void init_timers () {
// We use the 8 bit timer to generate the polling interrupt for notes.
// It should interrupt often, like every 50 microseconds.
TCCR0A = (1 << WGM01); // mode 010: CTC
#if CPU_MHZ==4
TCCR0B = 1 << CS00; // clock select 001: no prescaling
OCR0A = CPU_MHZ * POLLTIME_USEC;
#elif CPU_MHZ==8
TCCR0B = 1 << CS01; // clock select 010: clk/8 prescaling
OCR0A = CPU_MHZ/8 * POLLTIME_USEC;
#else
unusual frequency
#endif
// We use the 16 bit timer both for timing scores from the interrupt routine
// and doing mainline code waits. It interrupts once a millisecond.
TCCR1A = 0; // mode 0100: CTC
TCCR1B = (1 << WGM12) | (1<<CS10); // clock select 001: no prescaling
OCR1A = CPU_MHZ * 1000;
tune_playing = false;
scorewait_interrupt_count = 0;
delaywait_interrupt_count = 0;
TIMSK =(1<<OCIE0A) | (1<<OCIE1A); // turn on match A interrupts for both timers
Interrupts(); // enable interrupts
}
void tune_delay (unsigned duration) {
boolean notdone;
delaywait_interrupt_count = duration;
do {
// wait until the interrupt routines decrements the toggle count to zero
noInterrupts();
notdone = delaywait_interrupt_count != 0; /* interrupt-safe test */
Interrupts();
} while (notdone);
}
void delay_us(uint16_t us)
{
uint32_t systick = SysTick->VAL;
uint16_t count;
if(count == 0)return;
count = us * 9;
if(count>SysTickOverFlowValue - 1)count = SysTickOverFlowValue-1;
noInterrupts();
if(systick < count)
{
count = ((SysTickOverFlowValue-5) + systick - count);///
while(SysTick->VAL <= count)
{
;
}
if(count == 0)
count = 1;
while(SysTick->VAL > count)
{
;
}
millisSeconds++;//矫正毫秒计数
}
else
{
count = systick - count;
if(count == 0)
count = 1;
while(SysTick->VAL > count)
{
;
}
}
Interrupts();
}
