Darren Ulrich / GPSISR

A GPS serial interrupt service routine that has an on the fly nmea parser. Works with a STM32F411RE and a Adafruit GPS logger.

Dependents:   Bicycl_Computer_NUCLEO-F411RE Bicycl_Computer_NUCLEO-L476RG

Fork of GPS by Simon Ford

main.cpp

#include "mbed.h"
#include "GPSISR.h"

#define PIN_RX_GPS      PA_12 //GPS Shield RX pin
#define PIN_TX_GPS      PA_11 //GPS Shield TX pin
Serial pc(USBTX, USBRX);

// Set up serial interrupe service handler for gps characters.
GPS MyGPS(PIN_TX_GPS,PIN_RX_GPS, 9600);
int main()
{
    while (1) {
	if (MyGPS.dataready()) {
					MyGPS.read();
					pc.printf("NMEA has valid data");
					pc.printf("Sats : %d \n", MyGPS.buffer.satellites);
					pc.printf("%d-%d-%d\n", MyGPS.buffer.month, MyGPS.buffer.day, MyGPS.buffer.year);
					pc.printf("%d:%d:%d\n", MyGPS.buffer.hours, MyGPS.buffer.minutes, MyGPS.buffer.seconds);
	}
	else {
                pc.printf("NMEA has no valid data");
	}   
   }  
}

nav.cpp

Committer:
trevieze
Date:
2017-03-01
Revision:
5:c5f700c1e1af

File content as of revision 5:c5f700c1e1af:

    /*
    File:       nav.cpp
    Version:    0.1.0
    Date:       Feb. 28, 2017
    License:    GPL v2
    
    Navigation class
    
    ****************************************************************************
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    ****************************************************************************
 */
       #include <math.h>
       #include "nav.h" 
       // Calculate the heading
        double NAV::CalculateDistance (double from_lat, double from_lon, double to_lat, double to_lon)
        {
            double R = 6371e3;
            double lat1 = DegreeToRadian(from_lat);
            double lat2 = DegreeToRadian(to_lat);
            double deltaLat = DegreeToRadian(to_lat - from_lat);
            double deltaLong = DegreeToRadian(to_lon - from_lon);

            double a = sin(deltaLat / 2) * sin(deltaLat / 2) + cos(lat1) * cos(lat2) * sin(deltaLong / 2) * sin(deltaLong / 2);
            double c = 2 * atan2(sqrt(a), sqrt(1 - a));
            double d = R * c;

            return d;
        }
        
        // Calculate bearing
        double NAV::CalculateBearing(double from_lat, double from_lon, double to_lat, double to_lon)
        {
            double lat1 = DegreeToRadian(from_lat);
            double lat2 = DegreeToRadian(to_lat);
            double long1 = DegreeToRadian(from_lon);
            double long2 = DegreeToRadian(to_lon);

            double y = sin(long2 - long1) * cos(lat2);
            double x = cos(lat1) * sin(lat2) - sin(lat1) * cos(lat2) * cos(long2 - long1);

            double bearing = RadianToDegree(atan2(y, x));

            // Correct "wrap around" if necessary
            if (bearing < 0) bearing = 360.0 + bearing;
            if (bearing > 360.0) bearing = bearing - 360.0;

            return bearing;
        }
        
        /*
        This function takes as input the next gps coordinate that the boat is suppossed to achieve and calculates the compass
        heading to the waypoint
        Jeff Witten - 05/26/14 from Github VT-SailBOT/Navigation sailbot.c
        */
        int NAV::direction_to_next_point (double from_lat, double from_lon, double to_lat, double to_lon)
        {
            double dist_lat = 111132.954 - 559.822*cos(2*from_lat) + 1.1175*cos(4*from_lat);
            double dist_lon = PI/180*6367449*cos(from_lat);
            double lat_meter = fabs(fabs(to_lat) - fabs(from_lat))*dist_lat;
            double lon_meter = fabs(fabs(to_lon) - fabs(from_lon))*dist_lon;
            double difference = (lat_meter/lon_meter);
            double  degree = atan(difference);  
            degree = fabs(degree*180/PI);
            int angle = 0;
    
