Andrew Lindsay / GPS

Basic GPS message parser

Fork of GPS by Simon Ford

GPS.cpp@3:ac28455d8e5a, 2017-08-22 (annotated)

Committer:
SomeRandomBloke
Date:
Tue Aug 22 15:23:05 2017 +0000
Revision:
3:ac28455d8e5a
Parent:
2:8c97b7918a94 
Added Altitude

Who changed what in which revision?

UserRevisionLine numberNew contents of line
simon 0:15611c7938a3 1 /* mbed EM-406 GPS Module Library
simon 0:15611c7938a3 2 * Copyright (c) 2008-2010, sford
simon 0:15611c7938a3 3 *
simon 0:15611c7938a3 4 * Permission is hereby granted, free of charge, to any person obtaining a copy
simon 0:15611c7938a3 5 * of this software and associated documentation files (the "Software"), to deal
simon 0:15611c7938a3 6 * in the Software without restriction, including without limitation the rights
simon 0:15611c7938a3 7 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
simon 0:15611c7938a3 8 * copies of the Software, and to permit persons to whom the Software is
simon 0:15611c7938a3 9 * furnished to do so, subject to the following conditions:
simon 0:15611c7938a3 10 *
simon 0:15611c7938a3 11 * The above copyright notice and this permission notice shall be included in
simon 0:15611c7938a3 12 * all copies or substantial portions of the Software.
simon 0:15611c7938a3 13 *
simon 0:15611c7938a3 14 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
simon 0:15611c7938a3 15 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
simon 0:15611c7938a3 16 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
simon 0:15611c7938a3 17 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
simon 0:15611c7938a3 18 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
simon 0:15611c7938a3 19 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
simon 0:15611c7938a3 20 * THE SOFTWARE.
simon 0:15611c7938a3 21 */
simon 0:15611c7938a3 22
simon 0:15611c7938a3 23 #include "GPS.h"
simon 0:15611c7938a3 24
SomeRandomBloke 2:8c97b7918a94 25 GPS::GPS(PinName tx, PinName rx, int baudrate) : _gps(tx, rx) {
SomeRandomBloke 2:8c97b7918a94 26 _gps.baud(baudrate);
simon 0:15611c7938a3 27 longitude = 0.0;
SomeRandomBloke 3:ac28455d8e5a 28 latitude = 0.0;
SomeRandomBloke 3:ac28455d8e5a 29 altitude = 0.0;
simon 0:15611c7938a3 30 }
simon 0:15611c7938a3 31
simon 0:15611c7938a3 32 int GPS::sample() {
SomeRandomBloke 1:1f849dbf3b8b 33 //float time;
simon 0:15611c7938a3 34 char ns, ew;
simon 0:15611c7938a3 35 int lock;
SomeRandomBloke 3:ac28455d8e5a 36 int satsInUse;
SomeRandomBloke 3:ac28455d8e5a 37 float hdop;
simon 0:15611c7938a3 38
simon 0:15611c7938a3 39 while(1) {
simon 0:15611c7938a3 40 getline();
simon 0:15611c7938a3 41
simon 0:15611c7938a3 42 // Check if it is a GPGGA msg (matches both locked and non-locked msg)
SomeRandomBloke 1:1f849dbf3b8b 43 // GPGGA,212700.000,5124.4324,N,00115.7464,W,1,8,1.30,113.7,M,47.5,M,,*47
SomeRandomBloke 1:1f849dbf3b8b 44 // Position -1.929107, 51.407211
SomeRandomBloke 1:1f849dbf3b8b 45 // 51.4136298,-1.2670097
SomeRandomBloke 1:1f849dbf3b8b 46 //Position -1.262323, 51.407383
SomeRandomBloke 3:ac28455d8e5a 47 if(sscanf(msg, "GPGGA,%f,%f,%c,%f,%c,%d,%d,%f,%f", &time, &latitude, &ns, &longitude, &ew, &lock, &satsInUse, &hdop, &altitude) >= 1) {
simon 0:15611c7938a3 48 if(!lock) {
simon 0:15611c7938a3 49 longitude = 0.0;
SomeRandomBloke 3:ac28455d8e5a 50 latitude = 0.0;
SomeRandomBloke 3:ac28455d8e5a 51 altitude = 0;
simon 0:15611c7938a3 52 return 0;
simon 0:15611c7938a3 53 } else {
SomeRandomBloke 1:1f849dbf3b8b 54 //printf("%s\n\r",msg);
simon 0:15611c7938a3 55 if(ns == 'S') { latitude *= -1.0; }
simon 0:15611c7938a3 56 if(ew == 'W') { longitude *= -1.0; }
simon 0:15611c7938a3 57 float degrees = trunc(latitude / 100.0f);
simon 0:15611c7938a3 58 float minutes = latitude - (degrees * 100.0f);
SomeRandomBloke 1:1f849dbf3b8b 59 //printf("LAT degrees %f, minutes %f\n\r",degrees,minutes);
SomeRandomBloke 1:1f849dbf3b8b 60 latitude = degrees + (minutes / 60.0f);
SomeRandomBloke 1:1f849dbf3b8b 61
SomeRandomBloke 1:1f849dbf3b8b 62 degrees = trunc(longitude / 100.0f); // * 0.01f);
simon 0:15611c7938a3 63 minutes = longitude - (degrees * 100.0f);
SomeRandomBloke 1:1f849dbf3b8b 64 //printf("LON degrees %f, minutes %f\n\r",degrees,minutes);
SomeRandomBloke 1:1f849dbf3b8b 65 longitude = degrees + (minutes / 60.0f);
simon 0:15611c7938a3 66 return 1;
simon 0:15611c7938a3 67 }
simon 0:15611c7938a3 68 }
simon 0:15611c7938a3 69 }
simon 0:15611c7938a3 70 }
simon 0:15611c7938a3 71
simon 0:15611c7938a3 72 float GPS::trunc(float v) {
SomeRandomBloke 2:8c97b7918a94 73 if(v < 0.0f) {
SomeRandomBloke 2:8c97b7918a94 74 v*= -1.0f;
simon 0:15611c7938a3 75 v = floor(v);
SomeRandomBloke 2:8c97b7918a94 76 v*=-1.0f;
simon 0:15611c7938a3 77 } else {
simon 0:15611c7938a3 78 v = floor(v);
simon 0:15611c7938a3 79 }
simon 0:15611c7938a3 80 return v;
simon 0:15611c7938a3 81 }
simon 0:15611c7938a3 82
simon 0:15611c7938a3 83 void GPS::getline() {
simon 0:15611c7938a3 84 while(_gps.getc() != '$'); // wait for the start of a line
SomeRandomBloke 2:8c97b7918a94 85 for(int i=0; i<255; i++) {
simon 0:15611c7938a3 86 msg[i] = _gps.getc();
SomeRandomBloke 2:8c97b7918a94 87 // printf("%c",msg[i]);
simon 0:15611c7938a3 88 if(msg[i] == '\r') {
simon 0:15611c7938a3 89 msg[i] = 0;
simon 0:15611c7938a3 90 return;
simon 0:15611c7938a3 91 }
simon 0:15611c7938a3 92 }
SomeRandomBloke 2:8c97b7918a94 93 // error("Overflowed message limit");
SomeRandomBloke 1:1f849dbf3b8b 94 // printf("Overflow");
simon 0:15611c7938a3 95 }