PWM Generation Using ATMEGA16 Microcontroller code

Timer:

·         Timer in simple terms is a register.

·         It can hold 8 or 16 bit data.

·         There are 3 timers i-e timer0,timer1 & timer2.

·         Timer0 & timer2 are 8 bit while timer1 is 16 bit.

·         We have used used timer0 & timer2 to generate PWM i-e one timer for one set of H-bridge switches.

8 Bit Timer Registers:

There are 3 different registers for 8 bit timers:

1.      TCCR(Timer Counter Control Register):

·         It selects the mode of operation, clock source & prescalars for the timer.

·         We have used internal clock with a prescalar of 8.

2.      TCNT(Timer Counter Register):

It holds the value of timer count.

3.      TIMSK(Timer/Counter Interrupt Mask Register):

It contains interrupt control bits for all 3 timers.

Code:

#include <mega16.h>

#include <delay.h>

unsigned char display [100] ={0xfa,0xf9,0xf8,0xf7,0xf6,0xf4,0xf2,0xf0,0xee,0xeb,0xe8,0xe5,0xe2,0xdf,0xdb,0xd7,0xd3,0xcf,0xca,0xc6,0xc1,0xbc,0xb6,0xb1,0xab,0xa5,0x9f,0x99,0x93,0x8d,0x86,0x7f,0x78,0x71,0x6a,0x63,0x5c,0x55,0x4d,0x46,0x3e,0x37,0x2f,0x27,0x1f,0x18,0x10,0x08,0x00,0x00,0x08,0x10,0x18,0x1f,0x27,0x2f,0x37,0x3e,0x46,0x4d,0x55,0x5c,0x63,0x6a,0x71,0x78,0x7f,0x86,0x8d,0x93,0x99,0x9f,0xa5,0xab,0xb1,0xb6,0xbc,0xc1,0xc6,0xca,0xcf,0xd3,0xd7,0xdb,0xdf,0xe2,0xe5,0xe8,0xeb,0xee,0xf0,0xf2,0xf4,0xf6,0xf7,0xf8,0xf9,0xfa};

interrupt [TIM0_OVF] void timer0_ovf_isr(void)

{ static int i=1;

PORTC.1=~PORTC.1;

TCNT0= display[i];

i++;

if(i==98)

{ i=1;

PORTC.1=0;

TCCR0=0x00;

TCCR2=0x02;

TCNT2=0xfa;

TIMSK=0x40;

#asm("sei")

}

}

interrupt [TIM2_OVF] void timer2_ovf_isr(void)

{ static int j=1;

PORTC.2=~PORTC.2;

TCNT2= display[j];

j++;

if(j==98)

{ j=1;

PORTC.2=0;

TCCR2=0x00;

TCCR0=0x02;

TCNT0=0xfa;

TIMSK=0x01;

#asm("sei")

}

}

void main(void)

{

DDRC=0xff;

PORTC=0x00;

TCCR0=0x02;

TCNT0=0xfa;

TIMSK=0x01;

#asm ("sei")

while(1)

{

}

}