Diff: GPS.cpp

Revision:

0:0f423a982334

Child:

1:71e46131743f

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/GPS.cpp	Fri Jul 27 15:07:00 2012 +0000
@@ -0,0 +1,65 @@
+/* GPS class for mbed Microcontroller
+ * Copyright (c) 2008, sford
+ */
+
+#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");
+}
+