diff options
Diffstat (limited to 'cores/arduino/wiring.c')
| -rw-r--r-- | cores/arduino/wiring.c | 324 |
1 files changed, 324 insertions, 0 deletions
diff --git a/cores/arduino/wiring.c b/cores/arduino/wiring.c new file mode 100644 index 0000000..ac8bb6f --- /dev/null +++ b/cores/arduino/wiring.c @@ -0,0 +1,324 @@ +/* + wiring.c - Partial implementation of the Wiring API for the ATmega8. + Part of Arduino - http://www.arduino.cc/ + + Copyright (c) 2005-2006 David A. Mellis + + This library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + This library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General + Public License along with this library; if not, write to the + Free Software Foundation, Inc., 59 Temple Place, Suite 330, + Boston, MA 02111-1307 USA + + $Id$ +*/ + +#include "wiring_private.h" + +// the prescaler is set so that timer0 ticks every 64 clock cycles, and the +// the overflow handler is called every 256 ticks. +#define MICROSECONDS_PER_TIMER0_OVERFLOW (clockCyclesToMicroseconds(64 * 256)) + +// the whole number of milliseconds per timer0 overflow +#define MILLIS_INC (MICROSECONDS_PER_TIMER0_OVERFLOW / 1000) + +// the fractional number of milliseconds per timer0 overflow. we shift right +// by three to fit these numbers into a byte. (for the clock speeds we care +// about - 8 and 16 MHz - this doesn't lose precision.) +#define FRACT_INC ((MICROSECONDS_PER_TIMER0_OVERFLOW % 1000) >> 3) +#define FRACT_MAX (1000 >> 3) + +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) + unsigned long m = timer0_millis; + unsigned char f = timer0_fract; + + m += MILLIS_INC; + f += FRACT_INC; + if (f >= FRACT_MAX) { + f -= FRACT_MAX; + m += 1; + } + + timer0_fract = f; + timer0_millis = m; + timer0_overflow_count++; +} + +unsigned long millis() +{ + unsigned long m; + uint8_t oldSREG = SREG; + + // disable interrupts while we read timer0_millis or we might get an + // inconsistent value (e.g. in the middle of a write to timer0_millis) + cli(); + m = timer0_millis; + SREG = oldSREG; + + return m; +} + +unsigned long micros() { + unsigned long m; + uint8_t oldSREG = SREG, t; + + cli(); + m = timer0_overflow_count; +#if defined(TCNT0) + t = TCNT0; +#elif defined(TCNT0L) + t = TCNT0L; +#else + #error TIMER 0 not defined +#endif + + +#ifdef TIFR0 + if ((TIFR0 & _BV(TOV0)) && (t < 255)) + m++; +#else + if ((TIFR & _BV(TOV0)) && (t < 255)) + m++; +#endif + + SREG = oldSREG; + + return ((m << 8) + t) * (64 / clockCyclesPerMicrosecond()); +} + +void delay(unsigned long ms) +{ + uint16_t start = (uint16_t)micros(); + + while (ms > 0) { + if (((uint16_t)micros() - start) >= 1000) { + ms--; + start += 1000; + } + } +} + +/* Delay for the given number of microseconds. Assumes a 8 or 16 MHz clock. */ +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 + + // 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 + // of the function call yields a delay of approximately 1 1/8 us. + if (--us == 0) + return; + + // the following loop takes a quarter of a microsecond (4 cycles) + // per iteration, so execute it four times for each microsecond of + // delay requested. + us <<= 2; + + // account for the time taken in the preceeding commands. + us -= 2; +#else + // for the 8 MHz internal clock on the ATmega168 + + // 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 half 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--; +#endif + + // busy wait + __asm__ __volatile__ ( + "1: sbiw %0,1" "\n\t" // 2 cycles + "brne 1b" : "=w" (us) : "0" (us) // 2 cycles + ); +} + +void init() +{ + // this needs to be called before setup() or some functions won't + // work there + sei(); + + // on the ATmega168, timer 0 is also