Node.js GPS NMEA parser for LS20031 and Beaglebone

ls20031_gps.js

//
//   Node.js GPS NMEA parser for LS20031 and Beaglebone
//  
//   Parses GSV/GGA strings and logs to a file.
//   GPS module outputs lat ddmm.mmmm and lon dddmm.mmmm.
//   Hardcoded for North-West hemispheres. latPole S and lonPole W are (-)
//   Author: Frank Phillips <[email protected]>
//   Uses serialport and nmea modules. Edit the require paths as necessary.

var http = require('http');
var serialport = require('/home/root/node_modules/serialport');
var nmea = require('/home/root/node_modules/nmea');
var fs = require('fs');

var port = new serialport.SerialPort('/dev/ttyO1', {
                baudrate: 115200,
                parser: serialport.parsers.readline('\r\n')});

var stream = fs.createWriteStream('/tmp/out');

stream.once('open', function(fd) {
    port.on('data',function(data){

        // Not every line of data results in a successful parse
        if (nmea.parse(data)) {
            var loc = nmea.parse(data);
        } else return;

        // Match first NMEA GSV string
        if (loc.type === 'satellite-list-partial') {
            if (loc.msgNum === 1) {
            stream.write("satsInView: " + loc.satsInView + '\n');
            }
            var ids = '';
            for (var i=0; i < loc.satellites.length; i++) {
                ids += loc.satellites[i].id + ',';
            }
            stream.write("Sats:" + ids + '\n');
        }
        // Match NMEA GGA string
        if (loc.type === 'fix') {
            stream.write(loc.latPole + loc.lat + " " + loc.lonPole + loc.lon + '\n');

            // Convert ddmm.mmmm to degrees decimal
            var deg = loc.lat.toString().slice(0,2);
            var min = loc.lat.toString().slice(2)/60;
            var d = parseFloat(deg) + parseFloat(min);

            // Convert dddmm.mmmm to degrees decimal
            var deg = loc.lon.toString().slice(0,3);
            var min = loc.lon.toString().slice(3)/60;
            var e = parseFloat(deg) + parseFloat(min);

            stream.write(d.toFixed(4) + ", -" + e.toFixed(4) + "\n");
        }
    });
});