NMEA Checksum

NMEA Checksum calcuation

Description

NMEA Checksum calculation function

• MATLAB release: MATLAB 7.0.4 (R14SP2)

[Duane Hanselman]

FYI: No need to download, here is what is in the file:
%function checksum = CreateNMEAChecksum(NMEA_String)
function checksum = nmeachecksum(NMEA_String)

checksum = 0; %vynulování promìnné

% see if string contains the * which starts the checksum and keep string
% upto * for generating checksum
NMEA_String = strtok(NMEA_String,'*');

NMEA_String_d = double(NMEA_String); % convert characters in string to double values
for count = 2:length(NMEA_String) % checksum calculation ignores $ at start
    checksum = bitxor(checksum,NMEA_String_d(count)); % checksum calculation
    checksum = uint16(checksum); % make sure that checksum is unsigned int16
end

% convert checksum to hex value
checksum = double(checksum);
checksum = dec2hex(checksum);

% add leading zero to checksum if it is a single digit, e.g. 4 has a 0
% added so that the checksum is 04
if length(checksum) == 1
    checksum = strcat('0',checksum);
end

[jim gardiner]

does exactly what i was after. saved me a job, cheers...

[Liffa Funkel]

Exactly what i needed. Thanx

[Michael T]

Does exactly what it says - calculates NMEA checksums.

[Vince C]

I have downloaded the .M (size = 0.9KB) file then I double click on the icon and Microsoft XP says it can not open file ....

I take it that I need mathlab and this is not an .exe file ......

help

Vince

[Ajay]

This is just great. Any idea how to read strings from a text file. The strings look like
$GPGGA,123531,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47'