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Timer0 counter


Timer 0 interrupt counter

Toolkit:AVR Development System

Location:/bipom/devtools/WinAVR/minimaxavrc/Examples/Labs/Lab06/Lab6_3

Code Example


#define ONE_SECOND 		500
#define HALF_SECOND 	250

#define LED_RED          6        //PB6

#define LED_YELLOW       4        //PB4

#define LED_GREEN        5        //PB5


#define LED_RED_ON() 		(PORTB	&=~ 0x40)
#define LED_YELLOW_ON()  	(PORTB	&=~ 0x10)
#define LED_GREEN_ON()  	(PORTB	&=~ 0x20)

#define LED_RED_OFF() 	    (PORTB	|= 0x40)
#define LED_YELLOW_OFF()   	(PORTB	|= 0x10)
#define LED_GREEN_OFF()   	(PORTB	|= 0x20)

unsigned int counter = 5 ;
unsigned int Ticks = 0 ;

unsigned int RedFlag,YellowFlag;         // Flag for Red LED state


ISR (TIMER0_OVF_vect)
{
	// Interrupt every 2 mS


if(Ticks == HALF_SECOND)
	{
		if(RedFlag)   // checking Red LED state

		{
			RedFlag=0;
			LED_RED_ON(); // Turn on RED LED

		}
		else
		{
			RedFlag=1;
			LED_RED_OFF();// Turn off RED LED 

		}
	
		counter++; 
		if(counter > 20) // checking counter value

		{
			if(YellowFlag) // check Yellow LED state 

			{
				YellowFlag=0;
				LED_YELLOW_ON(); // Turn on YELLOW LED

			}
			else
			{
				YellowFlag=1;
				LED_YELLOW_OFF();// Turn off YELLOW LED

			}
		}
		Ticks = 0;
	}
	Ticks++;
}

int main(void)
{

	//Initialize port pins

 	/* Define pull-ups and set outputs */
	/* Define directions for port pins */
	PORTB = (1<<LED_RED)|(1<<LED_YELLOW)|(1<<LED_GREEN);
	DDRB  = (1<<LED_RED)|(1<<LED_YELLOW)|(1<<LED_GREEN);

	//Initialization Timer0

	// Timer/Counter 0 initialization

	// Clock source: System Clock

	// Clock value: 125,000 kHz

	// Interrupt every 2mS

	TCCR0A=0x00;
	TCCR0B=0x03;
	TCNT0=0x00;
	OCR0A=0x00;
	OCR0B=0x00;	

	//Timer0 Overflow Interrupt Enable													

	TIMSK0 = 0x01;
	Ticks=0;
	
	// Global enable interrupts

	sei();
	while (1) ;
}