Question

Please help me with this code, it is making me crazy. This is a very simple program with 8-bit timer, cycling through all 8 leds (one-by-one). Am using ATSTK600 board.

My timers are working well, I think there is some problem with the loops (when I debug this program using avr studio-gcc, I can see all the leds working as I want but when I transfer it on board…leds don’t blink). Am going crazy with this type of behavior.

Here is my code:

#include <avr/io.h>
#include <avr/interrupt.h>

volatile unsigned int intrs, i, j = 0;

void enable_ports(void);
void delay(void);

extern void __vector_23 (void) __attribute__ ((interrupt));

void enable_ports()
{
    DDRB = 0xff;

    TCCR0B = 0x03;

    TIMSK0 = 0x01;

    //TIFR0 = 0x01;

    TCNT0 = 0x00;

    //OCR0A = 61;

    intrs = 0;
}

void __vector_23 (void)
{
    for(i = 0; i<=8; i++)
    {
        while(1)
        {
            intrs++;
            if(intrs >= 61)
            {
                PORTB = (0xff<<i);
                intrs = 0;
                break;
            }

        }
    }
    PORTB = 0xff;
}

int main(void)
{
    enable_ports();
    sei();

    while(1)
    {

    }
}

Answer 1

Your interrupt routine is flawed. intrs counts only the number of times the loop has executed, not the number of timer interrupts as its name suggests. 61 iterations of that loop will take very little time. You will see nothing perceivable without an oscilloscope.

The following may be closer to what you need:

void __vector_23 (void)
{
    intrs++;
    if(intrs > 60)
    {
        intrs = 0;
        PORTB = (0xff<<i);

        i++ ;
        if(i == 8 )
        {
            i = 0 ;
            PORTB = 0xff;
        }
    }
}

Although setting the compare register OCR0A to 61 as in your commented out code would avoid the need for the interrupt counter and reduce unnecessary software overhead.