NMEA 0183 - C Implementation of Checksum Generation

C Implementation of Checksum Generation

Persons looking to implement NMEA 0183 are often stumped by the checksum part. The following C code generates a checksum for the string entered as "mystring" and prints it to the output stream. In the example a sentence for the sample file is used.

#include #include int main { char *mystring= "GPRMC,092751.000,A,5321.6802,N,00630.3371,W,0.06,31.66,280511,,,A"; int lengthofstring = strlen(mystring); int checksum=0, i; for( i=0; i
Which can be simplified to function form as follows:

#include #include int checksum(char *s) { int c = 0; while(*s) c ^= *s++; return c; } int main { char mystring = "GPRMC,092751.000,A,5321.6802,N,00630.3371,W,0.06,31.66,280511,,,A"; printf("String: %s\nChecksum: 0x%02X\n", mystring, checksum(mystring)); return 0; }

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