diff options
| -rw-r--r-- | cores/arduino/WInterrupts.c | 12 | ||||
| -rw-r--r-- | cores/arduino/wiring.c | 151 |
2 files changed, 123 insertions, 40 deletions
diff --git a/cores/arduino/WInterrupts.c b/cores/arduino/WInterrupts.c index d3fbf10..6663462 100644 --- a/cores/arduino/WInterrupts.c +++ b/cores/arduino/WInterrupts.c @@ -223,6 +223,18 @@ void detachInterrupt(uint8_t interruptNum) { #warning detachInterrupt may need some more work for this cpu (case 1) #endif break; + + case 2: + #if defined(EIMSK) && defined(INT2) + EIMSK &= ~(1 << INT2); + #elif defined(GICR) && defined(INT2) + GICR &= ~(1 << INT2); // atmega32 + #elif defined(GIMSK) && defined(INT2) + GIMSK &= ~(1 << INT2); + #else + #warning detachInterrupt may need some more work for this cpu (case 2) + #endif + break; #endif } diff --git a/cores/arduino/wiring.c b/cores/arduino/wiring.c index 5cbe241..6cb22c0 100644 --- a/cores/arduino/wiring.c +++ b/cores/arduino/wiring.c @@ -92,7 +92,6 @@ unsigned long micros() { #error TIMER 0 not defined #endif - #ifdef TIFR0 if ((TIFR0 & _BV(TOV0)) && (t < 255)) m++; @@ -119,65 +118,118 @@ void delay(unsigned long ms) } } -/* Delay for the given number of microseconds. Assumes a 8 or 16 MHz clock. */ +/* Delay for the given number of microseconds. Assumes a 1, 8, 12, 16, 20 or 24 MHz clock. */ void delayMicroseconds(unsigned int us) { + // call = 4 cycles + 2 to 4 cycles to init us(2 for constant delay, 4 for variable) + // 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 +#if F_CPU >= 24000000L + // for the 24 MHz clock for the aventurous ones, trying to overclock + + // zero delay fix + if (!us) return; // = 3 cycles, (4 when true) + + // the following loop takes a 1/6 of a microsecond (4 cycles) + // per iteration, so execute it six times for each microsecond of + // delay requested. + us *= 6; // x6 us, = 7 cycles + + // account for the time taken in the preceeding commands. + // we just burned 22 (24) cycles above, remove 5, (5*4=20) + // us is at least 6 so we can substract 5 + us -= 5; //=2 cycles + +#elif F_CPU >= 20000000L // for the 20 MHz clock on rare Arduino boards - // 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. + // for a one-microsecond delay, simply return. the overhead + // of the function call takes 18 (20) cycles, which is 1us __asm__ __volatile__ ( "nop" "\n\t" - "nop"); //just waiting 2 cycle - if (--us == 0) - return; + "nop" "\n\t" + "nop" "\n\t" + "nop"); //just waiting 4 cycles + if (us <= 1) return; // = 3 cycles, (4 when true) // 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 + us = (us << 2) + us; // x5 us, = 7 cycles // account for the time taken in the preceeding commands. - us -= 2; + // we just burned 26 (28) cycles above, remove 7, (7*4=28) + // us is at least 10 so we can substract 7 + us -= 7; // 2 cycles #elif F_CPU >= 16000000L // for the 16 MHz clock on most Arduino boards // for a one-microsecond delay, simply return. the overhead - // of the function call yields a delay of approximately 1 1/8 us. - if (--us == 0) - return; + // of the function call takes 14 (16) cycles, which is 1us + if (us <= 1) return; // = 3 cycles, (4 when true) - // the following loop takes a quarter of a microsecond (4 cycles) + // the following loop takes 1/4 of a microsecond (4 cycles) // per iteration, so execute it four times for each microsecond of // delay requested. - us <<= 2; + us <<= 2; // x4 us, = 4 cycles // account for the time taken in the preceeding commands. - us -= 2; -#else - // for the 8 MHz internal clock on the ATmega168 + // we just burned 19 (21) cycles above, remove 5, (5*4=20) + // us is at least 8 so we can substract 5 + us -= 5; // = 2 cycles, + +#elif F_CPU >= 12000000L + // for the 12 MHz clock if somebody is working with USB + + // for a 1 microsecond delay, simply return. the overhead + // of the