Re: [avr-gcc-list] Problem with timing

[Bjarne Laursen]

This code works for me.

int16_t GetTimer10Ms(void)
{
    int16_t s;
    cli();
    s=timer10ms;   // timer10ms is incremented in interrupt
    sei();
    return s;
}

void Wait10Ms(int16_t ms10)
{
    ms10+= GetTimer10Ms();
    while (GetTimer10Ms()-ms10 <0)
    {
        wdt_reset();
    }
}





At 21:18 03-02-2004, you wrote:
> Where is ms_timer set and reset to 0?  Shouldn't your code be:
>
>         while( ms_timer < koniec );
>         ms_timer = 0 ;
> }
>
> Keith
>
>
> On Tue, 3 Feb 2004, Juraj wrote:
>
> > Hi all..
> >
> > Perhaps, it is trivial problem, but I cannot find the bug.
> > Please help.
> >
> > I have LED, connected to AVR. I want to get blinking LED, with 1:1
> > alternation:
> > LED_ON - 500ms delay - LED_OFF - 500ms delay - LED_ON ...
> >
> > Problem is - times are not always 500ms, some of periodes are shorter.
> >
> >
> > Thank you very much.
> >
> > Juraj.
> >
> >
> >
> >
> >
> >
> >
> >
> > So here is part of main programm:
> >
> > #include "timer.h"
> >
> > int main(void) {
> > .
> > .
> >       timer0_init();
> >       while(1){
> >               LED_ON;         //sets the output
> >               ms_delay(500);
> >               LED_OFF;        //clears the output
> >               ms_delay(500);
> >       }
> > .
> > .
> > }
> >
> >
> > 
> *******************************************************************************************
> >
> > And here is timing module - timer.c:
> >
> > #include <avr/timer.h>
> > #include <avr/interrupt.h>
> > #include <avr/signal.h>
> > #include <inttypes.h>
> > #include "casovac.h"
> >
> > volatile uint32_t ms_timer = 0;
> >
> >
> > void timer0_init(void)
> > {
> >       timer_enable_int( BV(TOIE0) );
> >       timer0_source(CK64);
> >       TCNT0 = PRESCALE_LO;
> > }
> >
> >
> > SIGNAL(SIG_OVERFLOW0)                  // signal handler for tcnt0
> > overflow interrupt
> > {
> >       ms_timer++;                    // increment timer counter
> >       TCNT0 = PRESCALE_LO;
> > }
> >
> >
> > void ms_delay(uint16_t ms )
> > {
> > uint32_t koniec = ms_timer + (uint32_t)ms;
> >
> >       while( ms_timer < koniec );
> > }
> >
> > 
> *******************************************************************************************
> >
> > And timer.h:
> >
> > #define       F_CPU           8000000
> > #define       PRESCALE_HI     64
> > #define       PRESCALE_LO     ( 256 - ( (F_CPU/PRESCALE_HI) / 1000 ) )
> >
> > extern volatile uint32_t ms_timer;
> >
> > void timer0_init(void);
> > void ms_delay(uint16_t ms );
> >
> > 
> *******************************************************************************************
> >
> >
> >
> >
> > --
> >
> > ----------------------------
> > email:        address@hidden
> >       address@hidden
> > http://       durec.szm.sk