private void Run()
{
try
{
string workingBuffer = string.Empty;
while (true)
{
int bytesToRead = _port.BytesToRead;
if (bytesToRead > 0)
{
byte[] buffer = new byte[bytesToRead];
_port.Read(buffer, 0, buffer.Length);
string text = new string(Encoding.UTF8.GetChars(buffer));
workingBuffer += text.ToString();
int sentenceEndIndex;
while ((sentenceEndIndex = workingBuffer.IndexOf(CrLf)) != -1)
{
string sentence = workingBuffer.Substring(0, sentenceEndIndex);
if (sentence.IndexOf('$') != -1)
{
IGPSMessage message = GPSMessageParser.Parse(sentence);
if (message != null)
{
if (message is FixedDataMessage)
{
GPSPosition position = ParsePosition(message as FixedDataMessage);
if (PositionReceived != null)
{
PositionReceived(this, position);
}
}
}
}
if (sentenceEndIndex + CrLf.Length == workingBuffer.Length)
{
workingBuffer = string.Empty;
}
else
{
workingBuffer = workingBuffer.Substring(sentenceEndIndex + CrLf.Length, workingBuffer.Length - sentenceEndIndex - CrLf.Length);
}
sentenceEndIndex = workingBuffer.IndexOf(CrLf);
}
Thread.Sleep(100);
}
}
}
catch (ThreadAbortException)
{
}
}
public static IGPSMessage Parse(string sentence)
{
IGPSMessage message = null;
int checksumIndex = sentence.IndexOf("*");
if (checksumIndex == -1)
{
throw new Exception("No checksum found");
}
if (checksumIndex == sentence.Length - 1)
{
throw new Exception("No checksum after marker");
}
string checksum = sentence.Substring(checksumIndex + 1, sentence.Length - checksumIndex - 1);
sentence = sentence.Substring(0, checksumIndex);
string[] messageFields = sentence.Split(new char[] { ',' });
if (messageFields == null || messageFields.Length == 0)
{
throw new Exception("No fields in the message");
}
switch (messageFields[0])
{
case "$GPGGA":
{
FixedDataMessage fdMessage = new FixedDataMessage();
fdMessage.Timestamp = ParseTime(messageFields[1]);
fdMessage.Latitude = messageFields[2];
fdMessage.NSIndicator = ParseChar(messageFields[3]);
fdMessage.Longitude = messageFields[4];
fdMessage.EWIndicator = ParseChar(messageFields[5]);
fdMessage.PositionFix = ParsePositionFixIndicator(messageFields[6]);
fdMessage.SatallitesUsed = messageFields[7];
ParseDouble(messageFields[8], out fdMessage.HDOP, out fdMessage.IsHDOPValid);
ParseDouble(messageFields[9], out fdMessage.MSLAltitude, out fdMessage.IsMSLAltitudeValid);
fdMessage.MSLAltitudeUnits = ParseChar(messageFields[10], out fdMessage.IsMSLAltitudeUnitsValid);
ParseDouble(messageFields[11], out fdMessage.GeoidSeperation, out fdMessage.IsGeoidSeperationValid);
fdMessage.GeoidSeperationUnits = ParseChar(messageFields[12], out fdMessage.IsGeoidSeperationUnitsValid);
ParseInt(messageFields[13], out fdMessage.AgeOfDifferentialCorrection, out fdMessage.IsAgeOfDifferentialCorrectionValid);
fdMessage.DifferentialReferenceStationId = messageFields[14];
message = fdMessage;
break;
}
}
return(message);
}
