diff options
Diffstat (limited to 'cores/arduino/wiring.c')
| -rwxr-xr-x | cores/arduino/wiring.c | 28 |
1 files changed, 27 insertions, 1 deletions
diff --git a/cores/arduino/wiring.c b/cores/arduino/wiring.c index ce4cad6..e7f7cde 100755 --- a/cores/arduino/wiring.c +++ b/cores/arduino/wiring.c @@ -41,7 +41,11 @@ volatile unsigned long timer0_overflow_count = 0; volatile unsigned long timer0_millis = 0; static unsigned char timer0_fract = 0; +#if defined(__AVR_ATtiny24__) || defined(__AVR_ATtiny44__) || defined(__AVR_ATtiny84__) +SIGNAL(TIM0_OVF_vect) +#else SIGNAL(TIMER0_OVF_vect) +#endif { // copy these to local variables so they can be stored in registers // (volatile variables must be read from memory on every access) @@ -120,8 +124,26 @@ void delayMicroseconds(unsigned int us) // calling avrlib's delay_us() function with low values (e.g. 1 or // 2 microseconds) gives delays longer than desired. //delay_us(us); +#if F_CPU >= 20000000L + // for the 20 MHz clock on rare Arduino boards -#if F_CPU >= 16000000L + // for a one-microsecond delay, simply wait 2 cycle and return. The overhead + // of the function call yields a delay of exactly a one microsecond. + __asm__ __volatile__ ( + "nop" "\n\t" + "nop"); //just waiting 2 cycle + if (--us == 0) + return; + + // the following loop takes a 1/5 of a microsecond (4 cycles) + // per iteration, so execute it five times for each microsecond of + // delay requested. + us = (us<<2) + us; // x5 us + + // account for the time taken in the preceeding commands. + us -= 2; + +#elif F_CPU >= 16000000L // for the 16 MHz clock on most Arduino boards // for a one-microsecond delay, simply return. the overhead @@ -217,11 +239,15 @@ void init() // set timer 1 prescale factor to 64 sbi(TCCR1B, CS11); +#if F_CPU >= 8000000L sbi(TCCR1B, CS10); +#endif #elif defined(TCCR1) && defined(CS11) && defined(CS10) sbi(TCCR1, CS11); +#if F_CPU >= 8000000L sbi(TCCR1, CS10); #endif +#endif // put timer 1 in 8-bit phase correct pwm mode #if defined(TCCR1A) && defined(WGM10) sbi(TCCR1A, WGM10); |