how can i use 3 timers on a MEGA2560?
i found a library for timer1 and for timer3:
http://www.arduino.cc/playground/Code/Timer1
but i need 3 timers! do i have to modify the timer3 library to access more timers? if yes, how do i do this?
what is the difference between the timer1 and the timer3 library? can i use them both in the same way?
i need the 3 timers to control 3 Steppers accurate with Interrupts.
i need the 3 timers to control 3 Steppers accurate with Interrupts.
It's not clear what the interrupts are doing. What defines how to position the three stepper motors. Are they all supposed to reach new settings in the same period of time, though requiring different numbers of steps?
each stepper will be controlled by a driver. the driver needs a digital signal for each step. the signal will be generated bu an interrupt, that will be attached to a timer. all tree steppers have to do different speeds at the same time, so i need 3 timers, to attach 3 interrupts to set 3 digital pins high or low to control 3 drivers that will control 3 steppers.
but this part of my program already works fine. i just don't know how to access the 3 timers.
here is the code of the timer3 library. can i just change every 3 to a 4 and it will work for timer 4? which other things to i have to change?
/*
* 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 J?©r?¥me 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;
}
the driver needs a digital signal for each step. the signal will be generated bu an interrupt, that will be attached to a timer.
I guess that I am failing to see why the signal is to be generated in an interrupt, or why one timer can't be used for all three signals.
here is the code of the timer3 library. can i just change every 3 to a 4 and it will work for timer 4? which other things to i have to change?
Beats me.
if the signal is generated without a timer interrupt it will never be on time, because the right moment to set the pin high is while something else is happening in the program. am lost a lot of steps like that.
i could do it with just one timer, where i attach 3 interrupts, but this is complicated.
or how would you do that?