#ifndef _TIMER_H#define _TIMER_H/* updates 18.2 times per second */externvolatileuint32_tticks;voidtimer_init();voidtimer_free();/* countdown clock */voidtimer_start(uint8_tsecs,uint8_t*updated);uint8_ttimer_value();voidtimer_stop();voidtimer_resume();#endif /* _TIMER_H */