function call takes 14 (16) cycles, which is 1.5us + if (us <= 1) return; // = 3 cycles, (4 when true) - // for a one- or two-microsecond delay, simply return. the overhead of - // the function calls takes more than two microseconds. can't just - // subtract two, since us is unsigned; we'd overflow. - if (--us == 0) - return; - if (--us == 0) - return; + // the following loop takes 1/3 of a microsecond (4 cycles) + // per iteration, so execute it three times for each microsecond of + // delay requested. + us = (us << 1) + us; // x3 us, = 5 cycles + + // account for the time taken in the preceeding commands. + // we just burned 20 (22) cycles above, remove 5, (5*4=20) + // us is at least 6 so we can substract 5 + us -= 5; //2 cycles + +#elif F_CPU >= 8000000L + // for the 8 MHz internal clock - // the following loop takes half of a microsecond (4 cycles) + // for a 1 and 2 microsecond delay, simply return. the overhead + // of the function call takes 14 (16) cycles, which is 2us + if (us <= 2) return; // = 3 cycles, (4 when true) + + // the following loop takes 1/2 of a microsecond (4 cycles) // per iteration, so execute it twice for each microsecond of // delay requested. - us <<= 1; - - // partially compensate for the time taken by the preceeding commands. - // we can't subtract any more than this or we'd overflow w/ small delays. - us--; + us <<= 1; //x2 us, = 2 cycles + + // account for the time taken in the preceeding commands. + // we just burned 17 (19) cycles above, remove 4, (4*4=16) + // us is at least 6 so we can substract 4 + us -= 4; // = 2 cycles + +#else + // for the 1 MHz internal clock (default settings for common Atmega microcontrollers) + + // the overhead of the function calls is 14 (16) cycles + if (us <= 16) return; //= 3 cycles, (4 when true) + if (us <= 25) return; //= 3 cycles, (4 when true), (must be at least 25 if we want to substract 22) + + // compensate for the time taken by the preceeding and next commands (about 22 cycles) + us -= 22; // = 2 cycles + // the following loop takes 4 microseconds (4 cycles) + // per iteration, so execute it us/4 times + // us is at least 4, divided by 4 gives us 1 (no zero delay bug) + us >>= 2; // us div 4, = 4 cycles + + #endif // busy wait @@ -185,6 +237,7 @@ void delayMicroseconds(unsigned int us) "1: sbiw %0,1" "\n\t" // 2 cycles "brne 1b" : "=w" (us) : "0" (us) // 2 cycles ); + // return = 4 cycles } void init() @@ -199,7 +252,7 @@ void init() #if defined(TCCR0A) && defined(WGM01) sbi(TCCR0A, WGM01); sbi(TCCR0A, WGM00); -#endif +#endif // set timer 0 prescale factor to 64 #if defined(__AVR_ATmega128__) @@ -302,14 +355,32 @@ void init() #endif #if defined(ADCSRA) - // set a2d prescale factor to 128 - // 16 MHz / 128 = 125 KHz, inside the desired 50-200 KHz range. - // XXX: this will not work properly for other clock speeds, and - // this code should use F_CPU to determine the prescale factor. - sbi(ADCSRA, ADPS2); - sbi(ADCSRA, ADPS1); - sbi(ADCSRA, ADPS0); - + // set a2d prescaler so we are inside the desired 50-200 KHz range. + #if F_CPU >= 16000000 // 16 MHz / 128 = 125 KHz + sbi(ADCSRA, ADPS2); + sbi(ADCSRA, ADPS1); + sbi(ADCSRA, ADPS0); + #elif F_CPU >= 8000000 // 8 MHz / 64 = 125 KHz + sbi(ADCSRA, ADPS2); + sbi(ADCSRA, ADPS1); + cbi(ADCSRA, ADPS0); + #elif F_CPU >= 4000000 // 4 MHz / 32 = 125 KHz + sbi(ADCSRA, ADPS2); + cbi(ADCSRA, ADPS1); + sbi(ADCSRA, ADPS0); + #elif F_CPU >= 2000000 // 2 MHz / 16 = 125 KHz + sbi(ADCSRA, ADPS2); + cbi(ADCSRA, ADPS1); + cbi(ADCSRA, ADPS0); + #elif F_CPU >= 1000000 // 1 MHz / 8 = 125 KHz + cbi(ADCSRA, ADPS2); + sbi(ADCSRA, ADPS1); + sbi(ADCSRA, ADPS0); + #else // 128 kHz / 2 = 64 KHz -> This is the closest you can get, the prescaler is 2 + cbi(ADCSRA, ADPS2); + cbi(ADCSRA, ADPS1); + sbi(ADCSRA, ADPS0); + #endif // enable a2d conversions sbi(ADCSRA, ADEN); #endif |