TCS-GPS LOG RECORD DESCRIPTION effective on April 15th 2004
Example: $DPTG2,2004/02/08,12:34:45,MAXGPS,360,347,4410.9482,N,01158.9260,E,184,
4,5,1,S,1,,69,,,,12,35,1,E,10.9,*13

A complete LOG download example is available on line.

Details:

Field Example Comment
Sentence ID $DPTG2 Sentence identifier
Date 2003/01/15 date in format yyyy/mm/dd
Time 20:35:02 Time in format hh:mm:ss
TCS ID TCS-GPS-01 TCS board identifier (user programmable) 10 characters
smsc 517 Counter of SMS that have been sent (4 digits)
si 30 Sampling interval in seconds
Latitude 4413.5589 Latitude in degrees, minutes and 1/10000 of a minute ( i.e. 44º 13.5589 ' )
N/S Indicator N North South emisphere indicator
Longitude 048.0984 Longitude in degrees, minutes and 1/10000 of a minute ( i.e. 0º 48.0984' )
E/W Indicator E East west of Greenwich indicator
Altitude 33.0 Altitude over sea level in meters
Ground speed 0.00 Speed over ground in Km/h
Satellites used 8 Number of satellites received and used to compute position (maximum 12)
Input 1 0 Logic status of input 1 (TTL)
Mark M
  • L = logged in standard mode
  • S = logged in smart mode
  • A = logged upon acceleration
  • M = logged upon input 1
  • G = logged upon GLG
  • P = logged and sent by SMS (or GPRS)
    • Output 1 0 Logic status of Output 1
    void   void,future use
    Heading 93 Heading degrees
    void   void for future use
    void   void for future use
    void   void for future use
    Accel. Axis X 12 X max acceleration value range 0-255
    Accel. Axis Y 35 Y max acceleration value range 0-255
    Analog input 1 Analog input value (from 8 bit ADC) range 0-255
    powtype E Power supply type: E=external, B=backup batteries
    battlev 12.2 Backup battery voltage level
    checksum *3A packet checksum




    Q. How is the checksum calculated in NMEA 0183?
    A. The checksum is the 8-bit exclusive OR (no start or stop bits) of all characters in the sentence, including the "," delimiters, between -- but not including -- the "$" and "*" delimiters.
    The hexadecimal value of the most significant and least significant 4 bits of the result are converted to two ASCII characters (0-9, A-F) for transmission. The most significant character is transmitted first.
    Below is the Visual Basic code to calculate the checksum value for the NMEA sentence
    Private Function GetChecksum(ByRef sInString As String) As String
    Dim lCurrent&, lLast&
    On Error Resume Next
    '-- We don't use the $ in the checksum
    If Mid$(sInString, 1, 1) = "$" Then
    sInString = Mid$(sInString, 2)
    End If
    '-- Get the ASC of the first Char
    lLast& = Asc(Mid$(sInString, 1, 1))
    '-- Use a loop to Xor through the string
    For lCurrent& = 2 To Len(sInString)
    lLast& = lLast& Xor Asc(Mid$(sInString, lCurrent&, 1))
    Next
    '-- Pass the data back as a string
    GetChecksum = CStr(Hex(lLast&))
    End Function

    Example in C

    char cNMEA_Checksum(char *st){
    char sum = 0;
    int i;


    i = strlen(++st) - 1; //Skip '$' e '*'


    while(i){
    sum ^= *st++;
    i--;
    }

    return sum;
    }