            if(to_lat >= from_lat && to_lon >= from_lon)           //Quadrant I
                angle = 90 - degree;
            else if(to_lat <= from_lat && to_lon >= from_lon)          //Quadrant II
                angle = 90 + degree;
            else if(to_lat <= from_lat && to_lon <= from_lon)          //Quadrant III
                angle = 270 - degree;
            else if(to_lat >= from_lat && to_lon <= from_lon)          //Quadrant IV
                angle = 270 + degree;

        return angle;
        }
        
        /*
        This function takes as input the gps coordinates of the boat and the gps coordinates of a waypoint that the boat desires to approach
        The function then sets a flag based on whether or not the boat is within a predetermined perimeter of the waypoint
        Approach:
        1.) Latitude and Longitude of San Francisco = 37.7844 N, 122.4167 W
        2.) At 40 degrees North: 1 degree latitude = 111.03 km, 1 degree longitude = 85.39 km
        3.) 111.03 = 85.39 * (1.30027) - used to correct approximately rectangular lat/lon grid to approximately square
        4.) Through unit analysis, 1 meter = 0.0000111509 degrees longitude 
        Jeff Witten - 03/27/14 from Github VT-SailBOT/Navigation sailbot.c
        */
        int NAV::point_proximity(double from_lat, double from_lon, double to_lat, double to_lon)
        {
        int number = 0;
        double dist_lat = 111132.954 - 559.822*cos(2*from_lat) + 1.1175*cos(4*from_lat);
        double dist_lon = PI/180*6367449*cos(from_lat);
        double lat_meter = fabs(fabs(to_lat) - fabs(from_lat))*dist_lat;
        double lon_meter = fabs(fabs(to_lon) - fabs(from_lon))*dist_lon;
        distance = sqrt(pow(lat_meter, 2) + pow(lon_meter,2));

        if (distance <= point_proximity_radius){
            number = 1;
        } else {
            number = 0;
        }    
            return number;
        }
        
        /**
 * \brief Calculate distance between two points
 * This function uses an algorithm for an oblate spheroid earth model.
 * The algorithm is described here: 
 * http://www.ngs.noaa.gov/PUBS_LIB/inverse.pdf
 * \return Distance in meters
 */
double NAV::distance_ellipsoid(double from_lat,  double from_lon, double from_azimuth, double to_lat, double to_lon, double to_azimuth)
{
    /* All variables */
    double f, a, b, sqr_a, sqr_b;
    double L, phi1, phi2, U1, U2, sin_U1, sin_U2, cos_U1, cos_U2;
    double sigma, sin_sigma, cos_sigma, cos_2_sigmam, sqr_cos_2_sigmam, sqr_cos_alpha, lambda, sin_lambda, cos_lambda, delta_lambda;
    int remaining_steps; 
    double sqr_u, A, B, delta_sigma;
 
    if ((from_lat == to_lat) && (from_lon == to_lon))
    { /* Identical points */
        if ( from_azimuth != 0 )
            from_azimuth = 0;
        if ( to_azimuth != 0 )
            to_azimuth = 0;
        return 0;    
    } /* Identical points */

    /* Earth geometry */
    f = NMEA_EARTH_FLATTENING;
    a = NMEA_EARTH_SEMIMAJORAXIS_M;
    b = (1 - f) * a;
    sqr_a = a * a;
    sqr_b = b * b;

    /* Calculation */
    L = to_lon - from_lon;
    phi1 = from_lat;
    phi2 = to_lat;
    U1 = atan((1 - f) * tan(phi1));
    U2 = atan((1 - f) * tan(phi2));
    sin_U1 = sin(U1);
    sin_U2 = sin(U2);
    cos_U1 = cos(U1);
    cos_U2 = cos(U2);

