Revision 0:f3a7d716faea, committed 2014-11-01

Comitter:

jebradshaw

Date:

Sat Nov 01 13:27:11 2014 +0000

Child:

1:c266b90b4c74

Commit message:

GPSINT serial receive interrupt library for parsing GPS NMEA messages

Changed in this revision

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/GPSINT.cpp	Sat Nov 01 13:27:11 2014 +0000
@@ -0,0 +1,217 @@
+/* GPSINT.cpp
+ * Copyright (c) 2014, jbradshaw (20141101)
+ *
+ * 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 "GPSINT.h"
+
+GPSINT::GPSINT(PinName tx, PinName rx) : _gps(tx, rx) {
+    _gps.baud(4800);
+    GPSidx=0;          // Index for GPS buffer
+    GPSstate=0;        // Used to wait for '$' in GPS interrupt
+    _gps.attach(this,&GPSINT::GPSSerialRecvInterrupt, _gps.RxIrq);    // Recv interrupt handler
+}
+
+int GPSINT::nmea_validate(char *nmeastr){
+    char check[3];
+    char checkcalcstr[3];
+    int i;
+    int calculated_check;
+
+    i=0;
+    calculated_check=0;
+
+    // check to ensure that the string starts with a $
+    if(nmeastr[i] == '$')
+        i++;
+    else
+        return 0;
+
+    //No NULL reached, 75 char largest possible NMEA message, no '*' reached
+    while((nmeastr[i] != 0) && (nmeastr[i] != '*') && (i < 75)){
+        calculated_check ^= nmeastr[i];// calculate the checksum
+        i++;
+    }
+
+    if(i >= 75){
+        return 0;// the string was too long so return an error
+    }
+
+    if (nmeastr[i] == '*'){
+        check[0] = nmeastr[i+1];    //put hex chars in check string
+        check[1] = nmeastr[i+2];
+        check[2] = 0;
+    }
+    else
+        return 0;// no checksum separator found therefor invalid
+
+    sprintf(checkcalcstr,"%02X",calculated_check);
+    return((checkcalcstr[0] == check[0])
+        && (checkcalcstr[1] == check[1])) ? 1 : 0 ;
+} 
+
+void GPSINT::parseGPSString(char *GPSstrParse){
+    //check if $GPGGA string
+    if(!strncmp(GPSstrParse, "$GPGGA", 6)){
+        if (sscanf(GPSstrParse, "$GPGGA,%f,%f,%c,%f,%c,%d,%d,%f,%f,%c", &utc_time, &nmea_latitude, &ns, &nmea_longitude, &ew, &lock, &satelites, &hdop, &msl_altitude, &msl_units) >= 1) {
+//            printf("%s", GPSstrParse);
+            return;
+        }
+        else{
+ //           printf("BAD parse %s", GPSstrParse);    
+        }
+    }
+    // Check if $GPRMC string
+    else if (!strncmp(GPSstrParse, "$GPRMC", 6)){
+        if(sscanf(GPSstrParse, "$GPRMC,%f,%f,%c,%f,%c,%f,%f,%d", &utc_time, &nmea_latitude, &ns, &nmea_longitude, &ew, &speed_k, &course_d, &date) >= 1) {
+//            printf("%s", GPSstrParse);
+            return;
+        }
+        else{
+ //           printf("BAD parse %s", GPSstrParse);    
+        }
+    }
+    // GLL - Geographic Position-Lat/Lon
+    else if (!strncmp(GPSstrParse, "$GPGLL", 6)){
+        if(sscanf(GPSstrParse, "$GPGLL,%f,%c,%f,%c,%f,%c", &nmea_latitude, &ns, &nmea_longitude, &ew, &utc_time, &gll_status) >= 1) {
+//            printf("%s", GPSstrParse);
+            return;
+        }
+        else{
+ //           printf("BAD parse %s", GPSstrParse);    
+        }        
+    }
+    // VTG-Course Over Ground and Ground Speed
+    else if (!strncmp(GPSstrParse, "$GPVTG", 6)){
+        if(sscanf(GPSstrParse, "$GPVTG,%f,%c,%f,%c,%f,%c,%f,%c", &course_t, &course_t_unit, &course_m, &course_m_unit, &speed_k, &speed_k_unit, &speed_km, &speed_km_unit) >= 1) {
+//            printf("%s", GPSstrParse);
+            return;
+        }
+        else{
+//            printf("BAD parse %s", GPSstrParse);    
+        }        
+    }            
+}//parseGPSstring()
+
+void GPSINT::GPSSerialRecvInterrupt(void)
+{
+    char c;
+    c =_gps.getc();            // On receive interrupt, get the character.          
