Atmega88 und Fast PWM Mode14. Ein Drama

/*

 Hardware

 ATMEGA88, Takt 8 Mhz intern

 Output OC1A 

*/

#include <avr/io.h>

#include <avr/interrupt.h>

#define CHANNELS 4

volatile uint16_t port[ CHANNELS];

volatile uint16_t pause = 0;

volatile uint16_t sync_len = 200;  // 0,2ms

volatile uint16_t per_len = 9000;  // Gesamt-Laenge

volatile uint8_t active = 0;       // aktueller Port

volatile uint8_t channels = CHANNELS;

volatile uint16_t counter = 0;

ISR( TIMER1_OVF_vect) 

{

 OCR1A = port[ active];

 if( active != channels -1)

  ICR1  = OCR1A + sync_len;

 else

   ICR1 = OCR1A + per_len - ((channels-1) * sync_len) - pause;

 if( active == 0) // erster Port

 {

  pause = port[ active];

  ++counter;

 }

 else

 {

  pause += port[ active];

 }

 active = (active+1) % channels; // active = 0 - 3

} // ISR

int main( void)

{

 uint8_t i = 0;

 uint16_t t ;

 for( i = 0; i < 4; ++i)

 {

  port[ i] = 800;

 }

 DDRB = (1 << DDB1); // OC1A auf output

 TCCR1A = ( 1<< COM1A1)| ( 1<< COM1A0)| ( 1<< WGM11);

 TCCR1B = ( 1<< WGM13) | ( 1<< WGM12) | ( 1<< CS11); // Teiler/8

 TCCR1C = 0;

 OCR1A = port[ 0];

 ICR1  = OCR1A + sync_len;

 TIFR1  = (1 << TOV1);//| (1 << OCF1A);

 TIMSK1 = (1 << TOIE1);

 sei();

 t = counter;

 i = 0;

 while (1)

 {

  if( counter - t == 40) // kleines test

  {

   cli();

   port[ 1] = 900 + (((++i) % 2)? 0 : 400);

   sei();

   t = counter;

  } // if

 } // while

 return 0;

}