103 lines
4.1 KiB
C++
103 lines
4.1 KiB
C++
/*
|
|
* Interrupt and PWM utilities for 16 bit Timer3 on ATmega168/328
|
|
* Original code by Jesse Tane for http://labs.ideo.com August 2008
|
|
* Modified March 2009 by Jérôme Despatis and Jesse Tane for ATmega328 support
|
|
* Modified June 2009 by Michael Polli and Jesse Tane to fix a bug in setPeriod() which caused the timer to stop
|
|
* Modified Oct 2009 by Dan Clemens to work with timer3 of the ATMega1280 or Arduino Mega
|
|
*
|
|
* This is free software. You can redistribute it and/or modify it under
|
|
* the terms of Creative Commons Attribution 3.0 United States License.
|
|
* To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/us/
|
|
* or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA.
|
|
*
|
|
*/
|
|
|
|
#include "TimerThree.h"
|
|
|
|
TimerThree Timer3; // preinstatiate
|
|
|
|
ISR(TIMER3_OVF_vect) // interrupt service routine that wraps a user defined function supplied by attachInterrupt
|
|
{
|
|
Timer3.isrCallback();
|
|
}
|
|
|
|
void TimerThree::initialize(long microseconds)
|
|
{
|
|
TCCR3A = 0; // clear control register A
|
|
TCCR3B = _BV(WGM13); // set mode as phase and frequency correct pwm, stop the timer
|
|
setPeriod(microseconds);
|
|
}
|
|
|
|
void TimerThree::setPeriod(long microseconds)
|
|
{
|
|
long cycles = (F_CPU * microseconds) / 2000000; // the counter runs backwards after TOP, interrupt is at BOTTOM so divide microseconds by 2
|
|
if(cycles < RESOLUTION) clockSelectBits = _BV(CS10); // no prescale, full xtal
|
|
else if((cycles >>= 3) < RESOLUTION) clockSelectBits = _BV(CS11); // prescale by /8
|
|
else if((cycles >>= 3) < RESOLUTION) clockSelectBits = _BV(CS11) | _BV(CS10); // prescale by /64
|
|
else if((cycles >>= 2) < RESOLUTION) clockSelectBits = _BV(CS12); // prescale by /256
|
|
else if((cycles >>= 2) < RESOLUTION) clockSelectBits = _BV(CS12) | _BV(CS10); // prescale by /1024
|
|
else cycles = RESOLUTION - 1, clockSelectBits = _BV(CS12) | _BV(CS10); // request was out of bounds, set as maximum
|
|
ICR3 = pwmPeriod = cycles; // ICR1 is TOP in p & f correct pwm mode
|
|
TCCR3B &= ~(_BV(CS10) | _BV(CS11) | _BV(CS12));
|
|
TCCR3B |= clockSelectBits; // reset clock select register
|
|
}
|
|
|
|
void TimerThree::setPwmDuty(char pin, int duty)
|
|
{
|
|
unsigned long dutyCycle = pwmPeriod;
|
|
dutyCycle *= duty;
|
|
dutyCycle >>= 10;
|
|
if(pin == 5) OCR3A = dutyCycle;
|
|
if(pin == 2) OCR3B = dutyCycle;
|
|
if(pin == 3) OCR3C = dutyCycle;
|
|
}
|
|
|
|
void TimerThree::pwm(char pin, int duty, long microseconds) // expects duty cycle to be 10 bit (1024)
|
|
{
|
|
if(microseconds > 0) setPeriod(microseconds);
|
|
|
|
// sets data direction register for pwm output pin
|
|
// activates the output pin
|
|
if(pin == 5) { DDRE |= _BV(PORTE3); TCCR3A |= _BV(COM3A1); }
|
|
if(pin == 2) { DDRE |= _BV(PORTE4); TCCR3A |= _BV(COM3B1); }
|
|
if(pin == 3) { DDRE |= _BV(PORTE5); TCCR3A |= _BV(COM3C1); }
|
|
setPwmDuty(pin, duty);
|
|
start();
|
|
}
|
|
|
|
void TimerThree::disablePwm(char pin)
|
|
{
|
|
if(pin == 5) TCCR3A &= ~_BV(COM3A1); // clear the bit that enables pwm on PE3
|
|
if(pin == 2) TCCR3A &= ~_BV(COM3B1); // clear the bit that enables pwm on PE4
|
|
if(pin == 3) TCCR3A &= ~_BV(COM3C1); // clear the bit that enables pwm on PE5
|
|
}
|
|
|
|
void TimerThree::attachInterrupt(void (*isr)(), long microseconds)
|
|
{
|
|
if(microseconds > 0) setPeriod(microseconds);
|
|
isrCallback = isr; // register the user's callback with the real ISR
|
|
TIMSK3 = _BV(TOIE1); // sets the timer overflow interrupt enable bit
|
|
sei(); // ensures that interrupts are globally enabled
|
|
start();
|
|
}
|
|
|
|
void TimerThree::detachInterrupt()
|
|
{
|
|
TIMSK3 &= ~_BV(TOIE1); // clears the timer overflow interrupt enable bit
|
|
}
|
|
|
|
void TimerThree::start()
|
|
{
|
|
TCCR3B |= clockSelectBits;
|
|
}
|
|
|
|
void TimerThree::stop()
|
|
{
|
|
TCCR3B &= ~(_BV(CS10) | _BV(CS11) | _BV(CS12)); // clears all clock selects bits
|
|
}
|
|
|
|
void TimerThree::restart()
|
|
{
|
|
TCNT3 = 0;
|
|
}
|