Timer2 as Timer Not Working Correctly on avr atmega32a

[maxbayne]

hiii i try to config timer2 (8bit) inside atmega32a
same configration tested over timer0 and worked perfect but when i tried it over timer2 not working

i try to generate timer every 1 second so i used count with some times to overflow the timer like i overflow timer 61 count so it mean take 1 second

i used info to calc the overflow count from this site
https://eleccelerator.com/avr-timer-calculator/

this code work fine with timer0 and generate 1 second timer but with timer2 it generates 125 ms
if i change the timer2Counter to checked with 488 it generate 1 second

why 61 working with timer0 and not working with timer2 while timer0 is same as timer2

any help plz where is the issue , i tested this with real hardware and same result

this is my code

#include "avr/interrupt.h"


int main(void)
{
  //Configuration ----------------------------------------------------


  //Config Port A as Output using some helper function
  GPIO::Port_Direction(GPIO_PORT_A,GPIO_DIRECTION_OUTPUT);
 
  //Set Timer Initial Value = 0
  TCNT2=0;

  //Set Timer Mode To Normal and Prescaler 1024
  TCCR2=0b00000101;

  //Enable Global Interrupt using register (SREG)
  BITWISE_SET_BIT(SREG,SREG_I);     //or use sei();

  //Enable Timer2 Interrupt using register (TIMSK)
  BITWISE_SET_BIT(TIMSK,TOIE2);


  //Loop ----------------------------------------------------
  while(1)
  {
     GPIO::Pin_Clear(GPIO_IO_PA1);

     delay_ms(1000);

     GPIO::Pin_Set(GPIO_IO_PA1);

     delay_ms(1000);

  }

}


int timer2Counter;
ISR(TIMER2_OVF_vect)
{
    timer2Counter++;

    //if i use 488 which (61*8) it work correct and generate 1 second timer , but if i use 61 generate 125ms this issue only with timer2 but with timer0 61 worked fine
    if(timer2Counter==61)
    {
        GPIO::Pin_Toggle(GPIO_IO_PA2);

        timer2Counter=0;
    }
    
}

 

[KlausST]

Hi,

//Set Timer Mode To Normal and Prescaler 1024 TCCR2=0b00000101;

Prescaler 1024 means 0b00000111

There is something wrong.

Klaus

 

[maxbayne]

thanks so much @KlausST
t

this is my fault i thought that all timer with same clock source configurations but iam wrong and you are correct
many thanks to you ... i have 2 weeks research for it and bought real hardware to test , i said may be proteus wrong ... thanks again

 

[willsonwanda]

What is the difference between TIMER0 and TIMER2?


Unlike other timers, TIMER2 offers us with a wide range of prescalers to choose from. In TIMER0/1 the prescalers available are 8, 64, 256 and 1024, whereas in TIMER2, we have 8, 32, 64, 128, 256 and 1024! Since we are choosing 256 as the prescaler, we choose the 7th option (110).