+    //    pc.printf("%c", c);
+    
+    switch(GPSstate){
+        case 0:
+            if(c =='$'){
+                GPSidx=0;
+                Temp_GPSbuf[GPSidx] = c;  //load char in current idx of array
+                GPSidx++;
+                GPSstate = 1;
+            }            
+            break;
+        case 1:                    
+            Temp_GPSbuf[GPSidx] = c;  //load char in current idx of array
+            GPSidx++;            
+            if(c == '\n'){  //if last char was a newline
+                Temp_GPSbuf[GPSidx] = '\0'; //append a NULL
+                strcpy(GPSbuf, Temp_GPSbuf);    //copy temp buf into GPS buf
+                GPSidx=0;                       //reset index
+                GPSstate = 0;                   //reset GPS state
+                if(nmea_validate(GPSbuf)){
+                    parseGPSString(GPSbuf);
+                }
+            }            
+            break;
+        
+        default:
+            break;
+            
+    }//switch state                                 
+}
+     
+float GPSINT::nmea_to_dec(float deg_coord, char nsew) {
+    int degree = (int)(deg_coord/100);
+    float minutes = deg_coord - degree*100;
+    float dec_deg = minutes / 60;
+    float decimal = degree + dec_deg;
+    if (nsew == 'S' || nsew == 'W') { // return negative
+        decimal *= -1;
+    }
+    return decimal;
+}
+
+// NAVIGATION FUNCTIONS ////////////////////////////////////////////////////////////
+float GPSINT::calc_course_to(float pointLat, float pontLong) {
+    const double d2r = PI / 180.0;
+    const double r2d = 180.0 / PI;
+    double dlat = abs(pointLat - dec_latitude) * d2r;
+    double dlong = abs(pontLong - dec_longitude) * d2r;
+    double y = sin(dlong) * cos(pointLat * d2r);
+    double x = cos(dec_latitude*d2r)*sin(pointLat*d2r) - sin(dec_latitude*d2r)*cos(pointLat*d2r)*cos(dlong);
+    return atan2(y,x)*r2d;
+}    
+ 
+/*
+var y = Math.sin(dLon) * Math.cos(lat2);
+var x = Math.cos(lat1)*Math.sin(lat2) -
+        Math.sin(lat1)*Math.cos(lat2)*Math.cos(dLon);
+var brng = Math.atan2(y, x).toDeg();
+*/
+ 
+/*
+            The Haversine formula according to Dr. Math.
+            http://mathforum.org/library/drmath/view/51879.html
+                
+            dlon = lon2 - lon1
+            dlat = lat2 - lat1
+            a = (sin(dlat/2))^2 + cos(lat1) * cos(lat2) * (sin(dlon/2))^2
+            c = 2 * atan2(sqrt(a), sqrt(1-a)) 
+            d = R * c
+                
+            Where
+                * dlon is the change in longitude
+                * dlat is the change in latitude
+                * c is the great circle distance in Radians.
+                * R is the radius of a spherical Earth.
+                * The locations of the two points in 
+                    spherical coordinates (longitude and 
+                    latitude) are lon1,lat1 and lon2, lat2.
+*/
+double GPSINT::calc_dist_to_mi(float pointLat, float pontLong) {
+    const double d2r = PI / 180.0;
+    double dlat = pointLat - dec_latitude;
+    double dlong = pontLong - dec_longitude;
+    double a = pow(sin(dlat/2.0),2.0) + cos(dec_latitude*d2r) * cos(pointLat*d2r) * pow(sin(dlong/2.0),2.0);
+    double c = 2.0 * asin(sqrt(abs(a)));
+    double d = 63.765 * c;
+    
+    return d;
+}
+ 
+double GPSINT::calc_dist_to_ft(float pointLat, float pontLong) {
+    return calc_dist_to_mi(pointLat, pontLong)*5280.0;
+}
+ 
+double GPSINT::calc_dist_to_km(float pointLat, float pontLong) {
+    return calc_dist_to_mi(pointLat, pontLong)*1.609344;
+}
+ 
+double GPSINT::calc_dist_to_m(float pointLat, float pontLong) {
+    return calc_dist_to_mi(pointLat, pontLong)*1609.344;
+}
\ No newline at end of file

