timer.h

ATmega8实现USB接口（采用USB的CDC类

#ifndef __timer_h_included__
#define __timer_h_included__

#include <avr/io.h> /* for TCNT0 */
#include "utils.h"

extern volatile uchar   timerTimeoutCnt;
extern volatile uchar   timerLongTimeoutCnt;

/* ------------------------------------------------------------------------- */

#define TIMER_TICK_US       5.33333333333333333333

void timerMsDelay(uchar ms);    /* 1 ms precision, based on hardware timer */
void timerSetupTimeout(uchar msDuration);

#define TIMER_US_DELAY(us)  timerTicksDelay((uchar)((us)/TIMER_TICK_US))

/* ------------------------------------------------------------------------- */

static inline void timerTicksDelay(uchar ticks)
{
char    d, until = TCNT0 + ticks;

    do{
        d = TCNT0 - until;  /* enforce 8 bit arithmetics */
    }while(d < 0);
}

static inline uchar   timerTimeoutOccurred(void)
{
    return timerTimeoutCnt == 0;
}

static inline void    timerSetupLongTimeout(uchar ms100Duration)
{
    timerLongTimeoutCnt = ms100Duration;
}

static inline uchar   timerLongTimeoutOccurred(void)
{
    return timerLongTimeoutCnt == 0;
}

/* ------------------------------------------------------------------------- */

#endif /* __timer_h_included__ */