void set_frequency( int frequency );
void tick();
// For some reason this can't go in the .cpp, see : http://mbed.org/forum/mbed/topic/2774/?page=1#comment-14221
void set_frequency( int frequency );
void tick();
// For some reason this can't go in the .cpp, see : http://mbed.org/forum/mbed/topic/2774/?page=1#comment-14221