[Arduino UNO] Unable to use another timer instead of Timer0 for OSEK's Counters

[thegabriele97]

Hi, I would like to use another timer for a personalized counter instead of the predefined one (SystemCounter). I aimed to use Timer 2, but is impossible to set it from the OIL file like

COUNTER MyCounter {
  SOURCE = TIMER2_OVF;
  TICKSPERBASE = 6250;
  MAXALLOWEDVALUE = 6250;
  MINCYCLE = 1;
};

The idea was to use the entire 16 Mhz internal clock without no prescalar, in order to have a 16 us period between an overflow interrupt and the next one. Multiplying by 6250 I can have alarms associated to MyCounter of 100 ms or multiple of this value.

But when I try to compile the oil file using GOIL, I get an error saying that source can be only "Timer0_OVF, PIN1, PIN2". How I can use timer 2?

Another strange thing is that if i put source = timer0_ovf (like the default definition of SystemCounter), in the generated .c code I see an ISR(TIMER0_OVF). _I think this is actually incorrect because the ISR associated with the timer0 overflow is TIMER0_OVFvect, so it wouldn't work anyway. How SystemCounter works actually?

Thank you

[thegabriele97]

This is how my setup() function actually looks like:

void setup() {
#ifdef DEBUG
    Serial.begin(SERIAL_BAUDRATE);
#endif

    Serial.begin(SERIAL_BAUDRATE);

    // Setting timer0 to 0
    TCNT2 = 0x00;

    // Setting TOIE in order to enable interrupt
    TIMSK2 |= 0x1;

    // Clearing timer 2 configuration registers A and B
    TCCR2A &= 0x00;
    TCCR2B &= 0x00;

    // Setting scalar to 1: CS02, CS01, CS00 = 0b001
    TCCR2B |= 0x01;

    /*
     * Now we have a Timer2 with a 16MHz clock. 
     * Ath each clock cycle, TCNT0 goes up by 1.
     * When it reaches 0xff, we have overflow and it
     * means an interrupt: this means that each interrupt
     * occurs every 16 us and in order to have a
     * counter that counts 1 every 100 ms
     * we need exactly 6250 ticks!
     */

    pinMode(MORSE_LED, OUTPUT);
    digitalWrite(MORSE_LED, LOW);
}

[mbriday]

Hi, I have just pushed a fix. You can now use TIMER0 to 2. I also added a full example (examples/avr/arduinoUno/customCounterExample/). However, using other timers may have side effect (TIM2 is used for Tone and PWM!). Regards