File content as of revision 0:ee556de472a9:

#include "mbed.h"
#include "m3pi.h"

m3pi m3pi;

enum State {RUN, ROTATE};

int main() {
    float speed = 0.2;
    float correction = 0.05;   
    int threshold = 500;
    float turn30 = 0.2;

    int sens[5]; //left, sub-l, center, sub-r, right
    State state = RUN;
        
    m3pi.cls();
    m3pi.locate(0,0);
    m3pi.printf("Line");
    m3pi.locate(0,1);
    m3pi.printf("  Tracer");

    wait(2.0);
    
    m3pi.sensor_auto_calibrate();

    
    while(1) {
        m3pi.putc(0x87); //get values of calibrated sensors (0-1000)
        for(int i=0; i < 5; ++i) {
            sens[i] = m3pi.getc();
            sens[i] += m3pi.getc() << 8;
        }

        switch(state) {
        case RUN:
            /* Turn left (over 30deg.) */
            if(sens[0] > threshold ||
               sens[2] <= threshold && sens[1] <= threshold && sens[3] <= threshold) {
                m3pi.stop();
                wait(0.1);
                m3pi.left(speed);
                wait(turn30);
                m3pi.stop();
            
                state = ROTATE;
            }
            /* Go forward */
            else {
                if(sens[2] > threshold) {  // Go straight
                  m3pi.forward(speed);
                } else if(sens[1] > threshold) { //Correction (left)
                    m3pi.left_motor(speed - correction);
                } else { //Correction (right)
                    m3pi.right_motor(speed - correction);
                }
            }
            break;
        case ROTATE: // Rotate clockwise and find a road
            if(sens[2] > threshold) {
                m3pi.stop();
                state = RUN;
            }
            m3pi.right(speed);
            break;
        }
    }
}