************************/
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char *Adafruit_GPS::build(char *nmea, const char *thisSource,
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const char *thisSentence, char ref) {
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sprintf(nmea, "%6.2f", 123.45); // fail if sprintf() doesn't handle floats
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if (strcmp(nmea, "123.45"))
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return NULL;
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*nmea = '$';
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char *p = nmea + 1; // Pointer to move through the sentence
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strncpy(p, thisSource, strlen(thisSource));
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p += strlen(thisSource);
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strncpy(p, thisSentence, strlen(thisSentence));
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p += strlen(thisSentence);
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*p = ',';
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p += 1; // Now $XXSSS, and need to add argument fields
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// This may look inefficient, but an M0 will get down the list in about 1 us /
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// strcmp()! Put the GPS sentences from Adafruit_GPS at the top to make
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// pruning excess code easier. Otherwise, keep them alphabetical for ease of
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// reading.
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if (!strcmp(thisSentence,
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"GGA")) { //********************************************GGA
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// GGA Global Positioning System Fix Data. Time, Position and fix related
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// data for a GPS receiver
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// 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
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// | | | | | | | | | | | | | | |
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//$--GGA,hhmmss.ss,ddmm.mm,a,dddmm.mm,a,x,xx,x.x,x.x,M,x.x,M,x.x,xxxx*hh
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// 1) Time (UTC)
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// 2) Latitude
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// 3) N or S (North or South)
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// 4) Longitude
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// 5) E or W (East or West)
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// 6) GPS Quality Indicator, 0 - fix not available, 1 - GPS fix, 2 -
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// Differential GPS fix 7) Number of satellites in view, 00 - 12 8)
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// Horizontal Dilution of precision 9) Antenna Altitude above/below
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// mean-sea-level (geoid) 10) Units of antenna altitude, meters 11) Geoidal
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// separation, the difference between the WGS-84 earth
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// ellipsoid and mean-sea-level (geoid), "-" means mean-sea-level below
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// ellipsoid
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// 12) Units of geoidal separation, meters
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// 13) Age of differential GPS data, time in seconds since last SC104
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// type 1 or 9 update, null field when DGPS is not used
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// 14) Differential reference station ID, 0000-1023
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// 15) Checksum
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sprintf(p, "%09.2f,%09.4f,%c,%010.4f,%c,%d,%02d,%f,%f,M,%f,M,,",
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hour * 10000L + minute * 100L + seconds + milliseconds / 1000.,
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latitude, lat, longitude, lon, fixquality, satellites, HDOP,
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altitude, geoidheight);
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} else if (!strcmp(thisSentence,
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"GLL")) { //********************************************GLL
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// GLL Geographic Position – Latitude/Longitude
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// 1 2 3 4 5 6 7
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// | | | | | | |
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//$--GLL,llll.ll,a,yyyyy.yy,a,hhmmss.ss,A*hh
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// 1) Latitude ddmm.mm format
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// 2) N or S (North or South)
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// 3) Longitude dddmm.mm format
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// 4) E or W (East or West)
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// 5) Time (UTC)
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// 6) Status A - Data Valid, V - Data Invalid
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// 7) Checksum
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sprintf(p, "%09.4f,%c,%010.4f,%c,%09.2f,A", latitude, lat, longitude, lon,
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hour * 10000L + minute * 100L + seconds + milliseconds / 1000.);
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} else if (!strcmp(thisSentence,
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"GSA")) { //********************************************
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// GSA GPS DOP and active satellites
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// 1 2 3 14 15 16 17 18
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// | | | | | | | |
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//$--GSA,a,a,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x.x,x.x,x.x*hh
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// 1) Selection mode
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// 2) Mode
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// 3) ID of 1st satellite used for fix
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// 4) ID of 2nd satellite used for fix
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// ...
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// 14) ID of 12th satellite used for fix
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// 15) PDOP in meters
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// 16) HDOP in meters
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// 17) VDOP in meters
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// 18) Checksum
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return NULL;
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} else if (!strcmp(thisSentence,
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"RMC")) { //********************************************RMC
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// RMC Recommended Minimum Navigation Information
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// 12
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// 1 2 3 4 5 6 7 8 9 10 11 |
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// | | | | | | | | | | | |
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//$--RMC,hhmmss.ss,A,llll.ll,a,yyyyy.yy,a,x.x,x.x,xxxxxx,x.x,a*hh
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// 1) Time (UTC)
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// 2) Status, V = Navigation receiver warning
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// 3) Latitude
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// 4) N or S
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// 5) Longitude
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// 6) E or W
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// 7) Speed over ground, knots
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// 8) Track made good, degrees true
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// 9) Date, ddmmyy
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// 10) Magnetic Variation, degrees
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// 11) E or W
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// 12) Checksum
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sprintf(p, "%09.2f,A,%09.4f,%c,%010.4f,%c,%f,%f,%06d,%f,%c",
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hour * 10000L + minute * 100L + seconds + milliseconds / 1000.,
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latitude, lat, longitude, lon, speed, angle,
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day * 10000 + month * 100 + year, magvariation, mag);
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} else if (!strcmp(thisSentence,
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"TXT")) { //********************************************TXT
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// as mentioned in https://github.com/adafruit/Adafruit_GPS/issues/95
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// TXT Text Transmission
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// 1 2 3 4 5
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// | | | | |
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//$--TXT,xx,xx,xx,c--c*hh
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// 1) Total Number of Sentences 01-99
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// 2) Sentence Number 01-99
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// 3) Text Identifier 01-99
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// 4) Text String, max 61 characters
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// 5) Checksum
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sprintf(p, "01,01,23,This is the text of the sample message");
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} else {
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return NULL; // didn't find a match for the build request
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}
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addChecksum(nmea); // Successful completion
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sprintf(nmea, "%s\r\n",
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nmea); // Add Carriage Return and Line Feed to comply with NMEA-183
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return nmea; // return pointer to finished product
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}
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#endif // NMEA_EXTENSIONS
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