This is a BluetoothLocationDataSource that was written for a WPF application a while back. It uses the 32feet library previously mentioned for connectivity and the dotMorten/NmeaParser (thanks Morten Nielsen) There is code specific to the framework used in the application, but I think you could extract the primary logic.
Note: Not 100% sure on my computation of Accuracy, I have done research on this topic and found differing computations of overall sigma. As a side note, accuracy is a bit of a nebulous term, what this really means is there is a certain % chance (usually 95%) that a point falls within a radius of the location given.
public class BluetoothLocationDataSource : LocationDataSource
{
private ILog4NetFacade Log { get; }
#region Private Fields
private bool _isTryingToOpen;
private MapPoint _mapPoint;
private double _velocity, _course, _accuracy;
#endregion
public BluetoothLocationDataSource(IEventAggregator eventAggregator, ILog4NetFacade log)
{
Log = log;
EventAggregator = eventAggregator;
EventAggregator.GetEvent<SendNTripCorrectionEvent>().Subscribe(OnSendNTripCorrection);
}
protected IEventAggregator EventAggregator { get; }
protected BluetoothClient BluetoothClient { get; set; }
public BluetoothDeviceInfo BluetoothDevice { get; set; }
protected override async Task OnStartAsync()
{
try
{
if ( _isTryingToOpen ) return;
if ( IsStarted ) return;
BluetoothClient = new BluetoothClient();
var devices = await BluetoothClient.DiscoverDevicesAsync(5, true, true, false);
Log.Debug($"Bluetooth found devices: {devices.Length}");
for (var i = 0; i < devices.Length; i++)
{
var device = devices[i];
Log.Debug($"Device {i}: Device Name: {device.DeviceName}");
Log.Debug($"Device {i}: Device Class: {device.ClassOfDevice.Device} {device.ClassOfDevice.Service}");
Log.Debug($"Device {i}: Service Class: {device.ClassOfDevice.Service}");
}
BluetoothDevice = devices.FirstOrDefault(d => d.ClassOfDevice.Equals(new ClassOfDevice(DeviceClass.Miscellaneous, ServiceClass.Positioning)));
if (BluetoothDevice == null)
{
Log.Debug("Bluetooth device not found");
throw new Exception("Unable to locate bluetooth device");
}
Log.Debug("Bluetooth device found");
if ( !BluetoothDevice.InstalledServices.Contains(BluetoothService.SerialPort) )
{
Log.Debug("Bluetooth device does not contain Serial Port Service");
throw new Exception("Bluetooth device is not valid for this LocationDataSource");
}
Log.Debug("Bluetooth device contains SerialPort service");
_isTryingToOpen = true;
if ( !await OpenPort() )
{
Log.Debug("Unable to Open Bluetooth port");
EventAggregator.GetEvent<GpsConnectCompleteEvent>().Publish(new GpsConnectCompleteEventArgs { ConnectSuccess = false });
return;
}
var _ = ReceiveData();
EventAggregator.GetEvent<GpsConnectCompleteEvent>().Publish(new GpsConnectCompleteEventArgs { ConnectSuccess = true });
}
catch (Exception e)
{
Log.Error(e.Message, e);
throw e;
}
}
private async Task<bool> OpenPort()
{
for (int i = 0; i < 5; i++)
{
try
{
await BluetoothClient.ConnectAsync(BluetoothDevice.DeviceAddress, BluetoothService.SerialPort);
if ( !BluetoothClient.Connected ) throw new Exception();
Log.Debug($"Bluetooth port opened after {i} attempts");
_isTryingToOpen = false;
return true;
}
catch (Exception)
{
}
}
_isTryingToOpen = false;
return false;
}
public void SendMessage()
{
var b = Encoding.ASCII.GetBytes("$JT\r\n");
BluetoothClient.Client.Send(b);
}
private async Task ReceiveData()
{
byte[] bytesReceived = new byte[256];
string result = string.Empty;
do
{
var bytes = 0;
try
{
bytes = await BluetoothClient.Client.ReceiveAsync(bytesReceived, 0, 256, SocketFlags.None);
}
catch (SocketException e)
{
Log.Error("Stopped receiving bluetooth data due to scoket exception");
Log.Error(e.Message);
_isTryingToOpen = false;
EventAggregator.GetEvent<GpsConnectCompleteEvent>().Publish(new GpsConnectCompleteEventArgs { ConnectSuccess = false });
break;
}
catch (Exception e)
{
Log.Error("Stopped receiving bluetooth data");
Log.Error(e.Message, e);
EventAggregator.GetEvent<GpsConnectCompleteEvent>().Publish(new GpsConnectCompleteEventArgs { ConnectSuccess = false });
break;
}
result = result + Encoding.ASCII.GetString(bytesReceived, 0, bytes);
if ( bytes < 10 ) continue;
string[] lines = result.Split(new[] { "\n" }, StringSplitOptions.RemoveEmptyEntries);
for (var index = 0; index < lines.Length - 1; index++)
{
var line = lines[index];
if ( line.StartsWith("$>") )
{
}
UpdateLocationFromNemaSentence(line);
}
result = lines.Last();
} while (true);
}
private void UpdateLocationFromNemaSentence(string line)
{
try
{
line = line.TrimEnd('\n', '\r');
var message = NmeaMessage.Parse(line);
ReadLocationAttributesFromMessage(message);
}
catch (Exception)
{
}
if ( _mapPoint == null || double.IsNaN(_mapPoint.X) || double.IsNaN(_mapPoint.Y) )
{
UpdateLastKnownLocation();
return;
}
UpdateLocation(new Esri.ArcGISRuntime.Location.Location(_mapPoint, _accuracy, _velocity, _course, false));
}
private void ReadLocationAttributesFromMessage(NmeaMessage message)
{
switch (message)
{
case Gpgga gpgga:
_mapPoint = new MapPoint(gpgga.Longitude, gpgga.Latitude, SpatialReference.Create(4326));
EventAggregator.GetEvent<UpdateLastGgaEvent>().Publish(gpgga.ToString());
break;
case Gpgsa gpgsa:
break;
case Gprmc gprmc:
_velocity = double.IsNaN(gprmc.Speed) ? 0 : gprmc.Speed * 0.5144;
_course = double.IsNaN(gprmc.Course) ? 0 : gprmc.Course;
_mapPoint = new MapPoint(gprmc.Longitude, gprmc.Latitude, SpatialReference.Create(4326));
break;
case Gpgsv gpgsv:
break;
case Gpgst gpgst:
double latError = gpgst.SigmaLatitudeError;
double lonError = gpgst.SigmaLongitudeError;
_accuracy = Math.Sqrt(0.5 * (Math.Pow(latError, 2) + Math.Pow(lonError, 2)));
break;
}
}
private void UpdateLastKnownLocation()
{
if ( _mapPoint == null )
{
_mapPoint = new MapPoint(double.NaN, double.NaN, SpatialReferences.Wgs84);
}
UpdateLocation(new Esri.ArcGISRuntime.Location.Location(_mapPoint, _accuracy, _velocity, _course, true));
}
protected override Task OnStopAsync()
{
BluetoothClient?.Client?.Close(250);
BluetoothClient?.Close();
BluetoothClient = null;
return Task.FromResult(true);
}
private async void OnSendNTripCorrection(SendNTripCorrectionEventArgs obj)
{
try
{
await BluetoothClient.Client.SendAsync(obj.Bytes);
}
catch (Exception e)
{
Log.Error(e.Message, e);
}
}
}
Thanks,
-Joe
