GpsClient.cs

using System;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Windows.Devices.Enumeration;
using Windows.Devices.Geolocation;
using Windows.Devices.SerialCommunication;

namespace Mikaboshi.Iot.LocationPost
{
    public class GpsClient
    {
        DeviceInformation device;
        SerialDevice serialPort;

        Stream readStream;

        public BasicGeoposition Position { get; private set; }
        public DateTimeOffset PositionSourceTime { get; private set; }
        public double Heading { get; private set; }
        public bool Succeeded { get; private set; }
        public int Count { get; private set; }

        public event EventHandler LoggingStarted;
        public event EventHandler<GpsPositionEventArgs> PositionChanged;

        public async Task InitializeAsync()
        {
            // シリアルポートの初期化
            var selector = SerialDevice.GetDeviceSelector();
            var devices = await DeviceInformation.FindAllAsync(selector);

            this.device = devices.FirstOrDefault();
        }

        public async Task OpenPort()
        {
            if (this.device == null) return;

            this.serialPort = await SerialDevice.FromIdAsync(this.device.Id);
            this.serialPort.BaudRate = 9600;

            this.readStream = this.serialPort.InputStream.AsStreamForRead(0);
        }

        public async void Listen()
        {
            try
            {
                if (this.serialPort == null) return;

                while (true)
                {
                    await ReadAsync();
                }
            }
            catch (Exception ex)
            {

            }
            finally
            {
                if (this.readStream != null)
                {
                    this.readStream.Dispose();
                    this.readStream = null;
                }
            }
        }

        private async Task ReadAsync()
        {
            var buf = new StringBuilder();
            var readStart = false;
            var carriageReturn = false;
            while (true)
            {
                var c = (char)this.readStream.ReadByte();
                if (c < 0) break;

                if (c == '$')
                {
                    if (readStart)
                    {
                        // リード中に $ がきたら異常と見なしてリセットする
                        buf.Clear();
                        readStart = false;
                        continue;
                    }

                    readStart = true;
                }

                if (!readStart)
                {
                    continue;
                }

                buf.Append(c);

                if (c == '\r')
                {
                    carriageReturn = true;
                }
                else if (c == '\n' && carriageReturn)
                {
                    break;
                }
                else
                {
                    carriageReturn = false;
                }
            }

            var str = buf.ToString();
            Debug.WriteLine(str);
            await ParseAsync(str);
        }

        private async Task ParseAsync(string message)
        {
            using (var sr = new StringReader(message))
            {
                while (sr.Peek() > -1)
                {
                    var d = await sr.ReadLineAsync();
                    var s = d.Split(',');
                    if (s.Length < 0) return;

                    switch (s[0])
                    {
                        case "$GPRMC":
                            Gprmc(s);
                            break;
                        default:
                            break;
                    }
                }
            }
        }


        /// <summary>
        /// 緯度・経度・進行方位・速度のデータ
        /// </summary>
        /// <param name="data"></param>
        private void Gprmc(string[] data)
        {
            if (data.Length < 12) return;

            // R は Raw

            // UTC 時刻。 hhmmss.fff
            var timeR = data[1];
            // ステータス。 V = 警告 / A = 有効
            var statusR = data[2];
            // 緯度。 dddmm.mmmm
            var latitudeR = data[3];
            // N = 北緯 / S = 南緯
            var latitudePollR = data[4];
            // 経度。 dddmm.mmmm
            var longitudeR = data[5];
            // E = 東経 / W = 西経
            var longitudePollR = data[6];
            // 移動速度。 knot
            var speedR = data[7];
            // 移動方位。
            var directionR = data[8];
            // UTC 日付。 ddmmyy
            var dateR = data[9];
            // 磁北と真北の差。
            var mDirectR = data[10];
            // 磁北と真北の差の方向。 E = 東
            var mDirectPollR = data[11];
            // モード。
            var modeR = data[12];

            // 時間
            var date = ParseDateTime(dateR, timeR).ToLocalTime();

            if (statusR != "A")
            {
                this.Succeeded = false;
                return;
            }

            // 緯度
            var latitude1 = double.Parse(latitudeR) / 100;
            var latitude2 = (int)Math.Floor(latitude1);
            var latitude3 = (latitude1 % 1.0) * 100;
            var latitude = latitude2 + latitude3 / 60;
            if (latitudePollR == "S") latitude *= -1;

            // 経度
            var longitude1 = double.Parse(longitudeR) / 100;
            var longitude2 = (int)Math.Floor(longitude1);
            var longitude3 = (longitude1 % 1.0) * 100;
            var longitude = longitude2 + longitude3 / 60;
            if (longitudePollR == "W") longitude *= -1;

            // 移動速度
            const double knotToKph = 1.852;
            var kph = double.Parse(speedR) * knotToKph;

            this.Succeeded = true;
            this.Position = new BasicGeoposition { Latitude = latitude, Longitude = longitude };
            this.PositionSourceTime = date;
            this.Count++;

            if (this.Count == 1)
            {
                this.LoggingStarted?.Invoke(this, EventArgs.Empty);
            }

            var heading = 0d;
            double.TryParse(directionR, out heading);
            this.Heading = heading;

            this.PositionChanged?.Invoke(this, new GpsPositionEventArgs(this.Position, this.PositionSourceTime, this.Heading, this.Succeeded, this.Count));
        }

        /// <summary>
        /// 日付と時刻を <see cref="DateTimeOffset"/> として変換します。時刻は <see cref="DateTimeOffset.UtcNow"/> で示されるタイムゾーンで返します。
        /// </summary>
        /// <param name="date"></param>
        /// <param name="time"></param>
        /// <returns></returns>
        private static DateTimeOffset ParseDateTime(string date, string time)
        {
            var year = int.Parse("20" + date.Substring(4, 2));
            var month = int.Parse(date.Substring(2, 2));
            var day = int.Parse(date.Substring(0, 2));
            var hour = int.Parse(time.Substring(0, 2));
            var minute = int.Parse(time.Substring(2, 2));
            var second = int.Parse(time.Substring(4, 2));
            var mSecond = double.Parse("0" + time.Substring(6));
            var result = new DateTimeOffset(year, month, day, hour, minute, second, (int)(mSecond * 1000), DateTimeOffset.UtcNow.Offset);
            result = result.ToLocalTime();

            return result;
        }
    }
}

GpsPositionEventArgs.cs

using System;
using Windows.Devices.Geolocation;

namespace Mikaboshi.Iot.LocationPost
{
    public class GpsPositionEventArgs : EventArgs
    {
        public BasicGeoposition Position { get; }
        public DateTimeOffset PositionSourceTime { get; }
        public double Heading { get; }
        public bool Succeeded { get; }
        public int Count { get; }

        public GpsPositionEventArgs(BasicGeoposition position, DateTimeOffset sourceTime, double heading, bool succeeded, int count)
        {
            this.Position = position;
            this.PositionSourceTime = sourceTime;
            this.Heading = heading;
            this.Succeeded = succeeded;
            this.Count = count;
        }
    }
}