PWM duty cycle change

Hardware Arduino Due
1

Hi,

I'm tryng to have Arduino Due generate a PWM with fixed frequency but sine modulated duty cycle.

I would like to attach the PWM duty cycle change to PWM generation timer interrupt.

So far I add a look at many forums but I couldn't find any way to do that.

Can you give any advice?

Thanks in advance!

Garvano

2

You mean doing DDS (direct digital synthesis) in a timer overflow interrupt something like this:

#define MASK 0xFF
#define SHIFT 8
float sinetable [0x100] ;
volatile int phase ;
volatile int freq ;

ISR (TIMER1_OVF_vect)
{
  phase += freq ;
  OCR1A = 128 + 127 * sinetable [(phase>>SHIFT) & mask] ;  // DDS 
}

(In practice an integer table, not float, would be used for speed)