setting PWM Counter and registers yields odd behavior

Using Arduino Programming Questions
1

tonights issue is the following ,
when trying to set up counter 0 which is an 8 bit counter
to fastPwM
i use the following code
now before you read
understand i have tried the following
Change the interrupt to overflow , on compare match

also tried having no interrupt and just updating the compare register everytime i update pwm

but the strange behavior is this..
it does what i want it to do but...wrong
i want it to fade in and out out

instead it fades from 0 to 255 THREE TIMES
and then from 255 to 0 THREE TIMES...
where in the code am i telling it do it three times in between transitions ????

i want one fade up and one fade down nice smooth transition..

unless i have a misunderstanding of how the timer works

int main(void)
{	

        sei(); //global interrupts
	DDRD |=(1<<PIND6); // set pin d6  OC0A to output
	
	
	
	TCCR0A |= ((1<<WGM01) | (1<<WGM00)); // enable fast pwm 
	
	TCCR0A |= (1<<COM0A1); // clear on compare math , set at bottom
	TIMSK0 |= (1<<OCIE0A);// compare match interrupt
       
	
	OCR0A = ((pwm / 100) * 255.0 ) ;//value to compare to timer , aka pwm dudty cycle 
	TCCR0B |= (1<<CS00) ); // no prescale 
	
	
	while(1)
	{
		_delay_ms(10);
		//just fade in and out , 8 bit mode
		if (pwm >=255)
		cycle = 0;
		
		
		if(pwm <=1 )  
		cycle = 1; 
		
		if(cycle == 0 )
		pwm --;
		
		if (cycle == 1)
		pwm++;
		
		
	}
	
}
ISR (TIMER0_COMPA_vect)
{
	OCR0A =  ((pwm / 100) * 255.0 ); // update  duty cycle again since it changes everytime around main loop
	
	
}
2

interesting..i think its because of delay but then again it would happen every 10ms if it was indeed delay

its goes
0...255
0...255
0...255
255...0
255...0
255...0

not at all what it want
any ideas?

3

That doesn't compile. Where is pwm declared?

4

sorry i didnt include the preprocessor code in my post

but i have pwm set as a global since its used all over the place

double  pwm = 0;
int cycle = 0;
5

How did you get past

TCCR0B |= (1<<CS00) ); // no prescale