serial read with statemachine.

serialread.c

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

/* On Linux systems you might need to run the following command first to
 * stop the system buffering until a newline:
 * stty -icanon
 */

void main (){
        char NMEA_string[70] = "";
        char buffer = 0;
        int n = 0;
        int state = 0;

        while (1){
                //buffer = Serial.read(); // Read Character
                buffer = getchar();
                printf(" > Got %c (%d)\n",buffer,state);

                switch(state){
                        case 0: // Waiting for a $
                                if (buffer == '$'){
                                        state=1;
                                        n=0;
                                        memset(NMEA_string,0,70); // Clear NMEA_string
                                }
                        break;
                        case 1: // Got a string
                                if ((buffer=='\r') || (buffer == '\n')){ // End of string
                                        // Parse the string
                                        printf("Got String: %s\n", NMEA_string);
                                        state=0;
                                } else {
                                        NMEA_string[n++]=buffer;
                                }
                                if (n >=68) { // Stop at 68 (69 chars) so there's still a NULL at the end.
                                        printf("Error: NMEA_string has overflown (%s)\n", NMEA_string);
                                        state=0;
                                }
                        break;
                        default:
                                printf("Error: Bad state %d\n",state);
                                state=0;
                        break;
                } // Close switch
        } // Close while
}