Try my gps string parser http://www.gpsxml.com/gpsxml/service.asmx?op=GPS2XML

I need somebody to test my mobile APP. You can download the cab file from http://gps.gpsxml.com/viewtopic.php?t=4

Please feel free to give any comments, suggestions or ideas

Thanks
Imtiyaz Momin
http://gps.gpsxml.com/
imtu80@hotmail.com

The NMEA protocol specifies that the last parameter is immediately followed by "*" and a 2-cfharacter checksum.  For example, 3.45,"W"*1A is valid as is 200804,,*1A.  In the fist case there is data in the last parameter and in the second case, because the last parameter has been omitted. we effectively have "200804,," & "" & "*" & "1A".  That is the data string upto the second last parameter and it's following comma, the omitted final parameter, the asterisc to denote both end of data and the start of  the checksum, and finally the 2-character checksum.

Jon's excellent articles give us the start for writing our code but does say that additional error trapping is required.

My change to the GetWords function is:

    Public Function GetWords(ByVal sentence As String) As String()

        Dim temp As String

        temp = sentence.Substring(0, sentence.IndexOf("*")) & ",*"

        Return temp.Split(","c)

    End Function

 

The checksum routine has been modified slightly to clarify the Select statement.

The "$" case is used to initialise Checksum and the If statement in the Else case has been removed.  This works because Checksum = value gives the same result as Checksum = 0 Xor value when processing the first byte.

 

    ' Calculates the checksum for a sentence

    Public Function GetChecksum(ByVal sentence As String) As String

        ' Loop through all chars to get a checksum

        Dim Character As Char

        Dim Checksum As Integer = 0

        For Each Character In sentence

            Select Case Character

                Case "$"c

                    ' Ignore the dollar sign

                    Checksum = 0

                Case "*"c

                    ' Stop processing before the asterisk

                    Exit For

                Case Else

                    ' XOR the checksum with this character's value

                    Checksum = Checksum Xor Convert.ToByte(Character)

            End Select

        Next

        ' Return the checksum formatted as a two-character hexadecimal

        Return Checksum.ToString("X2")

    End Function

Hi , 

I need the same program as well.Can you find any information.Please contact me.

tunc@te-mob.com