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The Core of An NMEA Interpreter

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The Core of An NMEA Interpreter

The first step in making an NMEA interpreter is writing a method which does two things: separating each sentence into its individual words and examining the first word to figure out what information is available to extract. Listing 1-1 shows the start of the interpreter class. (Listing 1-1: The core of an NMEA interpreter is a function which divides NMEA sentences into individual words.)

'*******************************************************
'**  A basic NMEA interpreter
'*******************************************************
Public Class NmeaInterpreter
  ' Processes information from the GPS receiver
  Public Function Parse(ByVal sentence As String) As Boolean
    ' Divide the sentence into words
    Dim Words() As String = GetWords(sentence)
    ' Look at the first word to decide where to go next
    Select Case Words(0)
      Case "$GPRMC"      ' A "Recommended Minimum" sentence was found!
        ' Indicate that the sentence was recognized
        Return True
      Case Else
        ' Indicate that the sentence was not recognized
        Return False
    End Select
  End Function
  ' Divides a sentence into individual words
  Public Function GetWords(ByVal sentence As String) As String()
    Return sentence.Split(","c)
  End Function
End Class

Written By Jon Person (http://www.gpsdotnet.com)

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