Library for the EM-406 GPS module
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GPS.cpp
00001 /* mbed EM-406 GPS Module Library 00002 * Copyright (c) 2008-2010, sford 00003 * 00004 * Permission is hereby granted, free of charge, to any person obtaining a copy 00005 * of this software and associated documentation files (the "Software"), to deal 00006 * in the Software without restriction, including without limitation the rights 00007 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 00008 * copies of the Software, and to permit persons to whom the Software is 00009 * furnished to do so, subject to the following conditions: 00010 * 00011 * The above copyright notice and this permission notice shall be included in 00012 * all copies or substantial portions of the Software. 00013 * 00014 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 00015 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 00016 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 00017 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 00018 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 00019 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 00020 * THE SOFTWARE. 00021 */ 00022 00023 #include "GPS.h" 00024 00025 GPS::GPS(PinName tx, PinName rx) : _gps(tx, rx) { 00026 _gps.baud(9600); 00027 longitude = 0.0; 00028 latitude = 0.0; 00029 } 00030 00031 int GPS::sample() { 00032 float time; 00033 char ns, ew; 00034 int lock; 00035 00036 while(1) { 00037 getline(); 00038 00039 // Check if it is a GPGGA msg (matches both locked and non-locked msg) 00040 if(sscanf(msg, "GPGGA,%f,%f,%c,%f,%c,%d", &time, &latitude, &ns, &longitude, &ew, &lock) >= 1) { 00041 if(!lock) { 00042 longitude = 0.0; 00043 latitude = 0.0; 00044 return 0; 00045 } else { 00046 if(ns == 'S') { latitude *= -1.0; } 00047 if(ew == 'W') { longitude *= -1.0; } 00048 float degrees = trunc(latitude / 100.0f); 00049 float minutes = latitude - (degrees * 100.0f); 00050 latitude = degrees + minutes / 60.0f; 00051 degrees = trunc(longitude / 100.0f * 0.01f); 00052 minutes = longitude - (degrees * 100.0f); 00053 longitude = degrees + minutes / 60.0f; 00054 return 1; 00055 } 00056 } 00057 } 00058 } 00059 00060 float GPS::trunc(float v) { 00061 if(v < 0.0) { 00062 v*= -1.0; 00063 v = floor(v); 00064 v*=-1.0; 00065 } else { 00066 v = floor(v); 00067 } 00068 return v; 00069 } 00070 00071 void GPS::getline() { 00072 while(_gps.getc() != '$'); // wait for the start of a line 00073 for(int i=0; i<256; i++) { 00074 msg[i] = _gps.getc(); 00075 if(msg[i] == '\r') { 00076 msg[i] = 0; 00077 return; 00078 } 00079 } 00080 error("Overflowed message limit"); 00081 }
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