nmea_checksum.c

the example file that can decode the NMEA protocol

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#include "NMEA_Lib.h"


void CalcChecksum(CHAR string[], size_t str_length, CHAR checksum[])
{
    UINT8  i;
    INT32 sum = 0;

    /* The "sentence" is from position 1 (the $) to the "*"
     * The checksum calc does NOT include the $ or *
     */
    for(i=0; i<str_length; i++)
    {
        sum ^= string[i];
    }

    /* The returned value is a 2 character string 
     * containing the check sum value 
     */
    sprintf(checksum, "%02X", sum);

    return;
} /* end CalcChecksum() */