103 lines
4.1 KiB
C++
103 lines
4.1 KiB
C++
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/*
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* Interrupt and PWM utilities for 16 bit Timer3 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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* Modified Oct 2009 by Dan Clemens to work with timer3 of the ATMega1280 or Arduino Mega
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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 "TimerThree.h"
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TimerThree Timer3; // preinstatiate
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ISR(TIMER3_OVF_vect) // interrupt service routine that wraps a user defined function supplied by attachInterrupt
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{
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Timer3.isrCallback();
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}
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void TimerThree::initialize(long microseconds)
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{
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TCCR3A = 0; // clear control register A
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TCCR3B = _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 TimerThree::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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ICR3 = pwmPeriod = cycles; // ICR1 is TOP in p & f correct pwm mode
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TCCR3B &= ~(_BV(CS10) | _BV(CS11) | _BV(CS12));
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TCCR3B |= clockSelectBits; // reset clock select register
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}
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void TimerThree::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 == 5) OCR3A = dutyCycle;
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if(pin == 2) OCR3B = dutyCycle;
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if(pin == 3) OCR3C = dutyCycle;
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}
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void TimerThree::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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// sets data direction register for pwm output pin
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// activates the output pin
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if(pin == 5) { DDRE |= _BV(PORTE3); TCCR3A |= _BV(COM3A1); }
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if(pin == 2) { DDRE |= _BV(PORTE4); TCCR3A |= _BV(COM3B1); }
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if(pin == 3) { DDRE |= _BV(PORTE5); TCCR3A |= _BV(COM3C1); }
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setPwmDuty(pin, duty);
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start();
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}
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void TimerThree::disablePwm(char pin)
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{
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if(pin == 5) TCCR3A &= ~_BV(COM3A1); // clear the bit that enables pwm on PE3
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if(pin == 2) TCCR3A &= ~_BV(COM3B1); // clear the bit that enables pwm on PE4
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if(pin == 3) TCCR3A &= ~_BV(COM3C1); // clear the bit that enables pwm on PE5
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}
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void TimerThree::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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TIMSK3 = _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 TimerThree::detachInterrupt()
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{
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TIMSK3 &= ~_BV(TOIE1); // clears the timer overflow interrupt enable bit
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}
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void TimerThree::start()
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{
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TCCR3B |= clockSelectBits;
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}
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void TimerThree::stop()
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{
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TCCR3B &= ~(_BV(CS10) | _BV(CS11) | _BV(CS12)); // clears all clock selects bits
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}
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void TimerThree::restart()
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{
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TCNT3 = 0;
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}
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