102 lines
4 KiB
C++
102 lines
4 KiB
C++
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/*
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* Interrupt and PWM utilities for 16 bit Timer1 on ATmega168/328
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* Original code by Jesse Tane for http://labs.ideo.com August 2008
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* Modified March 2009 by Jérôme Despatis and Jesse Tane for ATmega328 support
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* Modified June 2009 by Michael Polli and Jesse Tane to fix a bug in setPeriod() which caused the timer to stop
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*
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* This is free software. You can redistribute it and/or modify it under
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* the terms of Creative Commons Attribution 3.0 United States License.
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* To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/us/
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* or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA.
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*
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*/
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#include "TimerOne.h"
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TimerOne Timer1; // preinstatiate
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ISR(TIMER1_OVF_vect) // interrupt service routine that wraps a user defined function supplied by attachInterrupt
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{
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Timer1.isrCallback();
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}
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void TimerOne::initialize(long microseconds)
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{
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TCCR1A = 0; // clear control register A
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TCCR1B = _BV(WGM13); // set mode as phase and frequency correct pwm, stop the timer
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setPeriod(microseconds);
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}
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void TimerOne::setPeriod(long microseconds)
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{
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long cycles = (F_CPU * microseconds) / 2000000; // the counter runs backwards after TOP, interrupt is at BOTTOM so divide microseconds by 2
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if(cycles < RESOLUTION) clockSelectBits = _BV(CS10); // no prescale, full xtal
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else if((cycles >>= 3) < RESOLUTION) clockSelectBits = _BV(CS11); // prescale by /8
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else if((cycles >>= 3) < RESOLUTION) clockSelectBits = _BV(CS11) | _BV(CS10); // prescale by /64
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else if((cycles >>= 2) < RESOLUTION) clockSelectBits = _BV(CS12); // prescale by /256
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else if((cycles >>= 2) < RESOLUTION) clockSelectBits = _BV(CS12) | _BV(CS10); // prescale by /1024
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else cycles = RESOLUTION - 1, clockSelectBits = _BV(CS12) | _BV(CS10); // request was out of bounds, set as maximum
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ICR1 = pwmPeriod = cycles; // ICR1 is TOP in p & f correct pwm mode
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TCCR1B &= ~(_BV(CS10) | _BV(CS11) | _BV(CS12));
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TCCR1B |= clockSelectBits; // reset clock select register
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}
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void TimerOne::setPwmDuty(char pin, int duty)
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{
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unsigned long dutyCycle = pwmPeriod;
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dutyCycle *= duty;
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dutyCycle >>= 10;
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if(pin == 1 || pin == 9) OCR1A = dutyCycle;
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else if(pin == 2 || pin == 10) OCR1B = dutyCycle;
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}
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void TimerOne::pwm(char pin, int duty, long microseconds) // expects duty cycle to be 10 bit (1024)
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{
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if(microseconds > 0) setPeriod(microseconds);
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if(pin == 1 || pin == 9) {
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DDRB |= _BV(PORTB1); // sets data direction register for pwm output pin
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TCCR1A |= _BV(COM1A1); // activates the output pin
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}
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else if(pin == 2 || pin == 10) {
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DDRB |= _BV(PORTB2);
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TCCR1A |= _BV(COM1B1);
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}
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setPwmDuty(pin, duty);
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start();
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}
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void TimerOne::disablePwm(char pin)
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{
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if(pin == 1 || pin == 9) TCCR1A &= ~_BV(COM1A1); // clear the bit that enables pwm on PB1
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else if(pin == 2 || pin == 10) TCCR1A &= ~_BV(COM1B1); // clear the bit that enables pwm on PB2
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}
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void TimerOne::attachInterrupt(void (*isr)(), long microseconds)
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{
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if(microseconds > 0) setPeriod(microseconds);
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isrCallback = isr; // register the user's callback with the real ISR
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TIMSK1 = _BV(TOIE1); // sets the timer overflow interrupt enable bit
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sei(); // ensures that interrupts are globally enabled
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start();
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}
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void TimerOne::detachInterrupt()
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{
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TIMSK1 &= ~_BV(TOIE1); // clears the timer overflow interrupt enable bit
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}
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void TimerOne::start()
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{
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TCCR1B |= clockSelectBits;
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}
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void TimerOne::stop()
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{
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TCCR1B &= ~(_BV(CS10) | _BV(CS11) | _BV(CS12)); // clears all clock selects bits
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}
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void TimerOne::restart()
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{
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TCNT1 = 0;
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}
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