Servo Program Using TIMER0

[BhanuKiran Chaluvadi]

Hello sir , I have programmed servo using Timer0, Its not Working.I am unable to sort out mistake, Could u please Help me

 

 

#include <avr/io.h>

#include <util/delay.h>

#include <avr/interrupt.h>

 

volatile uint8_t tot_overflow;

 

void timer0_init()

{

TCCR0  |= (1<<WGM01) | (1<<WGM00) | (1<<CS12) ; // Fast PWM CTC mode, Prescaling of 256.

 

TCNT0 = 0 ;

OCR0 = 249;     //This gives us a time period of 4ms.

TIMSK  |= (1<<OCIE0) ;

sei();

 

}

ISR (TIMER0_COMPA_vect)

{

tot_overflow++;

if(tot_overflow==5)  //5 waves each of time period 4ms= 5*4=20ms

{

PORTA |= (1<<PA0) | (1<<PA1) | (1<<PA2) ;

tot_overflow=0;

}

 

}

 

int main (void)

{

DDRA |= (1<<PA0) | (1<<PA1) | (1<<PA2) ;

timer0_init();

  tot_overflow=0;

while(1)

{

if (TCNT0>=15 && TCNT0<=145 && tot_overflow==0 )

{

 

 

if (TCNT0 >= 23 && bit_is_set(PORTA, PINA0)  ) PORTA &= ~(1<<PINA0);

if (TCNT0 >= 78 && bit_is_set(PORTA, PINA1)  ) PORTA &= ~(1<<PINA1);

if (TCNT0 >= 133 && bit_is_set(PORTA, PINA2) ) PORTA&= ~(1<<PINA2);

 

}

}

 

}

[zaib Akhter]

where from this TCNT1 came?????????????

 

initialized only timer0 and using tcnt1 in main ………

[zaib Akhter]

TCNT1 is register of TIMER1

 

so you should either initialize timer1

 

OR

 

use TCNT0……………………………….

[BhanuKiran Chaluvadi]

Unfortunately, i posted it wrongly sir . In the actual program i  used TCNT0 every where. Now i corrected  the program posted above . Could u please help me in finding mistake sir .

[zaib Akhter]

for Timer0 ……………… ISR (TIMER0_COMP_vect)

if you are having problem with result then tell what you want… add some discription.

 

as it is producing some output and able to rotate motor in one direction

(i have not really work with servo so don’t know much)

[BhanuKiran Chaluvadi]

 

Thanks for u r  help sir …I made 2 mistakes

 

1.Using CS12 for Prescaling which has to be CS02 ;

 

2. It has to be  ISR(TIMER0_COMP_vect)   not  ISR(TIMER0_COMPA_vect) ;

[BhanuKiran Chaluvadi]

/* Here is the actual Working Progam, Controlling Servo Using TIMER0 . SO that we can  use Timer1 for other Purpose */

 

 

#include <avr/io.h>

#include <util/delay.h>

#include <avr/interrupt.h>

 

volatile uint8_t tot_overflow;

 

void timer0_init()

{

TCCR0  |= (1<<WGM01) | (1<<WGM00) | (1<<CS02) ; // Fast PWM CTC mode, Prescaling of 256

 

TCNT0 = 0 ;

OCR0 = 249;

TIMSK  |= (1<<OCIE0) ;

sei();

}

 

ISR (TIMER0_COMP_vect)

{

tot_overflow++;

if(tot_overflow==5)

{

PORTA |= (1<<PA0) | (1<<PA1) | (1<<PA2) ;

tot_overflow=0;

}

 

}

 

int main (void)

{

DDRA |= (1<<PA0) | (1<<PA1) | (1<<PA2) ;

timer0_init();

  tot_overflow=0;

while(1)

{

if (TCNT0>=15 && TCNT0<=145 && tot_overflow==0)

{

if (TCNT0 >= 23 && bit_is_set(PORTA, PINA0)  ) PORTA &= ~(1<<PINA0);

if (TCNT0 >= 78 && bit_is_set(PORTA, PINA1)  ) PORTA &= ~(1<<PINA1);

if (TCNT0 >= 133 && bit_is_set(PORTA, PINA2) ) PORTA &= ~(1<<PINA2);

 

}

}

 

}

[Jithin David]

Hi Bhanu

In above Program you have used three pins among them which pin used  for servo motor.

[Author]

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