AVR Freaks

[/code:1]

#include <avr/io.h>
#include "fuelgauge.h"


void main(void)
{

  unsigned char counter;

  init();				  // Initialize the controller

  TCCR0A |=  (1<< WGM01) | (0 << WGM00);

  OCR0A= 0xFF; 
  
  TCCR0B |= ((0 << CS02) | (0 << CS01) | (1 << CS00)); // Set up timer at Fcpu/1024

  
  for (;;) 
   { 

   counter=TCNT0;


   if (TIFR0 & (1 << OCF0A)) 
      { 
          PINB = 0x07; // Toggle the LED 

          TIFR0 = (1 << OCF0A);

	   }

   } 

}

void init(void)
{

  CLKPR = (1 << CLKPCE);
  CLKPR = 0;


  DDRB = (1 << PB0) | (1 << PB1) | (1 << PB2) | (1 << PB4) ;
  PORTB = (1<<PB0)|(1<<PB1)|(1<<PB2);
  PINB = 0x00;
}

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[code:1]

Let's go with the previous example in part two: a 1Hz flasher, using a 1MHz clock and a prescale of 64. We found the timer count to be 15625 for those conditions.

TCCR1B |= (1 << CS11); // Start timer at Fcpu/8 

//****************************************  
  TCCR1B = _BV(WGM12) + _BV(CS10);  // clear timer on compare match, no prescaler
  OCR1A  =  XTAL/DEBOUNCE;		   		// timer = 5 msec . 40000000/200 = 200000??
  TIMSK  = _BV(OCIE1A);            	// enable Output Compare 1 overflow interrupt
//****************************************

TIFR or TIFR1 depends on the AVR, Dean is writing for mega 16 where the register is shared between timers and is called TIFR.

#include  
#include  

int main (void) 
{ 
   	DDRD |= (1 << 6); // set port PD6 as output. (led-> Timer 0 output on port OC0A (PD6, pin 12))
   	DDRD |= (1 << 5); // set port PD5 as output. (led-> Timer 0 output on port OC0B (PD5, pin 11))
	DDRC |= (1 << 0);

// Waveform generation bits - see table 14-8 on page 104 of datasheet atmega168
// Configure timer 0 for CTC mode 
   	TCCR0B |= (0 << WGM02); 
   	TCCR0A |= (1 << WGM01) | (0 << WGM00);

   	OCR0A   = 10; // Set Clear Timer on Compare Match mode (CTC) value - also known as TOP
   	OCR0B   = 1;  // Set Clear Timer on Compare Match mode (CTC) value 

// set OC0A and OC0B to toggle on compare match. page 102/103
	TCCR0A |= ((1<< COM0A0) | (0 << COM0A1) | (1<< COM0B0) | (0 << COM0B1)); 

// Start timer at Fcpu/64 See prescaler table 14-9 on page 106
	TCCR0B |= ((1 << CS00) | (1 << CS01) | (0 << CS02)); 


	
   for (;;) 
   { 

   } 
} 

/*

PWM on atmega168 @ 10 MHz
two outputs OC0A (Port D6, pin 12) and OC0B (Port PD5, pin 11)

1) case WGM02=0 Mode 1 (table 14-8), PWM, Phase correct, TOP=0xFF

If WGM02=0 
Fixed freq: 39.0 kHz if fast is on (WGM01=1) or 19.6 kHz if fast is off (WGM01=0)
duty cycle set by OCR0A and OCR0B for both output ports.


2) case WGM02=1 Mode 5 (table 14-8), PWM, Phase correct, TOP=OCRA

If WGM02 = 1 then behavior is different: One (1) output only: OCR0B. Output OCR0A is constant high.
Frequency is determined by OCR0A: e.g.

OCR0A   = 100 : freq = 50.0 kHz (fast off)
OCR0A   = 200 : freq = 25.0 kHz (fast off)
OCR0A   = 100 : freq = 99.0 kHz (fast on)
OCR0A   = 200 : freq = 49.75 kHz (fast on)
OCR0A   = 199 : freq = 50.0 kHz (fast on)

The duty cycle of the output is: (OCR0B / OCR0A). 
e.g. OCR0A = 200, OCR0B = 35. Duty cycle=(35/200) * 100% = 17.5%

*/

#include  
#include  

int main (void) 
{ 
   	DDRD |= (1 << 6); // set port PD6 as output. (led-> Timer 0 output on port OC0A (PD6, pin 12))
   	DDRD |= (1 << 5); // set port PD5 as output. (led-> Timer 0 output on port OC0B (PD5, pin 11))
	DDRC |= (1 << 0);

// Waveform generation bits - see table 14-8 on page 104 of datasheet atmega168
// Configure timer 0 for PWM, Phase Correct 
   	TCCR0B |= (1 << WGM02); 
   	TCCR0A |= (0 << WGM01) | (1 << WGM00);

   	OCR0A   = 200; // Set Clear Timer on Compare Match mode (CTC) value - also known as TOP
   	OCR0B   = 9;  // Set Clear Timer on Compare Match mode (CTC) value 

// set OC0A and OC0B . page 102/103
	TCCR0A |= ((0<< COM0A0) | (1 << COM0A1) | (0<< COM0B0) | (1 << COM0B1)); 

// Start timer at Fcpu/1 See prescaler table 14-9 on page 106
	TCCR0B |= ((1 << CS00) | (0 << CS01) | (0 << CS02)); 


	
   for (;;) 
   { 
// Take a hike
   } 
} 

TCCR1B |= ( 1 << CS12) ; // set up timer at Fcpu/256
	for(;;)
	{	
		// Check timer value in if statement, true when count 			//matches 1 second
		if (TCNT1 >= 31250)
		{
			TCNT1 = 0; // Reset timer value 
         		ElapsedSeconds++;
			if ( ElapsedSeconds == 30 ) // Check if 1/2 minute 							    //has elapsed
			{
				
				ElapsedSeconds = 0; // Reset counter variable
				PORTC ^= ( 1 << 0);	//Toggle the LED
				
			}
		}
	}
	
}