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/GPSINT.h	Sat Nov 01 13:27:11 2014 +0000
@@ -0,0 +1,102 @@
+/* GPSINT.h
+ * Copyright (c) 2014, jbradshaw (20141101)
+ *
+ * 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.
+ */
+ 
+/* This GPSINT library class retrieves, parses, and updates variables using
+  a serial receive interrupt.  The library was written using the Trimble
+  Copernicus II moduls bus should work on any NMEA 4800 baud output device.
+  The relatively slow 4800 baud allows for plenty of processing time during
+  byte receptions in the interrupt.  Using the mbed LPC 100MHz unit, it takes
+  about 340us to process, and parse the 2 default GPGGA and GPZTG strings.*/
+
+#include "mbed.h"
+
+#ifndef GPSINT_H
+#define GPSINT_H
+
+#define PI (3.14159265359)
+#define GPSBUFSIZE  256       // GPS buffer size
+
+/**
+ * GPSINT Class.
+ */
+ 
+class GPSINT{
+public:
+    /**
+     * Constructor.
+     * @param gps - Serial port pins attached to the gps
+     */ 
+    GPSINT(PinName tx, PinName rx);
+    int nmea_validate(char *nmeastr);
+    void parseGPSString(char *GPSstrParse);
+    void GPSSerialRecvInterrupt(void);
+    float nmea_to_dec(float deg_coord, char nsew);
+    float calc_course_to(float pointLat, float pontLong);
+    double calc_dist_to_mi(float pointLat, float pontLong);
+    double calc_dist_to_ft(float pointLat, float pontLong);
+    double calc_dist_to_km(float pointLat, float pontLong);
+    double calc_dist_to_m(float pointLat, float pontLong);
+        
+    // GPSINT variables
+    char GPSbuf[GPSBUFSIZE];     // Receive buffer. 
+    char Temp_GPSbuf[GPSBUFSIZE];// Receive buffer. 
+    char GPSidx;               // Read by background, written by Int Handler.
+    int GPSstate;              //set when successful GPS string is received
+    
+    // calculated values
+    float dec_longitude;
+    float dec_latitude;
+    float altitude_ft;
+    
+    // GGA - Global Positioning System Fixed Data
+    float nmea_longitude;
+    float nmea_latitude;    
+    float utc_time;
+    char ns, ew;
+    int lock;
+    int satelites;
+    float hdop;
+    float msl_altitude;
+    char msl_units;
+    
+    // RMC - Recommended Minimmum Specific GNS Data
+    char rmc_status;
+    float speed_k;
+    float course_d;
+    int date;
+    
+    // GLL
+    char gll_status;
+    
+    // VTG - Course over ground, ground speed
+    float course_t; // ground speed true
+    char course_t_unit;
+    float course_m; // magnetic
+    char course_m_unit;
+    char speed_k_unit;
+    float speed_km; // speek km/hr
+    char speed_km_unit;
+private:
+    Serial _gps;
+};
+
+#endif /* GPSINT_H */
\ No newline at end of file