File content as of revision 0:f0345f20337e:

#include "mbed.h"
 
DigitalOut led1(LED1);
DigitalOut led2(LED2);
DigitalOut led3(LED3);

DigitalOut red(p23);
DigitalOut green(p24);
DigitalOut blue(p25);
 
class StopLight {
private:
    EventQueue _queue;
    int _pending;
 
    enum state { RED, GREEN, YELLOW };
 
    // The _step function is a traditional FSM which enqueues transitions onto the event queue
    void _step(state transition) {
        switch (transition) {
            case RED:
                set_red();
                _pending = _queue.call_in(1000, this, &StopLight::_step, GREEN);
                break;
 
            case GREEN:
                set_green();
                _pending = _queue.call_in(1000, this, &StopLight::_step, YELLOW);
                break;
 
            case YELLOW:
                set_yellow();
                _pending = _queue.call_in(500, this, &StopLight::_step, RED);
                break;
        }
    }
    void set_red(){
        red = 0; green = 1; blue = 1;
    }
    void set_green(){
        red = 1; green = 0; blue = 1;
    }
    void set_yellow() {
        red = 0; green = 0; blue = 1;
    }
public:
    // The fire function can immediately change states in the FSM
    void fire() {
        _queue.cancel(_pending);
        _queue.call(this, &StopLight::_step, GREEN);
        _queue.dispatch();
    }
};
 
StopLight sl;
 
int main (void) {
    sl.fire();
    wait(osWaitForever);
}