used for fast hardware pwm + // (using phase-correct PWM would mean that timer 0 overflowed half as often + // resulting in different millis() behavior on the ATmega8 and ATmega168) +#if defined(TCCR0A) && defined(WGM01) + sbi(TCCR0A, WGM01); + sbi(TCCR0A, WGM00); +#endif + + // set timer 0 prescale factor to 64 +#if defined(__AVR_ATmega128__) + // CPU specific: different values for the ATmega128 + sbi(TCCR0, CS02); +#elif defined(TCCR0) && defined(CS01) && defined(CS00) + // this combination is for the standard atmega8 + sbi(TCCR0, CS01); + sbi(TCCR0, CS00); +#elif defined(TCCR0B) && defined(CS01) && defined(CS00) + // this combination is for the standard 168/328/1280/2560 + sbi(TCCR0B, CS01); + sbi(TCCR0B, CS00); +#elif defined(TCCR0A) && defined(CS01) && defined(CS00) + // this combination is for the __AVR_ATmega645__ series + sbi(TCCR0A, CS01); + sbi(TCCR0A, CS00); +#else + #error Timer 0 prescale factor 64 not set correctly +#endif + + // enable timer 0 overflow interrupt +#if defined(TIMSK) && defined(TOIE0) + sbi(TIMSK, TOIE0); +#elif defined(TIMSK0) && defined(TOIE0) + sbi(TIMSK0, TOIE0); +#else + #error Timer 0 overflow interrupt not set correctly +#endif + + // timers 1 and 2 are used for phase-correct hardware pwm + // this is better for motors as it ensures an even waveform + // note, however, that fast pwm mode can achieve a frequency of up + // 8 MHz (with a 16 MHz clock) at 50% duty cycle + +#if defined(TCCR1B) && defined(CS11) && defined(CS10) + TCCR1B = 0; + + // 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); +#elif defined(TCCR1) + #warning this needs to be finished +#endif + + // set timer 2 prescale factor to 64 +#if defined(TCCR2) && defined(CS22) + sbi(TCCR2, CS22); +#elif defined(TCCR2B) && defined(CS22) + sbi(TCCR2B, CS22); +#else + #warning Timer 2 not finished (may not be present on this CPU) +#endif + + // configure timer 2 for phase correct pwm (8-bit) +#if defined(TCCR2) && defined(WGM20) + sbi(TCCR2, WGM20); +#elif defined(TCCR2A) && defined(WGM20) + sbi(TCCR2A, WGM20); +#else + #warning Timer 2 not finished (may not be present on this CPU) +#endif + +#if defined(TCCR3B) && defined(CS31) && defined(WGM30) + sbi(TCCR3B, CS31); // set timer 3 prescale factor to 64 + sbi(TCCR3B, CS30); + sbi(TCCR3A, WGM30); // put timer 3 in 8-bit phase correct pwm mode +#endif + +#if defined(TCCR4A) && defined(TCCR4B) && defined(TCCR4D) /* beginning of timer4 block for 32U4 and similar */ + sbi(TCCR4B, CS42); // set timer4 prescale factor to 64 + sbi(TCCR4B, CS41); + sbi(TCCR4B, CS40); + sbi(TCCR4D, WGM40); // put timer 4 in phase- and frequency-correct PWM mode + sbi(TCCR4A, PWM4A); // enable PWM mode for comparator OCR4A + sbi(TCCR4C, PWM4D); // enable PWM mode for comparator OCR4D +#else /* beginning of timer4 block for ATMEGA1280 and ATMEGA2560 */ +#if defined(TCCR4B) && defined(CS41) && defined(WGM40) + sbi(TCCR4B, CS41); // set timer 4 prescale factor to 64 + sbi(TCCR4B, CS40); + sbi(TCCR4A, WGM40); // put timer 4 in 8-bit phase correct pwm mode +#endif +#endif /* end timer4 block for ATMEGA1280/2560 and similar */ + +#if defined(TCCR5B) && defined(CS51) && defined(WGM50) + sbi(TCCR5B, CS51); // set timer 5 prescale factor to 64 + sbi(TCCR5B, CS50); + sbi(TCCR5A, WGM50); // put timer 5 in 8-bit phase correct pwm mode +#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); + + // enable a2d conversions + sbi(ADCSRA, ADEN); +#endif + + // the bootloader connects pins 0 and 1 to the USART; disconnect them + // here so they can be used as normal digital i/o; they will be + // reconnected in Serial.begin() +#if defined(UCSRB) + UCSRB = 0; +#elif defined(UCSR0B) + UCSR0B = 0; +#endif +} |