Diff: GPS.cpp

Revision:

0:15611c7938a3

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/GPS.cpp	Tue Jun 08 14:10:27 2010 +0000
@@ -0,0 +1,81 @@
+/* mbed EM-406 GPS Module Library
+ * Copyright (c) 2008-2010, sford
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+ 
+#include "GPS.h"
+
+GPS::GPS(PinName tx, PinName rx) : _gps(tx, rx) {
+    _gps.baud(4800);    
+    longitude = 0.0;
+    latitude = 0.0;        
+}
+
+int GPS::sample() {
+    float time;
+    char ns, ew;
+    int lock;
+
+    while(1) {        
+        getline();
+
+        // Check if it is a GPGGA msg (matches both locked and non-locked msg)
+        if(sscanf(msg, "GPGGA,%f,%f,%c,%f,%c,%d", &time, &latitude, &ns, &longitude, &ew, &lock) >= 1) { 
+            if(!lock) {
+                longitude = 0.0;
+                latitude = 0.0;        
+                return 0;
+            } else {
+                if(ns == 'S') {    latitude  *= -1.0; }
+                if(ew == 'W') {    longitude *= -1.0; }
+                float degrees = trunc(latitude / 100.0f);
+                float minutes = latitude - (degrees * 100.0f);
+                latitude = degrees + minutes / 60.0f;    
+                degrees = trunc(longitude / 100.0f * 0.01f);
+                minutes = longitude - (degrees * 100.0f);
+                longitude = degrees + minutes / 60.0f;
+                return 1;
+            }
+        }
+    }
+}
+
+float GPS::trunc(float v) {
+    if(v < 0.0) {
+        v*= -1.0;
+        v = floor(v);
+        v*=-1.0;
+    } else {
+        v = floor(v);
+    }
+    return v;
+}
+
+void GPS::getline() {
+    while(_gps.getc() != '$');    // wait for the start of a line
+    for(int i=0; i<256; i++) {
+        msg[i] = _gps.getc();
+        if(msg[i] == '\r') {
+            msg[i] = 0;
+            return;
+        }
+    }
+    error("Overflowed message limit");
+}