    /* Initialize iteration */
    sigma = 0;
    sin_sigma = sin(sigma);
    cos_sigma = cos(sigma);
    cos_2_sigmam = 0;
    sqr_cos_2_sigmam = cos_2_sigmam * cos_2_sigmam;
    sqr_cos_alpha = 0;
    lambda = L;
    sin_lambda = sin(lambda);                            
    cos_lambda = cos(lambda);                       
    delta_lambda = lambda;
    remaining_steps = 20; 

    while ((delta_lambda > 1e-12) && (remaining_steps > 0)) 
    { /* Iterate */
        /* Variables */
        double tmp1, tmp2, tan_sigma, sin_alpha, cos_alpha, C, lambda_prev; 

        /* Calculation */
        tmp1 = cos_U2 * sin_lambda;
        tmp2 = cos_U1 * sin_U2 - sin_U1 * cos_U2 * cos_lambda;  
        sin_sigma = sqrt(tmp1 * tmp1 + tmp2 * tmp2);                
        cos_sigma = sin_U1 * sin_U2 + cos_U1 * cos_U2 * cos_lambda;   
        tan_sigma = sin_sigma / cos_sigma;                  
        sin_alpha = cos_U1 * cos_U2 * sin_lambda / sin_sigma;  
        cos_alpha = cos(asin(sin_alpha));                 
        sqr_cos_alpha = cos_alpha * cos_alpha;                     
        cos_2_sigmam = cos_sigma - 2 * sin_U1 * sin_U2 / sqr_cos_alpha;
        sqr_cos_2_sigmam = cos_2_sigmam * cos_2_sigmam; 
        C = f / 16 * sqr_cos_alpha * (4 + f * (4 - 3 * sqr_cos_alpha));
        lambda_prev = lambda; 
        sigma = asin(sin_sigma); 
        lambda = L + 
            (1 - C) * f * sin_alpha
            * (sigma + C * sin_sigma * (cos_2_sigmam + C * cos_sigma * (-1 + 2 * sqr_cos_2_sigmam)));                                                
        delta_lambda = lambda_prev - lambda; 
        if ( delta_lambda < 0 ) delta_lambda = -delta_lambda; 
        sin_lambda = sin(lambda);
        cos_lambda = cos(lambda);
        remaining_steps--; 
    }  /* Iterate */

    /* More calculation  */
    sqr_u = sqr_cos_alpha * (sqr_a - sqr_b) / sqr_b; 
    A = 1 + sqr_u / 16384 * (4096 + sqr_u * (-768 + sqr_u * (320 - 175 * sqr_u)));
    B = sqr_u / 1024 * (256 + sqr_u * (-128 + sqr_u * (74 - 47 * sqr_u)));
    delta_sigma = B * sin_sigma * ( 
        cos_2_sigmam + B / 4 * ( 
        cos_sigma * (-1 + 2 * sqr_cos_2_sigmam) -
        B / 6 * cos_2_sigmam * (-3 + 4 * sin_sigma * sin_sigma) * (-3 + 4 * sqr_cos_2_sigmam)
        ));

    /* Calculate result */
    if ( from_azimuth != 0 )
    {
        double tan_alpha_1 = cos_U2 * sin_lambda / (cos_U1 * sin_U2 - sin_U1 * cos_U2 * cos_lambda);
        from_azimuth = atan(tan_alpha_1);
    }
    if ( to_azimuth != 0 )
    {
        double tan_alpha_2 = cos_U1 * sin_lambda / (-sin_U1 * cos_U2 + cos_U1 * sin_U2 * cos_lambda);
        to_azimuth = atan(tan_alpha_2);
    }

    return b * A * (sigma - delta_sigma);
}
        
        
        // Convert Degrees to Radians
        double NAV::DegreeToRadian(double angle)
        {
            return PI * angle / 180.0;
        }
        
       // Convert Radians to Degrees
        double NAV::RadianToDegree(double angle)
        {
            return angle * (180.0 / PI);
        }