I would like to use three timers in CTC mode to launch three Interrupt Service Routines at different frequencies.
In this application I need to use the servo library, millis() and micros() functions.
Timer3 (Working)
Thanks to this question, Timer3 has been set up in the following way:
cli(); // disable global interrupts
TCCR3A = 0; // set entire TCCR3A register to 0
TCCR3B = 0; // same for TCCR3B
// set compare match register to desired timer count: @~744 Hz
OCR3A = 20;
// turn on CTC mode:
TCCR3B |= (1 << WGM32);
// Set CS10 and CS12 bits for 1024 prescaler:
TCCR3B |= (1 << CS30) | (1 << CS32);
// enable timer compare interrupt:
TIMSK3 |= (1 << OCIE3B);
// enable global interrupts:
sei();
ISR(TIMER3_COMPB_vect)
{
cont++;
}
Timer4 I've tried with this configuration:
cli(); // disable global interrupts
TCCR4A = 0; // set entire TCCR3A register to 0
TCCR4B = 0; // same for TCCR3B
// set compare match register to desired timer count: @ ~744 Hz
OCR4A = 20;
// turn on CTC mode:
TCCR4B |= (1 << WGM42);
// Set CS10 and CS12 bits for 1024 prescaler:
TCCR4B |= (1 << CS40) | (1 << CS42);
// enable timer compare interrupt:
TIMSK4 |= (1 << OCIE4B);
//TIMSK4 |= (1 << OCIE4A); same issue
// enable global interrupts:
sei();
ISR(TIMER4_COMPB_vect) //TIMER4_COMPA_vect same issue
{
cont++;
}
But the compiler returns an error caused by the servo library conflict:
Servo\Servo.cpp.o: In function '__vector_42': C:\Program Files (x86)\Arduino\libraries\Servo/Servo.cpp:117: multiple definition of '__vector_42' Timer4B_800Hz.cpp.o:C:\Program Files (x86)\Arduino/Timer4B_800Hz.ino:49: first defined here c:/program files (x86)/arduino/hardware/tools/avr/bin/../lib/gcc/avr/4.3.2/../../../../avr/bin/ld.exe: Disabling relaxation: it will not work with multiple definitions
As Gerben suggested in a comment in this question:
They are just hogging all timers. I guess you have to alter the library slightly by removing the #define _useTimer3 line, or try putting a #undef _useTimer3 right after the include. – Gerben
I would avoid changing the servo library since motors play a critcal role in the application.
Timer 5 Same issue
Which timers and output compare registers can I use to set up the three ISR correctly?